Digestibility of Proteins in Legumes

*Stephanie A. Misquitta, Deepika N. Kshirsagar, Pooja R. Dange, Vikram G. Choudhari and Mukund M. Kabra*

#### **Abstract**

Legume proteins have recently attracted interest from the food industry. Indeed, they are economical and have good nutritional and functional attributes. In addition to being important for growth and maintenance, they also provide antioxidant peptides, and are hence gaining importance for these additional health benefits. The nutritional benefits of leguminous seeds, are linked to the digestibility of the proteins into peptides and amino acids. Seed proteins have a complex structure. Coexisting with these proteins in the seed matrix, are other components that interfere with protein digestibility. Among them, are the antinutritional factors (ANFs), like trypsin inhibitors, which are also significant in animal nutrition. Thus, improving access to legume proteins, often depends on the removal of these inhibitors. Therefore, this chapter focuses on the factors affecting the efficient digestion of proteins, with emphasis on ANFs and methods to eliminate them. Enzymatic treatment is an effective method to solve the problems encountered. Exogenous enzymes, act as digestive aids and help improve protein digestibility *in vivo*, where digestion is impaired due to insufficient digestive enzymes. Enzymes provide an environment-friendly alternative to energyintensive processes in the food industry. Complete digestion of legumes will prevent wastage and enhance food security, besides contributing to sustainability.

**Keywords:** protein digestibility, antinutritional factors, trypsin inhibitors, enzymes, proteases

#### **1. Introduction**

The origin of legumes in the diet of human beings, dates back to ancient times. The discovery of what is believed to be a pigeonpea in an Egyptian tomb, lead us to believe that lentils were used as food thousands of years ago. What was part of the diet of the ancient Aztec, Inca, Greek, Egyptian and Indian Vedic cultures, continues to hold importance even in today's modern world. For centuries now, legumes have been consumed by people all over the world. Globally, grain legumes occupied 81 million ha with production of more than 92 million tonnes. Major grain legume producing countries are India, China, Myanmar, Canada, Australia, Brazil, Argentina, USA and Russia [1]. Among the legumes consumed by humans, soyabean is by far the most widely used. Referred to as "poor man's food", pulses and beans are part of the staple diet among the low-income population, as they are used as a main source of protein, instead of animal meat, which has traditionally been more expensive and not as easily available. They have emerged as effective tools in the fight against global malnourishment. Most health organizations recommend consuming vegetable protein on a regular basis, as it has been shown to lower blood cholesterol levels, the risk of coronary heart disease, and diabetes [2]. According to Dietary guidelines for Americans, U.S. Department of Agriculture, and U.S. Department of Health and Services, legumes should be included several times a week, in the diet.

Apart from being used as a protein source for the diet, legumes have other health benefits that are only now being realized. However, the digestibility of plant seed proteins is low, as compared to animal proteins. Hence it is important to understand the factors influencing the complete breakdown of proteins into their constituent components, so that remedial measures can be undertaken to maximize their use in food or in food applications.

#### **2. Health benefits of legumes**

The nutritional value of legumes was recognized in ancient cultures. Fava beans were used in recipes, in what is claimed to be the oldest cookbook during the Roman civilization. For human nutrition, approximately 20 leguminous species are employed as dry grains. Among the legumes used, the most common one is soyabean, followed by lentil, chickpea, and cowpea, with soyabean being the most important, due to its high protein content (**Table 1**).


#### **Table 1.**

*Crude protein content of commonly used legumes.*

In comparison to animal protein sources, legume seeds are high in dietary fiber, which is good for gut health [7]. They possess high nutritional value. Legumes are rich sources of good quality proteins, calories, certain minerals, fibers, vitamins and are cholesterol free. Thus, legumes have the potential to increase the nutritional quality of foods, and hence, efforts are underway for their integration into novel food preparations with improved nutritional and functional qualities [8].

Proteins or peptides derived from legumes have played a significant role, beyond simply providing amino acids for growth and tissue repair. The role of legume proteins in the general growth and maintenance of living organisms is well documented. However, little is known about the beneficial effects of peptides derived from legumes.

#### **2.1 Antioxidant property of peptides**

Bioactive peptides are amino acid sequences, that exert beneficial effects in the body to improve human health beyond their nutritional values [9, 10]. These peptides can have antioxidative, antimicrobial, anticarcinogenic, or anti-inflammatory activities, based on their sequence and size. The antioxidant activity can be defined as metal *Digestibility of Proteins in Legumes DOI: http://dx.doi.org/10.5772/intechopen.110372*

chelating or radical scavenging properties, which have a direct or indirect impact on the inhibition of free radical generation. Intake of such bioactive peptides can minimize the risk of chronic diseases [11, 12].

Environment-friendly processes like enzymatic hydrolysis are preferred to chemical hydrolysis as it results in bioactive peptides [13, 14]. The most frequently used commercial proteolytic enzymes are papain, pancreatin, trypsin, chymotrypsin, and bromelain. The high antioxidant activity of soy hydrolysate obtained after proteolytic digestion has been well documented earlier [15]. In a recent study, an enzyme formulation, PepzymeAG has been shown, to not only improve the digestion of pea protein, but also result in peptides with antioxidant and antidiabetic properties [16]. Peptides are therefore gaining importance and their use is expanding, in nutraceuticals and pharmaceuticals products.

Antioxidant properties of peptides can be assessed by different methods viz. DPPH (2,2-diphenyl-1-picrylhydrazyl), ABTS (2,2<sup>0</sup> -azino-bis(3-ethylbenzothiazoline-6-sulfonate) etc. Purification and identification of specific peptides and/or amino acids with antioxidant activities are needed to expand their application in the food and pharmaceutical industries.

#### **3. Digestion of proteins into amino acids**

Proteins cannot be absorbed by the digestive tract as is. Several proteolytic enzymes are at play in the digestive system of mammals. In the acidic condition of the stomach, pepsin has optimum activity. The pancreas secrete proteolytic enzymes, like trypsin and chymotrypsin, which function at a higher pH of 8–9. Due to the action of these proteolytic enzymes, proteins are digested into oligopeptides and then amino acids (**Figure 1**). The amino acids available are of great importance in nutrition.

**Figure 1.** *Digestion of proteins into peptides and amino acids.*

#### **3.1 Essential amino acids**

An essential amino acid, or indispensable amino acid, is an amino acid that cannot be synthesized from scratch by the organism fast enough to supply its demand, and must therefore come from the diet. The essential amino acids (EAAs), (e.g., arginine, methionine, lysine, leucine, isoleucine, tryptophan, valine, threonine, phenylalanine, and histidine) cannot be produced endogenously, so 10–20 mg/kg body weight of each must be obtained in the diet each day from consumed protein [17]. Moreover, dietary protein sources must provide the whole range of EAAs since proteins deficient in one or more EAAs generate an unpleasant eating response, resulting in a

**Figure 2.** *Hydrophobic essential amino acid profile in different legumes.*

**Figure 3.** *Hydrophilic essential amino acid profile in different legumes.*

considerable decline in diet consumption. **Figures 2** and **3** illustrate all the hydrophobic and hydrophilic essential amino acids, present in easily accessible legumes such as soyabean, chickpea, cow pea, and lentils.

*Digestibility of Proteins in Legumes DOI: http://dx.doi.org/10.5772/intechopen.110372*

The following percent of their contents in soyabean grain are documented in the reference literature: Leucine is approximately 7.6% of crude protein and lysine is about 6.3% of crude protein whereas valine, isoleucine and phenylalanine are around 4.7% each, of crude protein [18]. When compared to animal proteins, soyabean protein has a lower amount of sulfur containing amino acids. Legume proteins, with the exception of soyabean (*Glycine max*), are considered incomplete due to a lack of key sulfur-containing amino acids (methionine and cysteine). To compensate for this deficiency, legume proteins are supplemented with cereal proteins, which are low in lysine but high in methionine and cysteine [3].

#### **3.2 Protein digestibility evaluation method**

Although legume-derived proteins are nutritionally adequate, their protein quality and digestibility remain an issue [19]. WHO recommends that in order to support optimal health and growth, humans should consume high quality proteins [20]. Protein quality is the ability of dietary proteins to fulfill the metabolic needs of the body, thus quality matrices are governed by the content of limiting amino acids in food and their digestibility [21]. Limiting amino acids are those amino acids that do not meet the minimal requirement of the body and need to be included in a diet.

Different regulatory bodies across the world (US-FDA, Canadian food inspection agency) use protein quality information to determine 'Protein Digestibility'. From a consumer point of view, protein quality claims can influence the perception of health benefits of the product. Therefore, nowadays, commercial protein powders often provide protein content claims in the form of a digestibility score.

Protein digestibility can be defined as the fraction of protein that is available for absorption after it is ingested. It is a measure of the bioavailability of the protein. High digestibility is dependent on the hydrolysis of peptide bonds that are characteristic of proteins. The digestibility of plant proteins is lower (<80%) than animal proteins (≥90%) [22]. A joint FAO/WHO (Food and Agricultural organization/ World Health Organization) expert consultation committee proposed the first method for protein quality evaluation in 1990, the Protein digestibility-corrected amino acid score (PDCAAS).

PDCAAS% <sup>¼</sup> ð Þ mg of first limiting amino acid in 1 g test protein ð Þ mg of the same amino acid in 1 g reference protein � TD � <sup>100</sup>

Here, true digestibility TD ð Þ¼ <sup>I</sup>�F�Fk I

I = protein intake of rats fed Test diet

F = protein excreted in feces of rats fed Test diet

Fk = protein excreted of rats fed protein-free diet.

However, in 2011, FAO/WHO made a recommendation that the new protein quality measure (digestible indispensable amino acid score; DIAAS) replace the old PDCAAS.

DIAAS% <sup>¼</sup> <sup>ð</sup>mg of digestable dietary indispensable amino acid in 1 g of the dietary protein<sup>Þ</sup> ðmg of the same dietary indispensable amino acid in 1 g of the reference proteinÞ � 100

There are many reasons why this shift has been recommended, two of them were the superior scoring method and the accurate sampling method [23–25]. For instance, the PDCAAS score of Whey Protein Isolate (WPI) and Soy Protein Isolate (SPI) is 1 and 0.98 (no significant difference). But the DIAAS score of WPI's is 1.09 and for SPI it reduces to 0.90. This gives a clear distinction of protein quality and in turn helps to make informed decisions. Knowledge of the IAA (Indispensable amino acid) content from protein sources, is not sufficient to accurately determine the requirement of the type of amino acid, because it varies with respect to physiological conditions, age etc. Therefore, FAO concludes that the current data of digestibility is insufficient and suggests that additional data is required, on ileal digestibility of human foods, determined in animal as well as human models [25].

Other alternate ways to determine protein digestibility, such as *in vitro* digestion methods that are less time consuming, controllable and easy to perform are INFOGEST, and *in vitro* PDCAAS [26, 27]. In a recent study, INFOGEST was used to study the digestion of pea proteins using enzymes under simulated gastrointestinal conditions [16].

#### **4. Factors affecting protein digestibility (extrinsic and intrinsic factors)**

The full benefits of legumes depend on how easily the proteins are digested. Proteins are polymers of amino acids. Amino acids are linked together by a peptide bond formed between the amino group of one amino acid and the carboxyl group of the adjacent amino acid. The sequence of amino acids defines its primary structure. The organization of amino acids into secondary and tertiary structures is what defines the ultimate protein structure, an attribute that is unique and dependent on the primary structure. The polypeptide chain is not linear, but adopts a three-dimensional structure and can be interlinked via disulphide bonds, making for a stable structure. Breakdown of this structure is required before peptides or amino acids can be released, either by internal digestion or by processing methods.

Different legumes contain different types of proteins. Hence, the increase in digestibility of legume proteins varies, depending on the type of protein they contain. When compared to animal proteins, the digestibility of legume protein is low. Among legumes, there are variances in the digestibility of proteins, with ease of digestibility increasing in the following order: soyabean, lentil, chickpea and common bean [7, 8]. Protein structure and functionality, compartmentalization, the permeability of cell walls, the protective seed coat, and enzyme accessibility are all important aspects of this trait.

The digestibility of proteins, can be influenced by several factors that can be classified as extrinsic factors or intrinsic factors. Extrinsic factors include pH, temperature, ionic strength conditions, and the food matrix, as well as the presence of secondary molecules present in the environment of the protein. Intrinsic factors are those factors that contribute to the inherent property of the protein, and impart its characteristics. These include protein amino acid sequence and protein structural characteristics. Furthermore, growth conditions (e.g., drought and heat stress) can influence both internal and exterior elements throughout plant development [28, 29]. The pre-harvest characteristics influencing plant protein digestibility, on the other hand, are beyond the scope of this chapter.

#### **4.1 Extrinsic factors**

Extrinsic factors can affect the digestibility of legume proteins: these include interaction with other compounds such as carbohydrates, lipids, and antinutritional

#### *Digestibility of Proteins in Legumes DOI: http://dx.doi.org/10.5772/intechopen.110372*

factors like tannins, phytates, trypsin inhibitors and lectins. These are described in detail, in another section in this chapter. In the seed matrix, proteins are complexed with other compounds like phenolic compounds and carbohydrates, causing a physical entrapment of cellular structures that shield the proteins from the action of proteases. Drulyte et al. suggested that cell wall rigidity and fiber content may influence protein digestibility. Particle size reduction disrupts the cell wall integrity; thus, the reported improvement of digestibility attributed to milling could also be due to the alteration of the cell wall, which enhances legume seed protein digestibility [30]. In a study, by Melito et al., physical or enzymatic removal of the cell walls enhanced legume digestion by up to 50%. This shows that physiological barriers such as the cell wall have an impact on protein digestion [31].

#### **4.2 Intrinsic factors**

The low digestibility of legume proteins is attributed to their amino acid composition and protein quaternary structure. Proline-rich regions often diminish protein chain flexibility and are renowned for their high resistance to peptidase hydrolysis. Legume seed storage proteins are classified into globulins, albumins, glutelins, and prolamins according to their solubility properties in water, salted water, or ethanol/water solutions. Among these, globulins and albumins are the most abundant proteins found in legumes. Albumins are soluble in water. Examples of albumin proteins are Kunitz trypsin inhibitor and Bowman-Birk trypsin/chymotrypsin inhibitors [8].

Globulins are extracted in salt solutions, and represent approximately 70% of legume seed proteins. They consist mainly of the 7S proteins called vicilins, and 11S proteins called legumins, [32]. Soyabean protein contains three major fractions such as 2S, 7S, and 11S. In soyabean, 11S and 7S fractions represent approximately 70% of total protein. 11S fraction consists only of glycinin, which typically exists as a hexamer and 7S fraction majorly consists of β-conglycinin. The molecular weight of seed proteins ranges from 8 to 600 kDa [33]. Albumins have a molecular weight ranging from 50 to 80 kDa. These proteins generally exist in oligomeric form. The 7S globulins are typically trimers of molecular weight about 150 kDa, while the 11S proteins form hexamers of molecular weight about 350–400 kDa, or higher association of subunits, such as the 15–18S globulins found in soyabean globulins [34].

One of the factors influencing the stability of proteins, is their secondary structure. In legumes proteins, the predominant secondary structure is the β-sheet conformation, as compared to the α-helix structure [35]. This β-sheet conformation contributes to its resistance to proteolysis in the gastrointestinal tract. The β-sheet structure of legume proteins is a contributing factor to aggregation which occurs during the processing of legume proteins. Protein aggregation affects the biological value and technological usefulness of the raw materials when used in food production. Another contributing factor to increased stability is the presence of disulphide bonds, formed between the polypeptide chains. Globulins showed better *in vitro* digestibility than albumins due to the presence of lower cysteine content and hence less number of disulphide bond as compared to albumins [7, 36].

The amino acid sequence of a protein determines the type of peptides formed on digestion. Peptidases have a high specificity for hydrolysing peptide bonds that are next to a specific type of amino acid. In processing, the sequence of peptides formed, depends on the legume protein used, and the specificity of the enzyme used. This determines the antioxidant activity of the resultant peptide. **Figure 4** shows an outline for the production of peptides, produced by enzymatic methods.

#### **Figure 4.**

*Digestion of proteins into peptides by specific enzymes and selection for antioxidant property.* Abbreviations*: E (different enzymes), UF (ultrafiltration), SEC (size-exclusion chromatography), DPPH (2,2-diphenyl-1 picrylhydrazyl), ABTS (2,2*<sup>0</sup> *-azino-bis,3-ethyl benzoline-6-sulfonic acid), HRSA (hydroxyl radical scavenging activity).*

#### **5. Enhancement of protein digestibility using enzymatic treatment**

Protein hydrolysis includes the breakage of peptide bonds, resulting in smaller peptides and free amino acids, which improves digestibility and functional characteristics [37]. Chemical hydrolysis (by acids or alkalis) has significant drawbacks since it can produce harmful amino acid residues (e.g., lysinoalanine) and produce goods with lower nutritional quality [38, 39]. Protein enzymatic hydrolysis by enzymes was previously used in the food industry to enhance the biological value and functional qualities of these molecules [40]. Protein hydrolysates produced by enzymatic treatment (e.g., cellulases, hemicellulases, proteases) may improve protein availability and digestibility by reducing undesired compounds found in legumes [38, 40, 41]. Proteases (or peptidases) have been used to improve product nutritional value by modifying protein structures [39, 42]. Protein hydrolysis has been shown to lower protein antigenicity, increase tolerance, and create peptides that do not stimulate *in vitro* IgE antibody binding activity, therefore decreasing allergenicity.

Protein enzymatic hydrolysis was found to be effective in enhancing protein solubility, foaming capacity and stability, and gelation capability [38, 39]. However, there are some challenges with the application of protein hydrolysates, because protein hydrolysis can result in the formation of hydrophobic peptides, which causes the development of bitterness and off-flavors, negatively impacting taste and limiting the use of protein hydrolysates in food products [37].

To improve the availability of protein in fava beans, enzymatic treatments were performed in four cultivars (ON, OPNS, TAL and VC3). The greatest change was observed in the OPNS cultivar treated with protease, which increased its digestibility from 54.4% (control treatment) to 81.6% [40]. Legume preparations when treated with pepsin/pancreatin in an *in vitro* digestion simulation, have resulted in 20–46% increase in the degree of hydrolysis [43].

#### **6. Problems encountered in the digestion of legumes**

#### **6.1 Insufficient digestive enzymes**

Digestive enzymes are synthesized by the stomach, small intestine, and pancreas. The pancreas have an essential role in the digestion, absorption, and metabolism of carbohydrates, fats, and proteins hence is the enzyme "powerhouse" of digestion. Insufficient secretion of digestive enzymes by the pancreas is called exocrine pancreatic insufficiency. Some enzyme insufficiencies are genetic, hereditary and congenital or develop over time, and with age. Any impairment of digestive enzymes over a prolonged period results in deficiencies of vitamins and minerals, gastrointestinal irritation, malnutrition, and complications, leading to poor quality of life.

Impaired enzyme-related digestion can be alleviated by prescription digestive enzymes. These over-the-counter digestive enzyme supplements are used to treat health issues such as acid reflux, gas, bloating and diarrhea. Enzyme supplements, like VegPeptase™ can be used to improve the digestibility of legumes. These supplements aid in better digestion of "hard-to-digest" proteins in food and absorption of nutrients. Pancreatic enzyme replacement therapy is the most popular and the only FDA-approved enzyme replacement therapy (PERT). PERT is the use of medications that contain enzymes to replace what the pancreas is deficient in producing. These medications contain proteases, amylases and lipases. Microbial sources of enzymes viz. cellulase, protease, and lipase can be used to improve digestion and access the required nutrients, when shifting to a plant-based diet. Similarly, plantsourced enzymes like bromelain (from pineapple) and papain (from papaya) are proteolytic enzymes, which are included in many digestive formulas. They have an additional use as systemic enzymes and against inflammation. This helps people follow a less restricted diet on a long term basis.

#### **6.2 Antinutritional factors (ANFs)**

One of the main factors affecting the protein digestibility of legumes is the presence of antinutritional factors. Antinutritional factors are compounds that are known to affect the digestibility and thus impair the nutritional quality of various foods, including legume food proteins [44]. These antinutritional factors are present in unprocessed food or foods, as a result of processing (e.g., Maillard reaction products in soyabean-based products) [45]. Major antinutritional factors, which are found in legumes include saponins, tannins, phytic acid, gossypol, lectins, protease inhibitors, amylase inhibitors, and goitrogens [46]. These antinutritional factors cause unfavorable effects when consumed in large quantities. They are also known to cause allergic responses in some individuals, which is a cause for concern [47]. Thus, the exclusion or deactivation of these antinutritional factors and allergenic compounds can promote protein digestibility.

Among the ANFs found in legumes, the following are known to interfere with protein digestion in humans and animals: protease inhibitors (trypsin inhibitors), tannins, lectins, and phytic acid (**Figure 5**).

#### *6.2.1 Protease inhibitors (trypsin inhibitors)*

One of the main ANFs found in legumes are protease inhibitors. They are small proteins, which have evolved as defense strategies in plants [48]. As the name

#### **Figure 5.**

*Antinutritional factors that interfere in protein digestion.*

suggests, these inhibitors inhibit the action of proteases in mammals, thus impairing protein digestion [49] and affecting the nutritional value of foods [50].

Trypsin and chymotrypsin are the main proteases, in the lumen of the upper gastrointestinal tract, where they exercise their digestive functions [51]. The presence of trypsin inhibitors in the diet leads to the formation of irreversible enzyme-trypsin inhibitor complexes. These complexes are indigestible, even in the presence of high amounts of digestive enzymes [52]. Trypsin inhibitors block the active site of trypsin/ chymotrypsin, through the N- or C-terminus and exposed loop [51], effectively preventing these enzymes from acting on the protein substrate (**Figure 6**). Therefore, when legumes are eaten raw or without being cooked properly, they upset digestive functions and cause diarrhea or excessive gas [52]. In such cases, even

#### **Figure 7.**

*Protein structure of trypsin inhibitors, (i) Bowman-Birk inhibitor (BBI), and (ii) Kunitz-type inhibitor, from soyabean. Images are prepared using PDB ids, 1BBI and 6NTT, using YASARA, version 22.9.24. The beta sheets are depicted in red.*


#### **Table 2.**

*Antinutritional factors in raw soyabean seeds [58].*

though the intake of protein is high, the complete mobilization of amino acids is prevented.

In legumes, the trypsin inhibitor content ranges from 3 to 84 U/mg, while the chymotrypsin inhibitor content varies from 0 to 17 U/mg [53, 54]. The prominent trypsin inhibitors in legumes are the Bowman-Birk inhibitor and Kunitz-type inhibitor (**Figure 7**) [55–57]. Kunitz-type inhibitor (molecular weight 18–24 kDa) and Bowman-Birk inhibitors (molecular weight 7–9 kDa) are both capable of inhibiting trypsin and chymotrypsin enzymes. In soyabeans, glycinin and β-conglycinin constitute 65–80% of the protein fraction or 25–35% of the soya seed weight (**Table 2**) [59]. Because of their predominant beta-barrel structure, they are very stable.

#### *6.2.2 Lectins*

Lectins are proteins that have specificity for carbohydrates. When combined with the glycoprotein components of red blood cells, they cause agglutination of the cells. Lectins bind to epithelial membrane of glycoproteins, such as brush-border membrane enzymes, gangliosides, glycolipids, receptors, secreted mucins, and transport proteins [60]. They disturb intestinal permeability and interfere with the absorption of digestive end products in the small intestine [61]. Protein digestion is affected, leading to nitrogen loss; the undigested and unabsorbed proteins in the small

intestines reach the colon where they are fermented to short chain fatty acids and release gases leading to gastrointestinal disorders. The affected intestinal permeability allows the entrance of the bacteria and their endotoxins into the bloodstream, causing a toxic response. Moreover, lectins may also be internalized directly and cause systemic effects. They can disrupt protein, carbohydrate, and lipid metabolism [62]. Lectins are also resistant to heat and digestive processes, during their intestinal passage their activity is retained [63].

#### *6.2.3 Phytic acid*

Phytic acid (myo-inositol-1,2,3,4,5,6-hexakis dihydrogen phosphate) (**Figure 8a**), is a secondary compound found in plant seeds of legumes [64]. Generally, phytates contain about 50–80% of the total phosphorus present in the seeds [65]. Due to its chelating property, phytic acid complexes with metal ions, like iron, magnesium and calcium, reducing their bioavailability, and resulting in mineral ion deficiencies in human nutrition [66, 67]. In addition, phytic acid interferes with the digestion of proteins. In both acidic and basic pH, phytic acid forms a complex with proteins and alters the protein conformation. It also binds trypsin and thus affects the action of trypsin on proteins [68–70].

#### *6.2.4 Tannins*

Tannins are located in the layer between the external tegument and the aleuronic layer inside the seeds, protecting the plant embryo from mechanical and oxidative damage and maintaining its dormancy [71]. They are also present in plant leaves, fruits, and bark [72].

The consumption of tannins can cause hardening of the gastrointestinal mucosa, resulting in reduced nutrient absorption. Tannins affect protein digestibility, by forming reversible and irreversible complexes between the hydroxyl group of tannins (**Figure 8b**) and the carbonyl group of proteins, leading to a decrease in essential amino acid availability [28, 73, 74]. These complexes are relatively large and hydrophobic in nature [75]. The breakdown products constitute a large number of compounds, which can be toxic. In the oral cavity, tannins bind to proline-rich proteins in saliva, and this helps to protect dietary and endogenous protein. However, in the

**Figure 8.**

*(a) Chemical structure of phytic acid (b) Chemical structure (basic unit) of tannin. (chemical structures are prepared using Marvin JS).*

absence of sufficient salivary secretion, tannins are then free to interact with digestive enzymes [76, 77]. Tannins are known to inhibit the digestion of proteins by 28% [46].

#### **6.3 Methods to eliminate antinutritional factors**

Some of the common methods employed to diminish or eliminate antinutritional factors include soaking, heating, cooking, germination, fermentation, extraction, irradiation, and enzymatic treatment [78]. The application of a single technique is frequently insufficient for effective treatment and so combinations of methods are usually employed. These treatments can be classified based on the processing techniques—physical, chemical, biological and enzymatic.

#### *6.3.1 Physical treatment*

Soaking overnight is the most common method used to reduce the antinutritional content in legumes and improve their nutritional value. Most of the antinutrients in these foods are found in the upper layer. Since many are water-soluble, they can be eliminated by prolonged soaking. In legumes, soaking has been found to decrease phytate, protease inhibitors, lectins, and tannins. Soaking is typically used in combination with other methods, like thermal treatment, germination, and fermentation.

Thermal treatments, like cooking, boiling, autoclaving and microwave cooking are the most popular methods for processing legumes, because it improves protein digestibility. Processing by heat is an effective technique to limit ANFs and improve nutrient digestibility in legumes [79]. Heating results in denaturation of the protein, an increase in surface area and exposure of cleavage sites that are otherwise inaccessible to protease enzymes [80]. Thus, a reduction in the concentration of ANFs, due to heat treatment is responsible for improved protein digestibility [81].

However, not all heat treatment is advantageous. Excessive or intensive heating may result in the degradation of heat sensitive amino acids and micronutrients and limit their bioavailability [30]. It may also lead to the formation of new products called neoantigens, which can elicit an allergic response. These neoantigens result from the Maillard reaction, by interaction of proteins with sugar residues upon heating [33]. Allergenic legume proteins elicit an allergenic response by surviving the acidic gastric conditions and action of digestive proteases. However, many are resistant to heat. Allergenic proteins in peanut are heat-resistant, while those in soya are partially heat-stable.

#### *6.3.2 Biological treatment*

During the germination of legume seeds, enzymes like amylase, protease, and lipase are activated to degrade starch, storage-protein and proteinaceous antinutritional factors. Germination is reported to suppress the amount of phytate, tannins, and trypsin inhibitors in different legume seeds [82], thus improving protein digestibility.

Fermentation is a traditional technique, where microorganisms facilitate enzymatic reactions that reduce the antinutrient content and thus increase the digestibility of plant proteins [83–85]. During this process, hard-to-digest proteins, like glycinin and β-conglycinin, of soyabean, are hydrolyzed to bioactive peptides. This results in improved solubility and hence higher protein digestibility of complex storage proteins [86]. This reduces the levels of undigested proteins that can cause food allergies [87]. Unfortunately, the microorganisms involved in the fermentation process can also

utilize amino acids and proteins, resulting in the loss of amino acids and proteins [85]. Therefore, due to lack of specificity and optimum conditions, which could lead to maximum protein digestibility with minimal loss of protein, the use of this technique remains unpredictable. Future food processing methods may need to incorporate techniques that reduce these antinutritional factors, and are economically feasible, for both the environment and customers.

#### *6.3.3 Enzymatic treatment*

The universal use of enzymes in food and feed processing is due to their unmatched specificity, operating under mild conditions of pH, temperature and pressure while displaying high activity, high turnover numbers and high biodegradability [88]. Thus, the application of enzymes is considered as a promising approach for plant protein modifications. Major groups of enzymes used in food applications are proteases, amylases, and lipases for the manipulation of proteins, starch, and lipids, respectively. Proteases can enhance protein digestibility by reducing the amount of trypsin inhibitors [38, 40, 41] and lectins. Phytase may also be applied in the industrial processing of soyabean to prepare certain foods for human consumption. Phytases have gained attention in human nutrition, especially to counteract zinc and iron deficiencies [89], by improving their bioavailabilities [90]. Saito et al. have developed a novel process for removal of the major soyabean storage proteins βconglycinin and glycinin, using phytase added to defatted soy milk at pH 6 with incubation at 40°C [91]. Phytic acid reduction by bioprocessing as a tool for improving the *in vitro* digestibility of fava bean flour has been demonstrated by Rosa-Sibakov et al. The improvement in protein digestibility was dose dependent and correlated to phytic acid content reduction, which explains the influence of enzymatic phytase treatment and LAB (lactic acid bacteria) fermentation on food digestibility, protein quality and protein solubility [92].

Food security is a global issue; hence increasing the nutritional value of food that is underutilized, will be an important part of the solution. Therefore, it will be interesting to explore the potential of enzymes in legume processing for human and animal health.

#### **6.4 Legumes in animal nutrition**

Legumes are used as a protein source in animal nutrition. Soyabean is the most important protein source in poultry and swine diets. Legumes are increasingly being used as a sustainable replacement for fish meals in aquafeed and pet diets. Globally, approximately 98 percent of soyabean meal is used as animal feed. Among the most significant ANFs in animal nutrition, are the trypsin inhibitors, found in raw soyabeans. By interfering with trypsin and chymotrypsin activity, they impair digestion in monogastric animals and some young ruminant animals [93]. Other young monogastric, such as swine, have also responded to soyabean meal, with reduced growth performance [94, 95]. Trypsin inhibitors have deleterious effects on animals. They result in stunted growth, reduced feed efficiency and pancreatic hypertrophy [93]. Lectins attach to mucosa cells damaging the intestinal wall and reducing the absorption of nutrients [63]. Glycinin and β-conglycinin are two allergenic soyabean proteins that are not digested easily. Glycinin damages intestinal morphology, causing intestinal atrophy and necrosis [94, 96, 97]. β-conglycinin causes a hypersensitive immune response and negatively affects the growth performance of animals [98, 99]. Other antinutritional factors like tannins cause decreased feed consumption in

#### *Digestibility of Proteins in Legumes DOI: http://dx.doi.org/10.5772/intechopen.110372*

animals, as they bind dietary protein and digestive enzymes to form complexes that are not readily digestible [100], reducing palatability and growth rate [101]. Higher concentrations of undigested protein, result in fermentation in the distal intestinal tract of poultry, and are attributed to the proliferation of pathogenic bacteria such as *Clostridium perfringens* [102–105], leading to diseases like coccidiosis and necrotic enteritis. Coccidiosis is the most frequently reported and economically important poultry-related disease worldwide [106].

#### *6.4.1 Use of enzymes in animal feed*

Monogastrics lack endogenous enzymes to break down soyabean anti-nutrients [107, 108]. Animal feed is not processed and hence ANFs that would normally be reduced in human nutrition by pre-processing, are not eliminated before they are consumed. Moreover heat treatment greatly reduces the nutritional value of the feed. Hence, an effective treatment to counteract these ill effects of ANFs, is the use of exogenous enzymes, added as feed additives to soyabean meal (SBM). Since trypsin inhibitors are proteins, they can be broken down and eliminated by the action of proteases. In an interesting study, protease inclusion in broiler diets, led to improved nutrient digestibility and upregulation of growth-related genes [109]. Enzyme supplementation of proteases (e.g., DigeGrain Pro 6), thus improves growth performance, by increasing protein digestibility. This results in better utilization of the protein content in the feed, leading to minimum wastage.

#### *6.4.2 Use of legumes as an alternative to fish meal*

Fish meal, due to its high protein content and palatability is the primary choice of feed in aquaculture [110, 111]. Small fishes like sardines and anchovies are extensively used for fishmeal, leading to overfishing and depletion of fish stocks in the oceans. In addition to not being a sustainable source of feed ingredient, fishmeal is associated with high cost, and hence alternative sources of protein and energy need to be investigated. Hence, recent research has focussed on the evaluation of plant proteins like soyabean meal, lupin meal, and various legumes (cowpea, green mung bean, rice bran) [112–115] as ingredients in feeds for aquatic animals. In diets where fishmeal was replaced by SBM (30%) in the feed of European seabass, optimum growth and feed utilization was maintained. No case of enteritis was observed in histological analysis, and nutritional status was similar as with fish meal [116]. Soy white flakes, a product obtained during soybean processing, was used to prepare aquafeed with suitable properties (lower water absorption and higher solubility indices, high durability, lower bulk density) [117]. Fermentation of SBM by a bacterial strain *Shewanella sp. MR-7*, prior to feeding, led to improved performance and alleviation of soy-related inflammation, caused due to ANFs [118]. In another study, the use of protease allowed slightly lower protein content to be used in the feed of Nile tilapia. Growth parameters, feed intake and feed conversion efficiency was unaffected. As an added benefit, water quality was improved due to lower ammonia and nitrite content [119].

Thus the replacement of fish meal with SBM, when coupled with protease treatment can avoid problems associated with trypsin inhibitors, use proteins efficiently and prevent excretion of undigested products that lead to contamination of water.

#### **7. Conclusion**

In 2022, the world population touched 8 billion and is estimated to reach 9.7 billion by 2050 [120]. An increase in legume production by �25% is needed to fulfill the protein demand of the world's population. Legumes have the additional advantage of having a low GHG footprint. However, efficient processes, both *in vitro* and *in vivo* must be employed in order to unlock the potential of legumes in nutrition. The use of enzymatic treatment, not only offers a greener alternative but also added health benefits. In spite of several health benefits, a considerable number of people are reluctant to include legumes in their daily diet. To increase the popularity of legumes in the diet, future research must focus on processes that improve the taste and texture of legume preparations, without stripping them of vital nutrition. The problem of low content of essential amino acids like methionine, can be circumvented by genetic engineering of legumes to increase the synthesis of amino acids like methionine, through metabolic engineering or through the engineering of legume proteins so that they contain higher concentrations of methionine.

The use of legumes coupled with enzymatic treatment in animal feed, will prevent unnecessary use of antibiotics and culling of animals due to disease, while improving their overall health, and result in economic benefits. Recently, the food systems have been threatened by the three C's, i.e., climate change, conflict, and Covid-19 pandemic [121]. The solution then lies, in maximizing the use of resources. Rather than following the mantra "more is better", optimum use of resources, is the need of the hour. Large production volatility and lesser profitability, relative to other crops are barriers to expanded legume use. A future transition to using legumes as a primary source of dietary protein may be made possible by increased consumer knowledge and investment in growing new varieties of legumes. Moreover, breeding of drought resistant varieties will enable legumes to be grown locally, and avoid dependence on supply chains. Overall, improving the protein digestibility of legumes will allow complete utilization of its nutritional components, prevent the wastage of food, and contribute to sustainability.

#### **Acknowledgements**

We thank Anil R. Narooka for his assistance in preparation of figures.

#### **Conflict of interest**

The authors declare no conflict of interest.

#### **Abbreviations**


*Digestibility of Proteins in Legumes DOI: http://dx.doi.org/10.5772/intechopen.110372*


### **Author details**

Stephanie A. Misquitta\*, Deepika N. Kshirsagar, Pooja R. Dange, Vikram G. Choudhari and Mukund M. Kabra Advanced Enzymes Technologies Ltd., Thane, Maharashtra, India

\*Address all correspondence to: stephanie@advancedenzymes.com

© 2023 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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#### **Chapter 8**

### Weed Management in Pulses: Overview and Prospects

*Rajan Sagar Chaudhary and Suman Dhakal*

#### **Abstract**

Pulses, the world's second-most consumed food, are an important source of food. They face several major challenges, including weed infestations, as a wide variety of weeds compete with them. Because of their competition with weeds, pulses can suffer a significant yield reduction. So as to alleviate such a menace, growers rely on different management tools, such as tillage, intercropping systems, and herbicides. Each method has been effective, albeit to varying degrees, in resolving the issue. Chemical herbicides, however, have served as double-edged swords over the past few decades due to their indiscriminate use. The repetitive use of the same herbicide or herbicides with the same mode of action confers resistance, thereby, leading to a serious impact on only nontargets. Therefore, it requires well-thought-out planning for a weed management strategy to maximize yields without creating environmental issues concomitantly. At the present, the integrated weed management approach has been accepted as the most reasonable tool for many farmers, which includes using preventive strategies, mechanical tools, crop rotation, intercropping, and herbicides with different modes of action, but cautiously. Modeling and robotics are the cutting-edge technologies that growers will be using for weed management in the coming days, thanks to the advent of such new innovation.

**Keywords:** weed flora, herbicides, weed resistance, Site-Specific Weed Management (SSWM), AI-driven machines

#### **1. Introduction**

The Fabaceae or Leguminosae family, also referred to as the legume, pea, or bean family, is the third-largest group of flowering plants, with more than 20,000 species [1]. The term "pulse" is limited to the annual legume crops that are specifically grown for dried and edible seeds. Chickpea, cowpea, pigeon pea, faba beans, lentils, and dry beans are some of the types of pulses [2]. Pulses are the second-most consumed food crop in the world, right behind cereal grains. They are a crucial source of food for the poor, particularly in developing and underdeveloped countries. Moreover, pulse-based products are in high demand among consumers around the world due to the significant nutritional value for the human diet they offer in terms of protein and mineral quality and bioavailability [3]. Incorporated into cropping systems, pulses increase the efficiency of both water and nutrient use, as they can fix atmospheric nitrogen into soils and allow companion crops to use stratified soil water, thereby contributing to sustainability in crop production [4].

A total of 89.8 million metric tons of pulses were produced worldwide in 2020, with India being the largest pulse producer [5]. A wide range of pulse crops are cultivated around the world, including chickpea (Cicer arietinum), pigeonpea (Cajanus cajan), mungbean (Vigna radiata), urdbean (Vigna mungo), cowpea (*Vigna unguiculata*), lentil (Lens culinaris *Medikus ssp. culinaris*), horse gram (Macrotyloma uniflorum), French bean (Phaseolus vulgaris), and lathyrus (Lathyrus sativus). There have been major challenges in increasing total pulse production to meet its global demand due to both biotic and abiotic stresses. Since pulses take so long to reach maturity, weeds often get a head start on the crops and end up smothering them. Furthermore, most pulses are grown in conjunction with nonlegume crops, and 84% of that area is grown under rain-fed conditions. For this reason, pulses are vulnerable to a wide range of biotic and abiotic stresses [6]. Weed infestation in crops accounts for the highest yield loss, i.e., 34%, compared to the losses associated with any pests, such as insects and pathogens, depending upon crops and weed's emergence time, density and nature [7, 8]. Weeds not only reduce crop yields but also impede other agricultural operations and serve as an alternative host for a wide variety of pests and diseases. It is vital to bring the weed density below the threshold level and maximize the crop yield and quality. In this review article, a specific focus is given on pulse's weed control choices for growers at the present and in the days to come.

#### **1.1 Major weed flora**

Various types of weeds have been reported to be associated with pulse crops, varying with the agro-ecological conditions and practices of crop management. However, the most abundant ones are presented in **Table 1**. The type of weed flora and the level of infestation in the field determine the extent to which crop growth and yield are affected. Reference [9] reported that non-grass types and sedges had a greater impact on the case of pigeonpea and sorghum intercropping than grass types. *Cyperus rotundus* L., more commonly known as nut grass, is a rhizospheric competitor with its network of underground tubers and is most prevalent during the summer and wetter months. Lambs quarter (*Chenopodium album*) is the most common and destructive weed in pulse crops. It thrives quickly and easily disseminates through seeds carried by the breeze. It not only competes with them for moisture but also spreads viral diseases [10]. Furthermore, WSSA [11] is in agreement with the fact that the aforementioned weed is the most prevalent weed in gardens.

A better understanding of environmental practices is by either increasing germination to kill seedlings or suppressing germination [12]. As a strategy for depleting weed seed banks, Gallandt [13] suggests influencing seed germination. In a similar way, understanding weed phenology could lead to more specific control methods by accurately estimating when and how weed competition affects crop yield [14]. It is important to note that most studies on the biology and ecology of weeds are based on a small number of populations. One region's population, however, may differ from another due to differences in management practices, rainfall, climate, soil type, etc. Consequently, it is necessary to include multiple populations in future studies.

#### **1.2 Crop loss**

The reduction in yield due to weeds can be up to 97% (**Table 2**); however, it varies with crops, weed intensity, crop management practices, and agro-climatic conditions.

#### *Weed Management in Pulses: Overview and Prospects DOI: http://dx.doi.org/10.5772/intechopen.110208*



#### **Table 1.**

*Significant weeds and their growing seasons associated with pulses.*


#### **Table 2.**

*Critical period and yield loss associated to major pulses.*

#### **2. Weed Management practices**

Understanding weed biology and ecology is essential for developing a sustainable weed management program. We still lack fundamental information on many important species, necessitating additional research. Nevertheless, there are many approaches that have been put into practice in farmers' fields with the intention of limiting the effects of weeds in effective and economically sound ways.

#### **2.1 Tillage**

It is one of the oldest preventive measures to avoid weed infestation. It uproots and leaves weeds exposed, taking control of weeds by burying their seeds deep enough to impede their germination and altering the soil-based growing environment. Taking an effective approach to controlling perennial weeds requires covering them deeply in the soil or drying them out by starving tactics [22]. There are several methods of tillage that are applicable to pulses. However, the efficacy of tillage varies with its methods, as we can observe in **Table 3**.

The use of moldboard plows prior to sowing had no discernible impact on chickpea yield, as demonstrated by Barzegar et al. [24]. Their findings state that, compared to moldboard, disk harrows were more effective against yield loss. Nighttime (photocontrol) tillage has been proven to be advantageous over weed management; nonetheless, due to its inconsistent results, questions have arisen about its effectiveness [25].

#### **2.2 Intercropping system**

Intercropping has been identified to be an effective approach in establishing agricultural systems and enabling sustainable agriculture goals. Hiltbrunner et al. [26] concluded that one of the greatest benefits of intercropping systems is weed control. Intercropping increases soil surface cover and plant diversity, two principles that control weeds better than monocropping. It has been shown in several studies that intercropping improves yields and eliminates weeds. Banik et al. [27] found that planting wheat and chickpeas together increases total yield productivity, makes better use of the land, and keeps weeds from growing. **Table 4** shows the efficiency of different inter-cropping systems in managing weeds in pulses [28].

Furthermore, according to Rai et al. [29], in pigeonpea + blackgram, and pigeonpea + greengram intercropping systems, weed suppression efficiency was found to be 69.6% and 69.4%, respectively, which were significantly higher than that of pigeonpea monocropping. This finding also concurs with the conclusion that intercropping is superior to monoculture for reducing weed damage to crops.


#### **Table 3.**

*Effect of different tillage practices for weed management in mung bean.*


#### **Table 4.**

*Weed-Smothering Efficiency (WSP) of different pulse-based intercropping systems.*

#### **2.3 Herbicides**

Herbicides are a significant piece of agricultural technology that has contributed, at least in part, to the agricultural revolution that has occurred in recent decades and to the accompanying rise in the amount of food that has been produced. Herbicides, a major component of pesticides, are one of the external factors and a group of synthetic chemical and biochemicals used to suppress or kill unwanted vegetation [30]. Increasing labor shortages in agriculture, coupled with the need to maximize crop productivity to meet the needs of a growing global population, have led to the widespread use of herbicides for weed control, leading to their adoption as one of agriculture's most popular weed control strategies [31]. An author [32] added that reducing soil erosion resulting from tilling is another advantage of the approach. Nevertheless, maintaining the efficiency of existing weed control options necessitates that herbicide use practices and recommendations be regularly updated and revised to keep up with the ever-changing weed ecology (**Table 5**).

It is imperative that herbicides be applied only at the time specified on the label and in accordance with the recommended intervals between the time of treatment and the time of planting or harvesting the crops. Whenever there is a possibility of rain within 2–4 hours of application, it is best to avoid herbicide applications. The use of herbicides requires a great deal of caution from us [34]. Several countries have restricted the use of some herbicides because of the health risks they pose. Paraquat, for example, is restricted in some countries due to its acute toxicity and association with Parkinson's disease. That means, the aforementioned chemical can only be applied by certified applicators for the purposes of scientific research and observation.

#### **2.4 Integrated Weed management**

Herbicidal technology has faced significant shifts in its effectiveness in agricultural systems, which can, in some instances, result in the failure of weed control applications. This is primarily attributable to the perpetuating development of weed tolerance and resistance, as well as the development of the herbicide industry and its associated limitations. We have some data on cases of herbicide-associated resistance as expressed in **Figures 1** and **2** [35].


**lb a.i.** *= Pounds active ingredient,* **EPP** *= Early Preplant,* **PPI** *= Preplant Incorporated,* **PRE** *= Preemergence,*  **EPOST** *= Early Postemergence,* **POST** *= Postemergence*

*Sites of action (groups):* **1** *= ACCase Inhibitor,* **2** *= ALS Inhibitor,* **3** *= Microtuble Inhibitor,* **8** *= Lipid Synthesis Inhibitor,*  **9** *= EPSP Inhibitor,* **14** *= Cell Membrane Disruptor (PPO Inhibitor),* **15** *= Seedling Shoot Inhibitor,* **22** *= Cell Membrane Disruptor (PSI Inhibitor)\*indicates Restricted Use Herbicide.*

**Table 5.**

*Environmental Protection Agency (EPA)-approved herbicides recommended for pulse crops by Johnson et al. [33] based on research conducted at the South Dakota Agricultural Experiment Station and other studies.*

**Figure 1.**

*A global increase in unique resistant cases at different years.*

**Figure 2.**

*The top 10 herbicides, along with the number of associated resistant species. Source: [35].*

The widespread use of herbicides that primarily have the same or a similar mode of action is hamstrung by the emerging risks of environmental hazards, the introduction of herbicide resistance in various biotypes of weeds, and the nonselectivity and narrow spectrum of herbicides, all of which contribute to limiting the scope of herbicide use. To develop an effective and sustainable weed management strategy, it is essential to first comprehend the selection pressure of an organism. Selection pressure is an outcome of virtually anything as long as the survival and reproductive pattern of a species are influenced, provided that it acts in a relatively consistent manner over and over again [36]. It is worth pointing out that this is the case with herbicide resistance. The repeated use of the same active ingredient or of the same mode of action eliminates susceptible weeds from a population, leaving only the resistant ones, which become dominant species over time; the development of herbicide resistance can be considered an evolutionary process [37].

The development of herbicide-resistant weeds is associated with several factors, including selection pressure, the weed's genetic variability, inheritance patterns, gene flow, herbicides' nature, agro-ecosystem factors, and others [38]. In light of this, it is not always possible to come up with a single management strategy for controlling and preventing the spread of herbicide-resistant weeds; instead, an integrated weed management (IWM) approach is required.

Integrated weed management (IWM) strategies for managing resistant weeds:


#### **2.5 Modeling and robotics for SSWM**

Site-specific weed management (SSWM) is a state-of-the-art weed management approach that allows optimization of weed treatment for each unique agronomical site, with precise and continuous monitoring and mapping of weed infestations, which has been proven highly efficient and environmentally safe for control of weed populations [39, 40].

This system relies on multidisciplinary technologies such as image sensing techniques (multiple-dimensional cameras and multispectral imaging), GPS, remote sensors, artificial intelligence (AI), and machine learning algorithms for discerning a specific weed and its population, thereby allowing unmanned vehicles for weed management via targeted spraying, automated hoeing, or other techniques. In conjunction with the new sensor technologies, decision support systems (DSS) can help farmers apply weed control treatments at the right time, with the right intensity, and in the right places [41].

#### *2.5.1 Drones*

Precision agriculture has adopted unmanned aerial vehicles (UAVs), primarily drones, as a common tool [42, 43]. Due to their affordability, user-friendliness, and adaptability, UAVs are frequently the preferred option for rapid and accurate in situ remote sensing or survey operations. Despite their adaptability, these systems can serve a variety of purposes depending on the sensors they carry. UAVs, as one of the most effective tools for weed mapping, are critical for SSWM. The workflow consists of three significant phases: 1) collection of field images, via sensor cameras, 2) image processing, which recognizes weeds and pinpoints their whereabouts and patches via deep neural networks or other AI techniques, 3) training-specific algorithms to eliminate the targeted weeds with herbicide spraying by drones or mechanically with unmanned terrestrial vehicles (UTVs). There are three types of sensors attached to UAVs, depending on the payload and weed/crop recognition system and other purposes: 1) RGB (Red, Green, and Blue) or VIS (visible) sensors, 2) multispectral sensors, and 3) hyperspectral sensors. With up to 80% precision, hyperspectral sensors can differentiate between glyphosate-resistant and glyphosatesusceptible Kochia biotypes [44]. And the accuracy rate is 96% for *Amaranthus palmeri* in real field bases [45]. A novel alternative to UAVs could be laser-equipped robots.

#### *2.5.2 Autonomous laser weeding*

Andreasen et al. [46] highlighted that Autonomous Laser Weeding is a cuttingedge technique for weed management that is a prototype, not yet widely used or sold commercially. Artificial intelligence and deep learning are being deployed to precisely locate and distinguish weeds [47, 48] and burn the meristems of the targets with laser beams released by robotic actuators for real-time weed control. Beam quality is a crucial parameter for laser applications, particularly weeding, as it determines the maximum power density that can be achieved. At least 54 joules of laser energy per plant were required to cause lethal damage to each treated plant with a 95% probability. Lethal damages are contingent upon weed species, growth stage, laser spot position and area, and laser energy (J) applied [49–51]. Papadopoulos [52] reported that LaserWeeder, a product of Carbon Robotics, is an autonomous laser robot that has the capacity of eliminating 200,000 weeds per hour by incinerating active ones, with a performance increase of 100 percent over the system's first version.

Need-based spatial spraying minimizes selection pressure on herbicide-resistant weeds and herbicide diffusion with only minimal interference with nontargeted plants. Importantly, laser robots offer substantially less interference with biodiversity and the environment, achieving the goal. Due to their lighter weight, UTVs perform site-specific weeding with acceptable soil impacts, creating a more favorable environment for crop growth. There have been positive impacts on ecological and agro-economic aspects, as depicted in **Figure 3**. It is possible for these robotic devices to replace organic growers' manual weeding practices. However, it can be challenging or may take some time, particularly for developing countries, to introduce and adopt such a novel approach.

#### **3. Conclusion**

To overcome the weed infestation, farmers have been using different tools and methods, and among them, the herbicide-use approach is widely adopted due to

**Figure 3.** *Drone-based site-specific weed management (SSWM) and its impact on the Agri-economy and ecology. Source: [53].*

its ease of use and labor shortage. Long-term weed management is unlikely to be achieved through the use of a single method of weed control, since this approach often leads to the development of weed resistance. This is not only the case with herbicides; even repetitive hand hoeing over and over may force weeds to adapt to such a stressed environment and build resistance/tolerance. Over the past few years, herbicide resistance and resistance management have been of great interest to weed scientists. Site-specific weed management (SSWM) is likely to improve the sustainability of weed management by treating only the weed species community, using image analysis and machine learning techniques. Further studies are crucial and in high demand to make this novel approach applicable in real agricultural situations.

#### **Author details**

Rajan Sagar Chaudhary1 \* and Suman Dhakal2

1 Agroforestry Polytechnic Institute, Lumbini Province, Nepal

2 Agriculture and Forestry University (AFU), Rampur, Chitwan, Nepal

\*Address all correspondence to: rajandang031@gmail.com

© 2023 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

*Weed Management in Pulses: Overview and Prospects DOI: http://dx.doi.org/10.5772/intechopen.110208*

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[22] Jorgensen MH. The effect of tillage on the weed control: An adaptive approach. In: Radhakrisnan R, editor. Biological Approaches for Controlling Weeds. London, UK: InTech; 2018. pp. 17-25. DOI: 10.5772/intechopen.76704

[23] Singh PK, Singh SK, Shukla MK, Singh C, Kumari M, Singh R, et al. Effect of different tillage practice, herbicide and rhizobium on weed, yield and economics of mung bean (Vigna radiata L.). Internationl Journal of Multidisciplinary Research and Development. 2016;**3**(7):257-259

[24] Barzegar AR, Asoodar MA, Khadish A, Hashemi AM, Herbert SJ. Soil physical characteristics and chickpea yield responses to tillage treatments. Soil and Tillage Research. 2003;**71**(1):49-57

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[26] Hiltbrunner J, Liedgens M, Bloch L, Stamp P, Streit B. Legume cover crops as living mulches for winter wheat: Components of biomass and the control of weeds: Semantic scholar [internet]. European Journal of Agronomy. 1970 [cited 2023Jan7]. Available from: https:// www.semanticscholar.org/paper/Legumecover-crops-as-living-mulches-forwinter-of-Hiltbrunner-Liedgens/60988b6 ccdf0ed4db95c05b69ae906fb35955b4b

[27] Banik P, Midya A, Sarkar BK, Ghose SS. Wheat and chickpea intercropping systems in an additive series experiment: Advantages and weed smothering. European Journal of agronomy. 2006;**24**(4):325-332

[28] Ali M. Weed suppressing ability and productivity of short duration legumes intercroppped with pigeonpea under rainfed conditions. International Journal of Pest Management. 1 Jan 1988;**34**(4):384-387

[29] Rai CL, Tiwari RK, Sirothia P, Pandey S. Intercropping and weed management effects on weed dynamics, productivity and economics of pigeonpea. Weed Science. 2016;**48**(1):44-47. DOI: 10.5958/0974-8164.2016.00010.1

[30] Qasem JR. Herbicide Resistant Weeds: The Technology and Weed Management. In: Price AJ, Kelton JA, editors. Herbicides–Current Research and Case Studies in Use [Internet]. London: IntechOpen; 2013 [cited 2023 Jan 14]. Available from: https:// www.intechopen.com/chapters/44981 DOI: 10.5772/56036

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[32] Pacanoski Z. Herbicide use: Benefits for society as a vvhole-A review. Pakistan Journal of Weed Science and Research. 2007;**13**(1-2):135-147

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[34] Dhaker DL, Maurya S, Singh K. Chemical Weed Management increasing herbicide efficiency. Agriculture and Environment. 2021;**2**(10):31- 32. Available from: https://www. researchgate.net/publication/357327269\_ Chemical\_Weed\_Management\_ Increasing\_Herbicide\_Efficiency

[35] Heap I. International Herbicide-Resistant Weed Database [Internet]. Weedscience.org. 2021 [cited 2022Dec17]. Available from: http://www. weedscience.org/Pages/Graphs.aspx

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[37] Sosnoskie C. Selective forces that act on weeds [Internet]. Progressive Crop Consultant. 2019 [cited 2023Jan7]. Available from: https:// progressivecrop.com/2019/09/ selective-forces-that-act-on-weeds/

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[43] Daponte P, De Vito L, Glielmo L, Iannelli L, Liuzza D, Picariello F, et al. A review on the use of drones for precision agriculture. In: IOP Conference Series: Earth and Environmental Science. Vol. 275, No. 1. Bristol, UK: IOP Publishing; 2019. p. 012022

[44] Scherrer B, Sheppard J, Jha P, Shaw JA. Hyperspectral imaging and neural networks to classify herbicideresistant weeds. Journal of Applied Remote Sensing. 2019;**13**(4):044516

[45] Reddy KN, Huang Y, Lee MA, Nandula VK, Fletcher RS, Thomson SJ, et al. Glyphosate-resistant and glyphosatesusceptible palmer amaranth (Amaranthus palmeri S. wats.): Hyperspectral reflectance properties of plants and potential for classification. Pest Management Science. 2014;**70**(12):1910-1917

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#### **Chapter 9**

## Future Use Prospects of Legumes through Improvement and the Challenges Faced

*Briggx Xavier*

#### **Abstract**

Legumes are important crops, being one of the most protein containing species of grain plants from their seeds which are used as food among other uses of the crop such as Nitrogen fixation (in most), which helps maintain soil nutrition at bay. The uses extend to key ingredients in livestock feeds manufacture even for marine life diets. Their roots go deep into the soil to find water and in the process hold soil particles together aiding in soil erosion control. However, low performance and production levels have been recorded over the years with Africa, for example, contributing only 10% of the entire world legume production per year. This is attributed to little breeding programs being conducted on the legume plants among less improvements aiding in the plants' performance and production for sustainability. This book chapter therefore seeks to outline in depth some of the future prospects of legume plants species in relation to improvements that should be done on the crop such as breeding programs to sustain diverse functions, among which, increasing food security. The improvements not only aim at helping humanity, but rather the environment in general including marine life.

**Keywords:** nitrogen fixation, soil erosion, marine life, sustainability, food security

#### **1. Introduction**

The leguminous family of plants is the largest pods-producing flowering plants family with over 18,000 different species classified into 650 generic classes [1], under the 1/1/12th of all known flowering plants on the planet earth. Not all legumes fix atmospheric nitrogen. Among the *Leguminosae* subfamily, the *Fabaceae* species are recognized as those with the primary agricultural role in the group. Herbaceous and woody legume plant types from the *Fabaceae* species have been used for pastures, animal feeds, erosion control, agro-forestry purposes and as sources of green manure traditionally. Above the uses, they also yield important industrial substances such as tannin, resin for making gums and glues, synthetic dyes, perfumes, insecticides and bio-fuels. Some of these leguminous family valuable food crops include, peas, common beans, peanuts and soybean, which produce high protein grains for human consumption, making an important constituent in their diet. Of all the plants that man used as food, only the grasses are more stable as compared to the legumes [2]. Despite considerable resources being directed towards the development of grasses such as rice, maize and wheat, only peanuts and soybeans within the leguminous family have been thoroughly given priority on the same. The world's increasing population needs adequate food to feed its citizens so as to prevent common malnutrition problems, which is prospected to be greatly contributed by dietary legumes in order to achieve food security in our nations.

Through improvements that aim in increasing the performance and yields of legumes, these plants are super contributors to the economy to ensure food security among nations in the word. Breeding programs such as gene mapping to identify and isolate traits aid in the selection and isolation of genes of interest from plants which are improved and modified then used in legumes to boost the performance [3]. Other technologies include breeding to suit performance roles such as adaptability to environments, for example deep roots in search for water. Legume produces can be improved for uses in the food industry for humanity, in feed industries such as in ruminants dies replacements and in industries and in the pharmaceutical industries in the manufacture of drugs.

Besides the improvements, there are many breeding technologies which are aimed at improving performance and yield currently. An example is the breeding for lodging resistance which reduces yield losses especially during heavy rainfall seasons by avoiding plant bends which promote rotting once the pods come into contact with moisture. Breeding is also done to increase the general yields of the plant by increasing the number of produces per plant in many agricultural crops. Breeding is done to reduce grain shattering in legumes especially during harvesting stage. This is by preventing the chances of the pods to open which leads to losses through spillage [4, 5]. All these are some of the many examples which are believed to form the basis for this chapter. This is because in order for improvements to occur, much grains must be produced, and of high quality as the grains are the requirements in implementation of most of the improvement prospects.

As agronomists, scientists and researchers, our main perspective is to think of legumes in the primary role of aiding in nitrogen fixation to otherwise deficient soils. Despite, other scientists outside the "agriculture" field view the crop for diverse benefits and uses, such as use as a vital source of food and forage, use in rotation with other crops to improve yields and also as a forest commodity essential for providing firewood traditionally or shelter. However, some scientists from the medical field now view the crops as a source of pharmaceutical ingredient in the manufacture of major drugs for hospital use in a range of maladies. This role should not be under looked when we display that legumes have been a major component of traditional medicine among communities for centuries. Despite the purpose you intend to grow the crop for, its symbiotic role, that is, the association between the nitrogen fixing bacteria in the root nodules (rhizobia) and the plants, play a significant role in agriculture production sector by reducing ca. 100 million metric tons of atmospheric nitrogen into ammonia [6], thus saving the world about US\$30 billion on Nitrogen fertilizer every year. Following photosynthesis process in plants, we might consider viewing Biological Nitrogen Fixation (BNF) by legumes as the next most important essential natural occurring biological process in plants. There is still a challenge on the realization of this process as many developing and developed countries all over the world have not fully embraced Biological Nitrogen Fixation but instead rely upon nitrogen fertilizer to drive agricultural productivity. This lack of adoption of the process is majorly attributed to many factors ranging from little knowledge and expertise in both the manufacture of inoculants and in the growing of inoculated legumes with

#### *Future Use Prospects of Legumes through Improvement and the Challenges Faced DOI: http://dx.doi.org/10.5772/intechopen.109428*

rhizobia. Some governments in many countries across the world with advanced economies also are viewed to participate in this by providing subsidies which mitigate against the use of Biological Nitrogen Fixation (BNF). Unfortunately, with the fossil fuel prices hiking, small economies will most likely be faced with either food shortages, high food costs or inflated fertilizer nitrogen prizes. Many developing countries such as those in South Eastern parts of Asian continent rely upon buying of urea (a nitrogenous fertilizer) for rice production [7]. This is a problem that needs to be addressed as soon as possible due to the current forecast that food production will have to double by the next 10 years so as to feed and sustain the expanding population. This can only be avoided with employment of Biological Nitrogen Fixation (BNF) inputs.

Apart from direct benefits of artificial nitrogen fixation from legumes, they also provide additional importance in aiding in weeds, pests and pathogens control, improving soil fertility when the plants die and form organic manure and ensuring stability from rotation in different and diverse cropping systems with different species of crops. Taking a look at a country like the United States of America (USA) alone for example, alfalfa, *Medicage sativa,* is currently estimated to be the third most valuable crop worth up to \$7 billion annually [8]. However, intense pressure from biological, environmental, human health as well as economic sectors dictate that the legumes suite and their use in the modern civilization to be dynamic rather than fixed. This chapter outlines how legumes can be developed, more so rhizobia, for future diverse uses not only in agriculture but outside fields as well.

#### **2. Legumes future breeding improvement prospects**

#### **2.1 Legumes use in pharmaceutical industry to solve health problems**

The strong consumer-driven trend for natural products in the world has pushed for shift to natural active ingredients in medicines manufacture. Of the active ingredients prescribed in pharmaceuticals, 25% are flowering plants-derived, expected to increase to about 30% in the next 10 years to come. On this, of the antineoplastic drugs that are prescribed in the Western countries and in Japan, 54% are natural occurring products or their analogs [9]. Many consumers in the world aim at natural drugs, believing that they are safer that synthetics. This has also pushed many, more so in African countries, to go the herbal medicine direction rather than buying drugs from chemists and pharmacies. The current global market for natural pharmaceutical products is estimated at US\$30 billion growing at an increasing rate of 6% per annum [10]. Herbs (which also includes many legumes), possessing anti-cancer or penile potency properties are the main focus of smuggling into the European, Japan and the USA markets. Advances in analytical chemical techniques in plants, such as High-Performance Liquid Chromatography (HPLC), Mass Spectroscopy (MS) and Nuclear Magnetic Resonance (NMR) have allowed the rapid identification of proteins in plant cells that are responsible for increasing the legumes value, particularly in regards to the pharmaceutical industry. References proposed that legume plants species combine essential genomic materials with biochemistry thus forming a compound which is of acute relevance to human health.

Non-traditional benefits of legumes in human diets have been emphasized also in the recent years commonly. These benefits include, alfalfa sprouts and soybeans use as a source of phytoestrogens which aims at reducing menopause symptoms majorly

in women and also aiding in maintaining bones health. In the Chinese medicine for example, one of the old-dating known useful plants is the licorice, (*Glycyrrhiza glabra,* a popular legume herb known for its anti-ulcer and anti-inflammatory properties. Legumes also contain useful chemical compounds in their protein-DNA that are essential for their ant-diabetic, anti-allergenic as well as anti-inflammatory properties [11]. Plant Genetic Resource Conservation unit (PGRC) within the United States Department of Agriculture (USAID) is currently conserving 17 different legumes species containing essential phytochemical properties with positive human health impact. Some of these plant legume species include the butterfly pea, *Clitoria ternatea l.,* known for its anti-fungal properties, hyacinth bean, *Lablab purpureus.,* known for its anti-hypertensive properties and kudzu, *Pueraria montana* var. *Lobata willd*, known to containing isoflavone daidzein properties essential as an anti-inflammatory, anti-microbial and cancer preventive treatments. The five pyran isoflavones isolated from a *Fabaceae* family species rootstock, *Eriosema kraussianum,* contains 75% properties of Viagra which increases blood flow in rats' penile tissue as the active ingredient. *Trigonella foenum-graecum l.* plant popularly known in the Indian medicine for increasing lactation in women [12], also contains numerous chemical properties of interest in the modern pharmaceutical sector, for example, diosgenin and coumarin.

Legumes also contain phytoestrogens with great biological activities currently being applied to humans for menopause and osteoporosis treatments. These phytoestrogens are plant-derives chemicals, so named due to their possession of both estrogenic and anti-estrogenic traits, although much less effective than the genetically human produced estrogens. Isoflavonoids are one major phytoestrogen class that includes genistein, daidzein and equol compounds. They are also among the most extensively classes of phytoestrogens to be researched. Isoflavonoids are the most particular prevalent classes in the *Fabaceae* sub-family of leguminous plants the most studied being the ones from soybeans and red clover, *Trifolium pratense l.,* species. The isoflavonoids extracted from red clover and soybeans are now being used as alternative compounds in the Hormonal Replacement Therapies (HRT) for the treatment of the menopause-related disorders [13].

Soybeans are the main dietary source of food of the two isoflavonoids, genistein and daidzein, in humans, present in their glycoside forms. A huge consumption of foods containing high soy-based products may result in high plasms levels, high urine and prostate phytoestrogen fluid concentrates. Epidemiological studies on the other hand suggests that women in Asian countries with a high phytoestrogens dietary intakes have a decreased breast cancer risk rates and also a lower menopauseincidence symptoms. As well, the study still suggests that men consuming high-soy product traditional foods have a lower prostate cancer incidences especially Asian men as compared to European and American men. Although these claims may not provide sufficient evidence and still awaits further study, numerous in vitro studies support a role of genistein in inhibition of the growth of a number of cancers [14].

Laboratories in vitro studies have produces alcohol extracts from a wide range of legume leaves and stem tissues that aid in in inhibiting the growth of MCF7 breast and LNCaP prostate cancer cells [15]. Soybean isoflavonoids is also suspected to have a role in the maintaining of healthy brain tissues and also in the treatment of ageassociated cognitive declines such as Alzheimer's disease, loss of memory episodes, and improving the general cognitive functions in the brain.

Many of these mentioned secondary plant compounds are mostly found in small quantities and tend to be synthesized in specialized cells in the plants or at specific growth stages. This makes their identification, extraction, separation and purification processes more challenging. Nevertheless, equipment has been invented and now currently available, which are aided to speed up the extraction of the useful legume compounds for use in human medicine improvements in the pharmaceutical industry.

#### **2.2 Legumes use in food industry**

Due to most of the underutilized legume plants' high nutritional properties, some essential proteins can be extracted from the plants and used in the food industries in the manufacture of various products. For example, edible products such as cooking oil can be extracted from soybean and the African yam bean. This is due to their high lipid contents [4]. These lipids used in the manufacture of the cooking oils is obtained from the seed grains, which are processed to produce the final product "oil".

Underutilized legumes can also be processed into flour. This will not only extend the shelf life, but also diversify food by increasing the options for the legume produce use. The process is done after the grains have recorded a reduced moisture content of 4% or less [5]. After that, the grains are taken to the grinding machine after which processed into flour. This flour can now be stored for up to six months depending on the storage conditions. On another option, the flour can be used in preparation of foods such as the famous "ugali" in many African countries. The flour can also be used in a combination with other grain flours such as maize flour, millet flour and sorghum flour in making of porridge which is a good example of breakfast foods for use with either bread or other breakfast food choices.

The processed flour can be used in the baking industries [16]. Here, the flour is processed into legume breads. Some of these breads can be made from undermined legume crops such as soybean. This will very much aid in diversifying food uses too not only consuming the grains directly for lunch dishes, but through processing, legume-bread can also be made which is a good breakfast choice and even for export to other countries.

#### **2.3 Legumes use for ruminants benefits**

When it comes to the emergence of herbicides resistance in weed control, development and implementation of chemical control method for gastrointestinal parasites in grazing animals is an equilibrium between seeking of efficiency and avoiding the resistance development. Nematodes in sheep such as *Osterstagia circumcincta, Haemonchus contortus and Trichostrongylus spp.* are a major cause of livestock mortalities and reduced production, and further widespread resistance to anti-helminthics treatment effective control. However, there is sufficient evidence that plant natural occurring tannins in majority of forage legumes can reduce worm infestation issues in grazing animals, hence reducing the requirement for deworming. This in turn provides a new weapon in the management of anti-helminthic parasites resistance. The potential anti-helminthic tannin or CTs containing properties are described as proanthrocyanidins, phenolic compounds present in varying concentrates in wide range of leguminous forage plants. CTs form an important part of the plants defense against bacterial and insect predation and also against invasion into grazing vegetation for herbivores. The CTs may also have a positive impact on ruminant nutrition by increasing the efficiency of utilization of proteins. Through the reversible of binding to plant proteins, CTs are postulated to interfere with the protease activities produced by the rumen micro-organisms thus reducing the protein degradation process in the rumen and in return allowing a larger portion of protein to reach the ileum [17].

However, despite the discussed benefits of leguminous CT plants in increasing the wool growth more so in sheep, milk production in mostly dairy livestock, increasing reproductive rates and aiding in bloat control, high tannin concentrations can also reduce the voluntary feed intake rates in ruminants resulting to reduced animal performance. All these effects of CTs towards ruminants vary evidently according to the nature, concentration and the structure of different compounds and potential anti-helminthic properties.

Positive benefits of various leguminous CT forage plants in reducing worm infestation challenges in sheep have been identified in numerous studies. For example, in feed experiment trials, significant reduction in worm infestation levels have occurred in sheep grazing in tannin containing forage plants such as sulla, *Hedysarum coronarium,* lotus, *Lotus pedunculatus,* birdsfoot, trefoil, *L. corniculatus* and chicory, *Cichorium intybus.* pen studies conducted with tannin extracts also indicate that there is a large decrease in sheep-worm egg count and also a lowered worm infestation rate. In goats, pen studies as well also indicate a decreased *Haemonchus contortus* and their significant anti-parasitic effects with *Sericia lespedeza* forages in all pens in the trials. in a general view, the worms egg counts are lowered within a week post the introduction to CT-containing pasture legumes or rotations [18], with much decreases in total worm numbers up to 30–35% in relation to introduction to non-CT legume groups.

#### **2.4 Legumes use in aquaculture and marine feeds**

Aquiculture sector over the years has expanded very quickly that it currently provides over 30% of the world`s global fishery products to industrial ones. Although marine-based ingredients such as fishmeal and fish oil are manufactured in industries and remain many people's preferrable protein and oil sources from aquaculture products, it is projected that by the next 10 years or so, 50% of the world's fish catch will most likely be directed towards legume feeds [19]. The current and modern intensive aquaculture practices is therefore viewed as a net fish user rather than producer which is very much undesirable and should not be the trend. Almost much of the soybean meal extracts have already been approved and verified for use as alternative protein and energy source by the aquaculture industry sector. On top of that, sweet lupin, *L. angustifolius,* and other legume grain extracts are currently underway in evaluation appearing to be current substitutes of fish manufactured feed products. Can other legumes specifically those that can be produced intensively satisfy the increasing protein and energy demand in the aquaculture industry at large?

Fish do not require carbohydrates in their diets and their presence in grain legumes can reduce fishmeal digestibility produced from the grain legumes and cause huge decrease in protein retention in fish yet they require S-rich amino acid proteins and fatty acid or lipid oils in their diets. Even though these compounds are provided by legumes in different ratios, anti-nutritional factors similar to the ones previously discussed for humans and other monogastric animals also affect fish [20]. Most notably are the saponins, protein inhibitors, oligosaccharides and high cellular or fiber content. All these and other potential tainting molecules, for example, coumarins cannot be assumed in the formulation of fish diets, however, extracting them from legume grains requires expensive procedures or an extensive breeding program approaches to achieve.

One of the important roles of fish in human health is related to the long chain omega-3 to omega-6 oil ratios with more than 18-carbon atoms on a straight chain in marine products. Two issues of importance arise from here in relation to oil from

#### *Future Use Prospects of Legumes through Improvement and the Challenges Faced DOI: http://dx.doi.org/10.5772/intechopen.109428*

legume plants. First, legumes produce predominantly C18 oils rather than C20 and C22 oils from fish proven to have beneficial importance to human health. Fish from fresh waters can synthesize C22 fats from C18 precursors as compared to marine fish, mainly cold-water ones, which are much less able to do so. Secondly, the omega-3 omega-6 ratio considerably between leguminous plants and fishmeal, with a much difference of up to more than 100 folds [21]. For more improved human health, a high omega-3-omega-6 ratio is essential, and if lower oil levels are ultimately reflected in fatty acid content of aquaculture end products, the legume-fed fish value in human diets needs to be supplemented.

Nevertheless, dietary substitution of fishmeal in aquaculture fish feed diets containing high protein grains is attractive, particularly those containing omega-3 and omega-6 oil fats rates.

#### **2.5 Perennial legume improvement for increase water access from deeper roots**

Another prospect for the future use of legumes is in the provision of a hydrological stable to low input agriculture ecosystems which are pocket friendly. When left undisturbed, grass fields and ecosystem ranges often contain different several annual and perennial plants species mix including herbs, shrubs, trees, grass and also legume family species as well. This unique mix of natural biological plants in the temperate climates contributes to the hydrological stability in the ground and underground water systems of the most part of the world's land mass, with the species with deeper rooting systems translocating water from deeper depths during the drier periods of summer and autumns. In South Australia for example, the natural perennial mixes of shrubs, trees, annual grasses and herbs was violently disturbed and destroyed with the people's ruthless clearing of 25 million hectares for agriculture in the nineteenth and twentieth centuries. In return, larger areas in the region have since been seriously affected by a combination of high salinity levels and waterlogging as a result of the rising water tables due to decrease in water utilization as a result of deforestation and vegetation clearing practices. Currently, in South Australia where the example was picked, the total affected unit land area is estimated to exceed 5 million hectares [22]. On this, the largest scale land use is observed to be under pasture for livestock use which is then the greatest potential for the disaster cause. Farming systems therefore, not only in Southern Australia but all the regions faced with the same challenge across the globe needs to be resolved by employing redesigning strategies in the current Century so as to restore the water use pattern of native flora with the main aim being the discovery of plants and improvements for both economical and hydrological benefits, including legumes.

Perennial legumes are speculated to play a significant role in the redesignation agriculture. Many studies estimate *M. sativa* to being adopted to 96% of most soil types in the entire world even where the soils are fertile or alkaline making the suitable for adaptability. Much of the perennial legume species that are found in the rangelands of the Mediterranean basin surroundings can be elevated to welcome *M. sativa* in the setting more so where improvements are required. This will not only help in water utilization but the diverse benefits which come with legumes as well as discussed previously. However, when it comes to the acidic and more coarse-textured soils, which represents approximately 30% of most agricultural lands in many regions, a different suite of perennial legumes and rhizobia to those exploited in agriculture will need to be developed as a result of breeding programs for adaptability and suitability [23]. This is because none of the current commercial legume species all over the world is adapted to the combination of edaphic aridity stresses, infertility nor acidity stresses in any region. By the development and improvement breeding programs as well, this will provide a major opportunity for the development of legumes by many upcoming scientists and breeders in the near future to serve for purposes.

### **3. Challenges faced in breeding improvement prospects for legumes**

#### **3.1 Health concerns**

On the breeding of new legumes with high nutritional quality for monogastric or human consumption, many anti-nutritional and health factors have to be considered, more so ethical issues and points of concerns from the wild legume types and varieties. These concerns include non-protein amino acids, alkaloids, glycosides, tannins, saponins and protease inhibitors from wild legumes, which require further testing as they are ethically not yet viewed as safe healthwise. Even though some societies have found a way to deal with these anti-nutritional factors through processing techniques such as high heat boiling for long duration, soaking, leaching, fermentation and dehulling, this is often not a common practice in today's large economies in both developing and developed worlds. Even though some of the anti-nutritional properties are driven by single genes, it will not be an easy task to isolate and combine all the necessary genes required for the domestication traits among species into a single new superior species that will in return displace the contemporary grain legumes suite in farming systems and markets across the world. The most recent example of the domestication was seen in *L. angustifolius* in the 1970s, following its adoption on acid sandy infertile soils in Western Australia [24]. This advancement in the crop was faced with several highlighted difficulties into the legume market by the novel legumes due to the health concern suspicion among the people thus making its utilization difficult. Despite *L. angustifolius* acquiring an important ground from its rotation with many cereal crops on more than 750,000 hectares of land annually, the price paid by its seeds constrained include;


Lupin is considered primarily as an animal feed in many marketplaces whereas traditional other common grain legumes are cultivated for human consumption and fetch higher market prices, for example Cicer, Vicia and Lens legumes. However, despite this negative faced by the crops, lupins remain popular across many farming systems due to their ability to fix over 100 units of nitrogen per hectare, while still providing many additional rotational benefits associated with legumes in coexistence with other crop species in the field [26].

#### **3.2 Social and technical adoption challenges**

There exists other many social and technical barriers to the legume adoption as well in the current world. For example, farming systems are distorted by high price subsidization more often, ignoring the direct and associated benefits of legumescultivation especially in the rural regions. Also, much direct financial support to farmers is needed to ensure arable lands remain occupied and busy but eliminating the incentive to develop efficient farming systems which are based upon Biologicallyfixed nitrogen. The recognition of the environmental pollution in manufacturing and utilization of nitrogen fertilizers should be considered as it slowly increases embracing of Biological Nitrogen Fixation (BNF) in many regions across the world. In other circumstances as a result, investment in legumes is not much often realized for long recurrent growing seasons and thus, the legumes growing of the crop that generates higher quicker instant cash flow is significantly instead lost. When it comes to communally owned lands, it often even makes it more difficult to manage the long-term practice of improved forages to incur return benefits to the investor as well which may bring disputes in the future resulting to implementation challenges [27].

#### **3.3 Growth environment challenges**

Complex hurdles are also encountered in legume adoption. These include the unfavorable soil types or climates that affect the components of legumes symbiosis benefits with other crops mainly on rotation and the presence of competition from rhizobia that compromises the process of nitrogen fixation, although yet ineffective. Legumes are also more difficult to grow many times than many cereals in an agronomic perspective. The other consideration is the introduction of the legumes to new environments which requires thorough selection of appropriate rhizobia-containing inoculants followed by their industrial manufacture which is a difficult process. Also, expertise required in the process to nature high-quality inoculant in manufacturing industries should be well trained in handling process and should not be underestimated [28].

Some of the factors limiting legume exploitation remains to be acknowledged from the key role of woody and herbaceous annual and perennial legumes in communal rangelands the drier and forest regions across the world. Where vegetation has not been disturbed or cleared for human benefits, majority of legumes and rhizobia are found in situ in these precious non-arable grounds. These repositories are now currently recognized for their extremely high conservation values particularly in ex situ germplasm centers which are becoming expensive to retain [29]. It is from there in situ natural repositories where many plant legumes and their root nodule bacteria (rhizobia) with unique prospect future roles in the field of agriculture, horticulture products and pharmaceutical medicine will be drawn.

#### **3.4 Difficulties in understanding and studying of the CT plants**

Despite this, the role of CT legume forage plants as an alternative to chemical anti-helminthic drugs is far from clear due to the results and conclusions from various research studies which vary greatly. This is for example in a study where little or no effect was noted in grazing experiments with neither sulla nor *L. pedunculatus*, where also variations in the effect on different worm-species were also observed. Several authors have reported reduction in *Teladorsagia circumcincta* infestation burdens but

not on *Trichostrongylus spp,* where effects were found on the intestines but not in the abomasum [30]. It is therefore not clear whether these disparities vary in CTs concentrations or the presence of different CT compounds in the feed diets*.*

#### **3.5 Uncertainties**

There are uncertainties regarding the CTs mode of action on worm population in the ruminants' stomachs. This is particularly driven in a case where there is unclarity whether the effects are due to direct anti-helminthic actions of CTs on various nematode stages in their life cycles to be specific. The effects of high protein diet intakes on the immunological competence of livestock have been well-established, although it does not necessarily explain all the anti-parasitic effects observed in pasture-grazing sheep which are high in meat protein as a result. Direct effects of worms have been also numerously reported in in-vitro studies, including worm-eggs inhibition and hatching and larvae migration of *H. contortus, T. circumcincta* and *Tr. colubriformis* with sulla extracts and its similar effects, birdsfoot trefoil, lotus, sainfoin, *Onobrychus viciifolia* and *Dorycnium spp.* on *Tr. colubriformis* on sheep and nematodes of deer. Similarly, there was decreased larval development in faecal droppings from sheep that were fed on chicory, *Dorycnium spp.* and *L. pedunculatus.* However, the significance of these study effects for the ideal natural situations is unclear as in vitro egg-hatching results have not been in accordance with the results from field experimental trials [31].

Therefore, further studies, both in vitro and in the fields, need to be conducted to indicate whether CT legumes containing forages will likely be a reliable effective addition to the non-chemical worm control strategies in livestock. The studies should as well report the CT concentration levels and proportions of the different worm species involved, as well as noting any production effects in relation to the animal in question. These mechanisms as well require much elucidation to explain any form of variable results that might be obtained in the proposed grazing trials. The identification of specific compounds linked with dose-administered dependent inhibitory effects against nematode developmental stages will aid in provision of an objective basis for the laboratory assay results in relation to those occurring in the field trials [32].

#### **3.6 Cost**

Authors of experimental sites have also reported that CT-containing legume forages are relatively more difficult and expensive to develop, establish and maintain than the traditional pastures [33]. Unless new legumes' economic importance is clear, both in terms of anti-helminthic effects and pasture-management cost and the sociological effects are considered, their general adoption may be compromised.

#### **3.7 Lack of knowledge and familiarity of many legumes**

Before we embark on a mass legume breeding program specifically for fish feeds, we should ask ourselves whether any natural occurring plant legume seeds contains the essential nutritional range considerations essential for aquaculture feeds. On research conducted by Assefam (2021), among the legume species adapted to different alkaline soils, *Trigonella balansa* was found to contain a relatively high significant omega-3 and omega-6 fats levels but a lower omega-3-omega-6 ratio that *T. glanduriferum.* A future broader legume family search may very clearly outline other agronomically adapted

*Future Use Prospects of Legumes through Improvement and the Challenges Faced DOI: http://dx.doi.org/10.5772/intechopen.109428*

plant legume species nutritionally-richer for aquaculture diets. Also, little is known regarding the essential reproductive, agronomic, rhizo-biological and physiological perennial legume forage trends in relation to other species such as *M. sativa, T. repens, T. pratense* and *Lotus corniculatus* which are much used commercially in many parts of the world [34]. This lack of knowledge is a serious constraint and challenge to the developing of other perennial legumes for future agricultural purposes.

#### **4. Conclusion**

Despite legumes widespread diverse benefits, most have neither been observed for their potential contribution to the primary production systems nor indeed their biologically active grain produce constituents. This book chapter has attempted to bring out some of the future use prospects to which legumes may be improved or manufactured for and the pathway to achieving these advancements. The genetic biodiversity of legume crops is currently constantly under much threat through the loss of natural habitats by humans for various benefits such as livestock rearing as discussed, overgrazing challenges or even illegal trading of medicinal plants across the globe. Of the 6000 known species of legumes, many are considered to be at a higher risk rate of extinction in the coming years. Currently, 10 *Trifolium* species native to the United States of America (USA) have been red flagged to be at a higher threat risk and their 16-world known common taxonomic classes are said to be endangered and vulnerable [35]. Medicinal plants for many centuries have also been used by farmers and pastoralists as a primary source of prevention and in the control of various diseases affecting livestock. With the rapid fading of ethnic traditional customs and cultures, some of the legume plants used in the making of organized traditional medicine will also, with no doubt, fade away too. It should become like a normal cultural practice now than ever more before that we should explore and try to put measures to preserve and conserve these plant species before they fade away and get lost from science completely. Just as most of the research in the field of Agriculture, and agronomy to be specific, on legumes is focused on yield increase in food and fiber crops, equally more emphasis should be put on research to identify the legume plants with potential to supplying of essential products in the pharmaceutical and nutrition industries in the current modern evolving society. This book chapter as well has put much attempt on the way forward prospections and anticipation on some of the roles that might be applicable and useful to the legume plants and their rhizomes. To quote, "We need to nodulate prokaryote plants". Researches focused on continued exploitation of the enormous natural genetic variations available in both legume forage plants and their constituent micro-symbionts will contribute greatly in the application of Biological Nitrogen Fixation (BNF), which is unarguably one of the key essential biological processes on the entire planet.

This chapter closes by concluding with a very important quote for Agriculturalists in whatever diverse fields, in general, and the entire people on planet earth always to remember to save essential plants with positive benefits to the ecosystem including man, therefore, "Save Plants that Save Lives".

#### **Thanks**

I would like to send my sincere gratitude and thanks to Blanka Gugic, who has been the personal Author Service Manager, IntechOpen, in the pioneering of the

writing of this chapter by extending the offer to contribute a chapter to this book entitled, "Production and Utilization of Legumes - Progress and Prospects", for all the support, encouragement and the advice as well as communication progress she has been offering all along. I am really glad and honored for her and much importantly I could not have done it without her, and thus, it would be a huge misfortune failing to honor her.

Thank you once again Blanka Gugic.

### **Author details**

Briggx Xavier Kenya Methodist University, Meru, Kenya

\*Address all correspondence to: xavierbriggx@gmail.com

© 2023 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

*Future Use Prospects of Legumes through Improvement and the Challenges Faced DOI: http://dx.doi.org/10.5772/intechopen.109428*

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### *Edited by Mirza Hasanuzzaman*

This book contains nine comprehensive chapters addressing various aspects of legume crop biology, production, and utilization. The contributions summarize recent findings on legume crop prospects and problems, and their responses to the environment. Management of legume crops under a changing climate, as well as their food value, are also discussed. This book will be useful for undergraduate and graduate students, teachers, and researchers, particularly in the fields of agronomy, crop science, and food science.

Published in London, UK © 2023 IntechOpen © Lightstar59 / iStock

Production and Utilization of Legumes - Progress and Prospects

Production and Utilization

of Legumes

Progress and Prospects

*Edited by Mirza Hasanuzzaman*