Abiotic and Biotic Stress Factors Affecting Storage of Legumes in Tropics

*Habtamu Kide Mengistu*

## **Abstract**

Tropical regions such as South Asia (SA) and Sub-Saharan (SSA) do have storage environment that may impose abiotic and/or biotic stress or. This book chapter aims to broaden current knowledge on the 'Abiotic and Biotic Stress Factors Affecting Storage of Legumes in Tropics'. This book chapter is prepared by including all relevant studies and detailed literatures using various scholastic search approaches. Typically, published papers and abstracts are identified by a computerized search of electronic data bases that include PubMed, Science Direct, Scirus, ISI Web of Knowledge, Google Scholar and CENTRAL (Cochrane Central Register of Controlled Trials). Thus, diseases, insects, etc…, are biological factors that cause biotic stress in plants while abiotic stress is caused by either physical or chemical factors. Biotic and abiotic stresses create adverse effects on multiple procedures of morphology, biochemistry and physiology that are directly connected with growth and yield of legume grains. It is, therefore, clear that the most important factors of food grains loss are moisture, temperature, metabolic activity and respiration, insects, mites, micro-organisms, rodents, birds and storage structures. Initial grain condition or quality of the seed for storage can indirectly be affected by abiotic stresses like water scarcity, high salinity, extreme temperatures, and mineral deficiencies or metal toxicities which reduce the crop's productivity. For maintenance of storage of initial grain's quality, grain must be dried and cooled prior to storage, the store must be constructed for blocking rodents and birds, enabling protection from sun and light entrance, allowing aeration to keep the temperature uniform in the store. Also, bringing the temperature of the grain down to below 12°C is necessary, since this temperature is a threshold at which microorganisms' reproductive activity is inhibited. Storage spaces with higher relative humidity (95%) and a temperature of 35°C, are detrimental for storage of legume grains. In general, legume grains should be attaining a temperature of about ≤ 10 °C before placing them in store. For storage safety, it is preferable to place the grain in the storage at moisture content of 13%, or less than 14% on wet basis. Also, combining drying and storage facilities in one and the same structure is economical, and allows further conditioning at later stages if required. In order to reduce postharvest loss from customs of traditional storage by farmers in tropics, governments should mobilize and integrate multidisciplinary management system of storage loss, and monitor precautionary measures of the stored grain throughout the storage period. They should be facilitating the selection and promotion of alternative, cost-effective and appropriate storage structures considering suitability to local conditions and sustainability.

**Keywords:** abiotic and biotic, legumes, stress factors, storage management, tropics

## **1. Introduction**

There are about 30 species of economically important legumes grown in the tropics [1–3]. Legumes such as soybean (*Glycine max*), common bean (*Phaseolus vulgaris),* lentil *(Lens culinaris),* groundnut (*Arachis hypogaea*), chickpea (*Cicer arietinum*), cowpea (*Vigna unguiculata*), and pigeon pea (*Cajanus cajan*) are the most frequently used species in tropics [1–3].

Legumes production in tropics is common, as these crops majorly aid the countries for securing food, source of income, providing nutrition and maintenance of soil fertility. It is reported that more than 101 million households in Sub-Saharan Africa (SSA) and more than 39 million households in South Asia (SA) grow one or more of these legume crops [4].

Crop losses occur at all stages of the post-harvest. Legume grains should retain both nutritional and all of the essential physiological functions of seeds for growth and therefore, it is preeminent to include storage methods and facilities enabling the quality preservation of these crops for further processing, packaging and marketing.

Storage of legume grains should be provided with certain conditions such as, fumigation to protect the store from undesirable microorganisms and should also be applying ventilation to adjust optimum temperature and humidity in the storage space for keeping quality of legume seeds.

Grain quality is characterized by physical properties, comprising kernel size, and sanitary characteristics, including microorganisms, rodent excrements, toxic seeds, pesticide residue and dust; inherent properties such as nutritional com¬pounds, biological viability and shelf life. However, smallholder farmers of SSA and SA have not yet understood how traditional storage methods affect these quality characteristics.

Therefore, this book chapter seeks to address the factors and major constraints affecting storage of legumes in tropics. It also, discusses conditions of safe storage, grain storage parameters and storage structures; probes management and control of grain loss in storage designs; and finally puts forward recommendations for future work.

## **2. Nature and properties of legumes**

Legumes belong to the botanical family called Fabaceae, which comprises over 750 genera and over 18,000 species, ranking third among other species within this family in the plant kingdom. Legumes are plants which belong to family called Papilionaceae within the order Fabaceae which is also called Leguminosae [5, 6]. Leguminosea can include species of trees, herbs, climbers, and shrubs in which only small number of these are consumed by humans. Legumes grain are the other species commonly served for food consumption by humans.

Common grain legumes include dry beans, lentils, soybeans, peanuts, fava beans, chickpea, mung bean, dry peas and green beans…, etc. [7]. Food legumes are divided into two groups, the first groups are all dry cultivated legume seeds, including pulses which are less in oil content and used for traditional food; the second groups are called oil seeds with high oil content such as soybean and peanuts, and they are used for extraction of edible oil [8, 9]. Legumes are globally consumed as an inexpensive meat alternative and are commonly served next to cereals [6]. Legumes are highly nutritious, providing essential amino acids, complex carbohydrates, fiber, unsaturated fatty acids, vitamins and important minerals [10, 11].

*Abiotic and Biotic Stress Factors Affecting Storage of Legumes in Tropics DOI: http://dx.doi.org/10.5772/intechopen.99413*

Legumes have been traditionally and widely cultivated crops served as major incorporate of children diet; hence, they are economically cheap and they can be used as alternatives or complements in diets comprising meat [6]. Legumes are highly nutritional containing essential proteins, unsaturated fats, complex carbohydrates, dietary fiber, essential minerals and vitamins [10, 11]. Legumes also possess beneficial bioactive phytochemicals [12] that have major roles in medicines concerning disease such as celiac, diabetes and cholesterol and weight management; as a result, they are recently processed as alternative for replacing animal based food products. Thus, it is obvious that incorporating legumes into various nutrition sensitive intervention programs is highly advisable, especially for developing countries, to reduce malnutrition and as means of income generation. Furthermore, legumes could be a base for the development of many functional foods as well as a range of feed and raw material for industrial products [13].

### **3. Factors affecting storage of legumes in tropics**

It is estimated that about 30% of the world's produced food is lost or wasted [14, 15]. This loss accounts about 1.3 billion milligram (mg) per year in a world where over 870 million people go hungry [16]. World Bank [17] indicated loss of food grains with an estimated cost of 4 billion USD for each year over the last decade. As a consequence, the total amount of grain loss exceeds the total amount of food aid to these countries. On the other hand, such losses are estimated to be equivalent to the annual caloric require-ment of 48 million people.

A significant increase in the food supply in Sub-Saharan Africa could be achieved by investing for reducing post-harvest food losses [17]. Thus, in recent times, experts advocate huge investments on postharvest loss (PHL) reduction to enhance food security [18].

Losses in food grains may fluctuate under different sets of ecological conditions. The quantitative and the qualitative losses occur due to factors of physical: temperature and moisture, biological: insects, rodents, mites, birds and meta-bolic activity of grains, chemical: breakdown of the produce and pesticides and engineering: structural and mechanical aspects. It is, therefore, clear that the most important factors of food grains loss are moisture, temperature, metabolic activity and respiration, insects, mites, micro-organisms, rodents, birds and storage structures.

#### **3.1 Abiotic stress factors affecting storage of legumes in tropics**

Moisture content, temperature and initial grain condition are the major abiotic factors affecting storage of legumes in tropics, whereas, the initial grain condition of seed can be negatively impacted for growth, development, yield and seed quality by abiotic stresses such as drought (water stress), excessive watering (water logging), extreme temperatures (cold, frost and heat), salinity and mineral toxicity [19].

#### *3.1.1 Moisture content*

All micro-organisms need moisture to maintain life. Keeping the moisture content of legume grains as well as their storage to be low will hinder the growth of microorgan¬isms; therefore, air should be prevented from entering the store. The moisture content below which micro-organisms cannot grow is called the safe moisture content [20]. All legume grains should be below their safe moisture content before they are placed in the storage space. In order to survive and multiply micro-organisms need moisture, and the safe moisture content is somewhat

related to the temperature at the time of storage. Thus, when stored below 27o C, the optimum safe moisture content for both broad bean and cow pea were observed to be 15.0 percent while the optimum safe moisture content for both lentil and pea were posited as 14.0% [21].

Grain stored within the proper moisture content may not remain in that condition, since moisture in the form of water, either from top lid or the side wall of the store may be dropped; or it might be down piped from a bucket elevator. Also, in some cases, moisture through cracks of storage may enter and wet the grain. During cold weather, when a warm grain having temperature of >10o C, or when a grain dried in dryer bin prior to storage, is cooled below -1o C in the store, then condensation happens particularly on the lid and from inside parts of storage space, and therefore, droplets on the amass cause increases in moisture content of the stockpile [22].

Due to excessive humidity, multiplication of fungi particularly *Aspergillus spp*., which produce dangerous toxins (*Aflatoxins*), will make legume grain unfit for human consumption [23]; therefore, The maximum permissible moisture content for safe storage of various crops is the moisture content in equilibrium with 70% relative humidity at about 27°C [21].

It is indicated in **Table 1**, that shelled groundnuts has lowest EMC among the listed legumes, which implies that at any given RH and temperature, legume grains seed which is rich in oil content will maintain lower moisture content than those enriched with other compositions such as lentil which is reach in protein.

## *3.1.2 Temperature*

Besides moisture, temperature is detrimental factor in accelerating or delaying the complex phenomena of the biochemical transformations, especially the "breathing" of the grain that influences the origin of grain degradation. Furthermore, it has a direct influence on the speed of development of insects, molds, yeasts and bacteria and on the premature and unseasonal germination of grain. The temperature within a store can be affected by sun, the cooling effect of radiation from the store, outside air temperatures and the heat generated by the respiration of both the grain and any insects present in the store [20]. It is noted that when the higher the temperature is, the lower must be the moisture of the grain in order to ensure good storage of the legume crops by minimizing the speed of development of these degradation phenomena, so that the temperature and moisture content of the grain conditions the maximal duration of storage.


#### **Table 1.**

*Equilibrium moisture content (EMC) values during storage of a range of legume crops at 70 percent relative humidity and 27°C.*

Moisture content of the stored grain should be monitored as a function of equilibrium moisture content of the air in the storage space. Many grain-degradation phenomena, if not completely blocked, can be slowed down by keeping the relative air humidity below 65–70 percent. In this sense, the "safeguard" moisture content is defined as that corresponding to equilibrium with the air at 65–70 percent relative humidity [21].

## *3.1.3 Initial grain condition*

Initial grain condition can be negatively affected by complex set of biotic and abiotic stresses. Abiotic stresses involve environmental factors that cannot be prevented, and they are the major factors which significantly reduce the crop's productivity and its post-harvest life and the storage life of the legume grain. Abiotic stresses include water scarcity, high salinity, extreme temperatures, and mineral deficiencies, particularly metal toxicities [24].

## *3.1.3.1 Drought stress*

Drought is a term that describes water scarcity in the soil, which can be influenced with seasonal variations. Thus, in general, various factors such as the amount of salt presented in soil causes drought stress which further leads to the flowing out of cellular water, leading to cell death as a consequence of contraction within protoplast of legume cell structure. Water deficit stress is damaging factor, because it inhibits photosynthesis by affecting the thylakoid membranes [25], and reduces nitrogen fixation of legume grains. Drought stress, therefore, is complicated abiotic stress that directly affects the intrinsic growth factors of legume grains imposing physiological deviations which indirectly affect quality of grain during later storage.

## *3.1.3.2 Extreme temperature stress (hot/cold)*

The metabolism of the legume grain cell can be damaged by an increase or decrease in respiration rate due to extreme temperatures. Abnormal anaerobic respiration produces unwanted metabolites that adversely shifts normal protoplasmic streaming with undesired electrolyte efflux imposing alterations occurring within normal cellular physiological metabolism that damages the protoplast. This can be revealed from cellular damage and reduced crop growth, thus, the crop will be rotten, and as a consequence end the life of crop [26]. Also, high temperatures can cause drought stress due to increased water loss by transpiration or evaporation; thus, elevated temperatures in the soil negatively influence the life of crops [27].

## *3.1.3.3 Salinity stress*

Salinity stress of legume grains occurs due to soil salinity or salinization, which is a phenomenon that happens when there is increased amount of salts in soil [28]. It mainly occurs in arid as well as semi-arid environments where the legume grain has higher evaporation and transpiration rates compared to precipitation volume throughout the year. Use of saline water in irrigation purposes, due to modification in soil content, and increased use of fertilizers besides inherent salts in subsoil [29]. Higher salinity in the soil imparts higher osmotic pressure potential and particular ion toxicity [30], that adversely impacts legume seed viability and vitality by inhibiting minerals and water, from being absorbed through leguminous roots, necessary for metabolisms in cytosol of cell membranes of leguminous seed, to enable of germination and normal physiological natural life cycle phases; as a consequence, it reduces the biological nitrogen fixation of legumes.

### *3.1.3.4 Metal stress*

Heavy metals that cause stress, (HMs) in legume plants are toxic inorganic compounds which cannot be biologically broken down into simpler form having negative effects on cells and genes, which impart mutagenic alterations and disruptions in chains of ecosystem surrounding the legume crop [31, 32]. Metals in soils such as iron, manganese, molybdenum, magnesium, zinc, copper, and nickel can be vital micronutrients for serving physiological life cycle of legume grains. Metals such as chromium, lead, cadmium, cobalt, selenium, arsenic, and mercury and silver, are non-essential elements with unknown physiological and biological function [33]. Legume grains require vital metal in smaller amount to carry out for their physiological and metabolic activities in cell, but disproportional coexistence of vital and non-essential metals generally lead to hindrance of normal physiological functioning, disturbance of protein structure as result of non-essential heavy metal bonding with sulpurhydryl building blocks bonding [34], and interfering with functional groups of significant cellular molecules [35].

### **3.2 Biotic stress factors affecting storage of legumes in tropics**

Biotic stresses factors of storage include all living organisms that bring damage to the crop in the form of biological, physical or chemical process. Thus, presence of toxins, productions of unwanted metabolites, deprivation of essential biological components of legume grain will facilitate deterioration of legume crop in storage spaces. It is the climate in which the legume crop lives, determines type of biotic stress that can be imposed on the crop, and influences the ability of the crop species to resist that particular type of stress [19].

#### *3.2.1 Microorganisms*

Damages or loss of grains vary generally as a function of crop variety, pest and insects, climate, system of harvesting, system of processing, storage, handling and marketing [36]. The main agents causing deterioration of stored legume grains are microorganisms (fungi, bacteria, yeast and mold), insects and mites, rodents, birds, and metabolic activities. The principal micro-organisms (fungi and yeasts), which attack grains, are very dangerous as they cannot be easily seen with naked eyes and their harmful influence spreads very quickly and renders whole grains waste. Anaerobically respiring species of storage fungi grow more quickly at the optimum growth temperature of about 30°C and below RH of 95 percent [5].

Biotic factors particularly mold (fungi) and insects influence longevity of seed in storage. The two fungi types that attack legumes seed are field fungi and storage fungi. Field fungi affect seed in the field prior to harvesting, and storage fungi attack seed during storage. Field fungi (e.g., *Fusarium spp*.) thrive in high moisture environments, during high moisture level of seed due to rainfall at the time of harvesting [37]. Storage fungi (*Aspergillus spp*.) thrive best when moisture levels of seed are low. Storage fungi do not establish on seed with MC in equilibrium with equilibrium moisture content (EMC) of less than 68% ambient RH [37]. Therefore, when moisture content, temperature, and relative humidity are low, the risk of fungi invasion is minimized. These fungi produce harmful stuff that is injurious to seed cells and cause seed deterioration. Inadequate drying of seed can favor the growth of molds or fungi, hence a decrease in seed quality or quantity. Bacteria prevalence to the stored legume grains may be low. They may, however, invade already damaged portion of the crop products during storage and their

multiplications. Deterioration by bacteria is limited as they require free water to grow. Storage bacteria are active around 90% RH where fungi are already very active [38].

## *3.2.2 Insects and mites*

Insects and mites could seriously attack stored legume grains when there is warm and humid storage environment. They pierce the kernels, consume on the outer covering skin and the inner nutritious endosperm of legume seed, respiring off water which facilitate development of undesirable molds and fungi [36].

Insects are inactive below seed moisture content of 8% while they are active around seed moisture content of 15%. To inhibit growth of insects in the storage, the moisture content of legume grain should be reduced below 8%, while H and temperature within the store should be kept below 40 percent and 10°C, respectively. The most suitable moisture content and temperature of grains for the growth of insects are about 11–15 percent and 28°C - 36°C, respectively [39].

Mites are distinct from insects, hence, at the adult stage they possess eight legs and their bodies are not divided into a head, thorax and abdomen. Thus, insects are generally much smaller than insects. Mites are usually seen, if they are large in number and visible as dust on the surface of bags. Mites are generally not a problem in tropical countries like India because they require low temperature, but when they become active, they spoil 2–3 percent of annual produce [5].

## *3.2.3 Rodents*

Among the various pests detrimental to the wellbeing of man, rodents form an important group and assume great economic importance. During the pre-harvest stages, they cause considerable damage to crops at all stages of growth. In storage they do not only consume large quantities of food stuffs, but also contaminate the food stuff with their excreta, destroy containers by gnawing holes which lead to leakage and wastage of grains and paw into and scatter grains while they eat. Thus, the scattered grains along with that which leak from gnawed holes, are subjected to contamination and admixture with impurities. Damage to grains stored in bulk is less than to grains stored in bags because rodents are unable to burrow into the bulk [21].

## *3.2.4 Birds*

Like rodents, birds also destroy grains by making holes in stacks and feed on grains as well as contaminate the grains through droppings and feathers. Damage directly occurs by birds when grains are being sun dried, and consequent damage occurs when grains are in storage. Losses caused by birds can be avoided by preventing their access to the stored commodities. The birds which cause damage are pigeon (*Columba livia*), crow (*Corvus splendens*) weaver bird (*Ploceus philippinus*), sparrow (*Passer domesticus*) and black bird (*Acrldotheres tristis*) [21].

## *3.2.5 Metabolic activities*

Legume grains are living materials and their normal chemical reactions produce heat and chemical reactions by products [36]. Heat is released as result of exothermic reaction and water is respired off by microorganisms plague, as a by-product of the enzymatic catabolism of nutritious constitutes of seed, used as substrates for synthesis of cell material. Thus, increased temperature and moisture content highly facilitate deterioration of seed in store by microorganisms.

Even though legumes are low in their carbohydrate, microorganisms under aerobic condition will completely convert the small amount of carbohydrates, or endosperm to CO2, H2O and produces energy in the form of ATP as shown in the following equation:

$$\text{C}\_6\text{H}\text{I}\_2\text{O}\_6 + \text{6O}\_2 \rightarrow \text{6CO}\_2 + \text{6H}\_2\text{O} + \text{Energy} \,(\text{ATP}) \tag{1}$$

Metabolic processes cause two types of losses in the store. The first type is the loss due to the enzymatic catabolism of substrates i.e., synthesis of cell material of grain converted by microorganism to carbon dioxide and water. The other loss occurs when entire of individual grains loose its biological constitutes consumed by microorganism [36].

#### **3.3 Storage structures**

The structures and materials from which the store is built, determines safety of grains in store since legume grains should be protected from exposure of sun and rain. Storage structure should facilitate adequate ventilation for monitoring temperature which is appropriate to maintain grain quality in the store. Stores should allow space for inspection and detection for occurrence of disease arising early in the grains [21].

## **4. Constraints affecting storage of legumes in tropics**

Constraints to the development of major tropical grain legumes which are soybean, cowpea, pigeon pea, groundnut and common bean can be technical issues, and are called technical constraints. Thus, to manage and control deterioration of these grains during storage, technical constraints need to be understood for the effect on the crop ecosystem, attributing to abiotic and biotic factors, which are negatively affecting the development and storage of legume grains. Other constraints are institutional which arise from and within the government's agricultural policies and regulations, paying less focus on practicing in solving technical constraints of crop storage management system. Institutional constraints include policies, that do not introduce, motivate and process the release of stress resistant and durable legume varieties; lack of setting regulatory laws on principles that intend for safe storage; lack for investments engaged in research and development of storage equipment and post-harvest storage mechanisms and technologies [4].


#### **Table 2.**

*Major disease causing microorganisms in storage of common legume grains in tropics.*

A large number of diseases, insects and parasitic weeds cause varying levels of damage to tropical grain legumes at different stages of growth – from seedling to storage.

It is indicated in **Table 2**, that *Maruca* (pod borer), bruchids, aphids and *Fusarium oxysporum* which causes fusarium wilt are some of the common disease causing microorganisms that are constraints for legume storage in tropics.

## **5. Conditions of safe storage**

The grain, microorganisms and foreign material together form an artificial ecosystem in store. Grain quality can decline in the store as a consequence of chemical, biological and physical processes. These processes are influenced by factors such as are moisture, temperature, carbon dioxide and oxygen, initial biological state of the grain, microorganisms and insects, rodents, birds, whether conditions, cleaning, drying, cooling and ventilation. Among these factors, moisture content and temperature of legume kernels, are major factors to influence for bioprocesses in the grain [21].

Thus, storage spaces with higher relative humidity, which is 95% and a temperature of 35°C, are detrimental for storage of seeds [40]. In order to prevent moisture movement due to temperature gradients within each load, grain should be placed into storage with a temperature ranging 10 to −9°C. In general, the grain should be attaining a temperature of 10°C or below before placing it in store. Moisture values, on wet basis, which are commonly 13, 14 and 15.5 percent are maximum moistures recommended for any storage, thus, should not exceed these, for safe storage of crop load. For storage safety it is preferable to place the grain in the storage at moisture content, on wet basis, of 13 percent, or less than 14 percent [40].

## **5.1 Drying for safe storage**

In general, the life of the seed during storage revolves around its moisture content, storage temperature and humidity. However, the processed seed has better storability. The rate of deterioration of crop seeds increases as respiration goes up with high moisture content (MC). The effect of seed moisture content has been generalized as safe for sealed storage at 6–10% MC at which no pest activity occurs; while fungi, bacteria and insects grow at 12–14% MC and heating occurs at 18–20% MC unless aerated, and in further, germination occurs at 45–50% MC [41, 42]. The safe drying temperatures for seeds with moisture ranging over 22% MC is 55°c and 40°c for seeds with moisture content below 22% [41, 42]. In many cases, facilities for drying and storage are found in one and the same structure. Combining these functions is economical and it allows further conditioning at later stages, if required. However, there are situations where storage is considered quite separately from drying, ranging from the storage of naturally dried crops to the storage of grain dried by a continuous-flow or batch dryer. Utmost, care should be exercised in drying seeds to a safe limit, and thus, good storage should not allow further absorption of moisture.

## **5.2 Management and control of loss in storage designs and structures for tropical legumes**

Since quality of grain can be affected through the entire food chain and this implies storage is concerned only with maintaining the initial quality of legume grains. Hence, clean grain should go into storage, it is necessary to remove weeds and debris from legume grain seeds. Also, the area presented around the storage site should be free of dirt and the store must be cleaned and kept free from remnants of previously stored grain. Cleaning for harvesting and handling equipments before carrying out the harvest activities will minimize risk factors for grain's quality during storage. During placing legume grain in the store its quality can be facilitated using a rotating grain cleaner, and finally cooling the grain to the existing outside air temperature (that most usually occurs) as soon as it is put into the storage.

## *5.2.1 Temperature*

The temperature at which food is stored is very critical to shelf life. The best range for food storage is a constant temperature between 40 and 60 degrees and void freezing temperatures [21]. Hence, controlling the temperature of small stores is not technically and economically feasible, reducing the moisture content of the stored produce are necessary. In storing dry grain for longer periods or keeping wet grain in stores for a short period of time, it is important to move air through the grain mass, so as to control grain temperature. This become obvious in the spring, when outside air temperatures begin to warm and cause convection air currents inside the store as a consequence of differences in grain temperatures which can move and concentrate moisture in the top center of the storage spaces [21]. Wet grain and molds give off heat through respiration which indirectly contributes for mold growth. Thus, mold growth can be inhibited by keeping the grain and the store cool through application of aeration. Even if grain is dry and cool when placed in storage, aeration is needed to keep temperature uniform within the store to provide the grain mass temperature [21].

## *5.2.2 Moisture*

The moisture content of seed during storage is most detrimental factor affecting the shelf life. Legume grains should have a 10% or less moisture content for long term storage. It has been reported that seed moisture content of about 6–8% is optimum for maximum longevity in storage of most crop species. Keeping oily legume grains below moisture content of 4–6% impose lipid autoxidation. Seeds are hygroscopic in nature, and as a consequence, they can pick up moisture from and releases it to the surrounding air [43]. Moisture levels above safe moisture content can be tolerated when storing seed for short period. The sitting and ventilation of the store are important so as to reduce storage problems due to condensation. Low night temperature can cause the walls of a store cooled below their dew point, as a result, condensation can occur near the edge of the store increasing the moisture in the grain layers.

## *5.2.3 Microflora, insects and mites*

Microorganism's activity can lead to quality deterioration in store by causing loss of grain viability. The microflora activity inside the store is monitored as a function of the correlation between relative humidity in the store, temperature and moisture content of seed and the store. Insect activity in the store increases and reaches maximum with a temperature ranges of 19.5 -°C 33°C and the temperature should be below 17°C. Fumigants and insecticides are chemical methods applied to control insect activity. Applying fumigation, which are highly effective chemical insecticides, environmental friendly and safe for human use, enables control of insects in the store and facilitates longer period of storage [43].

#### *5.2.4 Grain storage parameters and storage structures*

For maintenance of initial grain quality storage, grain must be dried and cooled prior to storage; the grain should be protected from insect attack. The store must be constructed in a way to enable blocking of rodents and birds and also enabling protection to sun and light entrance, allowing ventilation so as to keep the temperature uniform in the store. Pulses stored above 12% moisture content (MC) require aeration to maintain quality. Cooling grain in the store cannot be treated with protectants since these chemicals leave harmful residues that may be presented till time of consumption by human.

Application of fumigants and insecticides are the two methods commonly recommended to control pests in store. This requires a gas-tight, sealable storage. Grain Research and Development Corporation (GRDC) noted that efficient handling techniques that minimize physical damage of legume grains should be used in order to minimize the possible attack by insects that may produce additional damage through unwanted chemical and biological processes [44]. Aeration, whereby ambient or artificially cooled air is used, is primarily a grain preservation technique [45–48]. Bringing the temperature of the grain down to below 12°C, is necessary since this temperature is a threshold at which microorganisms reproductive activity is inhibited [45, 48–51].

## **6. Conclusion**

Abiotic and biotic factors are the overall factors contributing to pre-harvest and post-harvest losses of legume crops in tropics. Abiotic stress factors such as drought, salinity, extreme temperature, toxic metals are those determining the crop productivity at the soil stages which, in further, affect initial legume seed's quality for storage. Temperature, moisture and initial grain quality are the most important factors that determine storage of legume crops. Mold and insects are the major biotic factors affecting grain quality in store. Moisture content and temperature of the grain as well as the store has to be monitored throughout storage period. Well -designed storage system should be constructed and provided with adequate ventilation capacity. Regular checking of grain condition and monitoring through proper preventative actions has to be applied before significant deterioration of legume grains happened in the stored. Hence, protectants are not advised to be used as they mostly impart residues which negatively affect the health and safety of consumers, so that it is recommended to selectively use fumigants and insecticides which do not disrupt sustainability of ecosystem, and those which do not leave residues on legume grains so as to avoid negative healthy impacts to human during consumption. For effective control and management of the biotic and abiotic deteriorative factors that affects grain quality in the store, it is important to understand individual and correlated characteristics of the physical, chemical and biological processes related to these deteriorative factors, so that selecting effective way of reducing the initiates of these processes at pre- harvest and post-harvest stage will be possible, helping the design and construction of safe storage.

#### **7. Recommendations**

In order to reduce the factors of pre-harvest loss that contributes to the postharvest loss occurring during storage, the governments in tropics should be establishing soil productivity and preservation polices supported by research studies

and outputs for monitoring and controlling the usage of selected and appropriate fertilizers, establishing grading and storage standards for tropical legume grains, and allocating incentive for private investment in seed production with better storage durability. They should also use an integrated multidisciplinary management, monitoring, and precautionary measures of the stored grain throughout the storage period. The governments should be strategically selecting, promoting of alternative cost-effective/appropriate storage structures, considering suitability to local conditions and sustainability. Moreover, establishing suitable policies and regulations that enable on variety release process in short period of time, increasing investment in agricultural research and development, and many others are pivotal prospects that governments in tropics should focus to reduce loss of legumes, and legumes' quality during storage.

## **8. Scope of future work**

Future work regarding of reducing storage loss in tropics, should focus on assessing and testing grain quality and identify causes of deterioration in the existing traditional storage systems, and filling the gaps along with the overall efforts in improving and promoting of these storage systems. Assessing hygienic quality of farmers and training farmers for principles and procedures in handling and storage of legume grains, in order to avoid risk for deterioration factors during storage. Establishing safe storage moisture limit guidelines for legume crops and monitoring system, which will also ensure functioning of these guidelines during all seasonal variations for storing legumes, indigenous to countries in tropics.

## **Acknowledgements**

The author would like to thank Professor Geremew Bultosa for his advice and information during the preparation of this review paper. My gratitude goes to for his constructive information and material support.

## **Conflict of interest**

The authors declare no conflict of interest.

## **Special thanks**

I would like to thank Jasna Bovic, author service manager at IntechOpen Limited Organization, for motivating me and putting her best effort for the publication of this book chapter. I would like to thank IntechOpen Limited Organization for giving me the chance of writing this chapter, and for covering most of the publishing cost.

*Abiotic and Biotic Stress Factors Affecting Storage of Legumes in Tropics DOI: http://dx.doi.org/10.5772/intechopen.99413*

## **Author details**

Habtamu Kide Mengistu Department of Food Science and Postharvest Technology, Haramaya Institute of Technology, Haramaya University, Ethiopia

\*Address all correspondence to: habtamu.kide@haramaya.edu.et; habtamukidemengistu@gmail.com

© 2021 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.

## **References**

[1] Baldev B, Ramanujam S, Jain HK, editors. Pulse Crops (Grain Legumes). New Delhi: Oxford and IBH Publishing Co. Pvt. Ltd; 1988. 626 pp.

[2] Raemaekers RH, editor. Crop Production in Tropical Africa. Directorate General for International Cooperation, Ministry of Foreign Affairs, External Trade and International Cooperation, Brussels, Belgium; 2001. 1549 pp.

[3] Upadhyaya, H.D., Dwivedi, S. L., Gowda, C. L. L., & Singh, S. Identification of diverse germplasm lines for agronomic traits in a chickpea (Cicer arietinum L.) core collection for use in crop improvement. Field Crops Research. 2007; *100*(2-3), 320-326.

[4] Abate T, Shiferaw B, Gebeyehu S, Amsalu B, Negash K, Assefa K, Eshete M, Aliye S, and Hagmann J. A systems and partnership approach to agricultural research and development – lessons from Ethiopia. Outlook on Agriculture. 2011; 40(3):213-220.

[5] Staniak, M., Bojarszczuk, J., & Księżak, J. The assessment of weed infestation of oats-pea mixtures grown in organic farm. Journal of Research and Applications in Agricultural Engineering. 2014; *59*(4).

[6] Kouris-Blazos A, Belski R. Health benefits of legumes and pulses with a focus on Australian sweet lupins. Asia Pacific journal of clinical nutrition. 2016 Jan;25(1):1-7.

[7] Yorgancilar M, Bilgiçli N. Chemical and nutritional changes in bitter and sweet lupin seeds (Lupinus albus L.) during bulgur production. Journal of food science and technology. 2014 July; 51(7):1384-1389.

[8] Maphosa Y, Jideani VA. The role of legumes in human nutrition. Functional food-improve health through adequate food. 2017 Aug 2; 1:13.

[9] Singh AK, Singh SS, Prakash VE, Kumar S, Dwivedi SK. Pulses production in India: Present status, sent status, bottleneck and way forward. Journal of AgriSearch. 2015 Jun 1; 2(2):75-83.

[10] Bouchenak M, Lamri-Senhadji M. Nutritional quality of legumes, and their role in cardio metabolic risk prevention: a review. Journal of medicinal food. 2013 Mar 1; 16(3): 185-198.

[11] Rebello CJ, Greenway FL, Finley JW. A review of the nutritional value of legumes and their effects on obesity and its related co-morbidities. Obesity reviews. 2014 May; 15(5):392-407.

[12] Phillips RD. Starchy legumes in human nutrition, health and culture. Plant Foods for Human Nutrition. 1993 Nov; 44(3):195-211.

[13] Hueda MC, editor. Functional Food: Improve Health through Adequate Food. BoD–Books on Demand; 2017 Aug 2.

[14] FAO-World Bank. Reducing postharvest losses in grain supply chains in Africa. Report of FAO-World Bank workshop held from 18-19th March 2010 in Rome, Italy. 2010. pp. 120.

[15] Prusky D. Reduction of the incidence of postharvest quality losses, and future prospects. Food Security. 2011 Dec;3(4):463-474.

[16] Gustavson J, Cederberg C, Sonesson U, van Otterdijk R, Meybeck A. Global food losses and food waste. Swedish Institute for Food and Biotechnology (SIK), Gothenburg, Sweden. 2011:1-37.

[17] World Bank. Missing food: The case of postharvest grain losses in

#### *Abiotic and Biotic Stress Factors Affecting Storage of Legumes in Tropics DOI: http://dx.doi.org/10.5772/intechopen.99413*

sub-Saharan Africa. Report number 60371-AFR, World Bank, Washington, USA. 2011b.(pp. 1-96).

[18] (GIZ) GmbH. Reducing postharvest losses conserves natural resources and saves money. Report of GFFA Expert panel discussion. Berlin, 2013 Jan 18;pp. 30-50.

[19] Gull A, Lone AA, Wani NU. Biotic and abiotic stresses in plants. Abiotic and biotic stress in plants. 2019 Oct 7:1-9.

[20] Tilahun S. 'Grain based Ethiopian traditional common foods processing science and technology. Training module for center of research on grain quality, processing and technology transfer, Haramaya University, Ethiopia. 2007.

[21] Dubale Befikadu. Factors Affecting Quality of Grain Stored in Ethiopian Traditional Storage Structures and Opportunities for Improvement. International Journal of Sciences: Basic and Applied Research (IJSBAR); 2014. Volume 18, No 1, pp. 235-257. http: // gssrr. org/index. Php? Journal =Journal Of Basic And Applied.

[22] Denlinger DL, Lee Jr RE, editors. Low temperature biology of insects. Cambridge University Press; 2010 Jan 28.

[23] Turner PC, Sylla A, Gong YY, Diallo MS, Sutcliffe AE, Hall AJ, Wild CP. Reduction in exposure to carcinogenic aflatoxins by postharvest intervention measures in west Africa: a community-based intervention study. The Lancet. 2005 Jun 4; 365(9475):1950-1956.

[24] Cramer GR, Urano K, Delrot S, Pezzotti M, Shinozaki K. Effects of abiotic stress on plants: a systems biology perspective. BMC plant biology. 2011 Dec; 11(1):1-4.

[25] Ashkavand Z, Sadeghi E, Parvizi R, Zare M. Developed Low-Temperature

Anionic 2H-MoS2/Au Sensing Layer Coated Optical Fiber Gas Sensor. ACS Applied Materials & Interfaces. 2020 Jul 2; 12(30):34283-34296.

[26] Devasirvatham V, Tan DK. Impact of high temperature and drought stresses on chickpea production. Agronomy. 2018 Aug;8(8):145. Devasirvatham V, Tan DK. Impact of high temperature and drought stresses on chickpea production. Agronomy. 2018 Aug;8(8):145.

[27] Takahashi D, Li B, Nakayama T, Kawamura Y, Uemura M. Plant plasma membrane proteomics for improving cold tolerance. Frontiers in plant science. 2013 Apr 17; 4:90.

[28] Bockheim JG, Gennadiyev AN. The role of soil-forming processes in the definition of taxa in Soil Taxonomy and the World Soil Reference Base. Geoderma. 2000 Mar 1; 95(1-2):53-72.

[29] Carillo P, Annunziata MG, Pontecorvo G, Fuggi A, Woodrow P. Salinity stress and salt tolerance. Abiotic stress in plants–Mechanisms and adaptations. 2011 Sep 22; 1:21-38.

[30] Akbari G, Sanavy SA, Yousefzadeh S. Effect of auxin and salt stress (NaCl) on seed germination of wheat cultivars (*Triticum aestivum L*.). Pakistan journal of biological sciences: PJBS. 2007 Aug 1; 10(15):2557-2561.

[31] Flora SJ, Mittal M, Mehta A. Heavy metal induced oxidative stress & its possible reversal by chelation therapy. Indian Journal of Medical Research. 2008 Oct 1; 128(4):501.

[32] Wuana RA, Okieimen FE. Heavy metals in contaminated soils: A review of sources, chemistry, risks and best available strategies for remediation. ISRN Ecology. 2011; 2011:1-20.

[33] Schutzendubel A. Plant responses to abiotic stresses: Heavy metal-induced

oxidative stress and protection by mycorrhization. Journal of Experimental Botany. 2002; 53(372):1351-1365.

[34] Hall JL. Cellular mechanisms for heavy metal detoxification and tolerance. Journal of Experimental Botany. 2002; 53(366):1-11.

[35] Hossain Z, Mustafa G, Komatsu S. Plant responses to nanoparticle stress. International Journal of Molecular Sciences. 2015; 16(11):26644-26653.

[36] Fekadu L. Fundamentals science and technology of food grain drying, cleaning and storage practices". In Training module for center of research on grain quality, processing and technology transfer, Haramaya University, Ethiopia. Haramaya University, Ethiopia. 2007.

[37] Bewley, J. D., Bradford, K. J., Hilhorst, H. W. M., & Nonogaki, H. Seeds: Physiology of development, germination, and dormancy, 3rd Edition. New York-Heidelberg Dordrecht London: Publisher' Graphics LLC. Springer; 2013. pp. 346-364.

[38] Malik CP. Seed deterioration: a review. International Journal of Life Sciences Biotechnology and Pharma Research. 2013; 2(3):374-385.

[39] Darfour, B. Controlling the deterioration of harvested grain/seed to improve food security [Graduate Theses and Dissertations]. 2019.

[40] Fikirte Assefa, Kalyani Srinivasan. Effect of Relative Humidity and Temperature on Shelf Life of Sorghum, Lentil and Niger Seeds. International Journal of Applied Agricultural Sciences. Vol. 2, No. 6, 2016, pp. 83-91. doi: 10.11648/j.ijaas.20160206.12.

[41] Sahay KM, Singh KK. Unit operations of agricultural processing. Vikas Publishing House Pvt. Ltd.; 1996. [42] Michael AM, Ojha TP. Principles of Agricultural Engineering: Agricultural surveying, irrigation, agricultural drainage, soil and water conservation. Jain Brothers; 1966.

[43] Kartoori Sai Santhosh Ram. Factors Affecting Seed Deterioration [internet]. Seed Science & Technology. [Accessed: 2015 Feb17]. pp. 13-50. https://www. slideshare.net/saikalebu/factorsaffecting-seed-deterioration.

[44] GRDC. Stored grain pests identification: The back pocket guide. GRDC,[internet]. 2011. Available from: https: //grdc. com.au/resources-andpublications/allpublications/ publications/2016/09/grdc-bpg stored grain pests. [Accessed 2016 Sep].

[45] Burges HD, Burrell NJ. Cooling bulk grain in the British climate to control storage insects and to improve keeping quality. Journal of the Science of Food and Agriculture. 1964 Jan; 15(1):32-50.

[46] Berhaut P., Lasseran J.C. Conservation durable par Ia ventilation. Perspectives Agd- (ITCF). 1986.97. 32-39.

[47] Brunner H. Cold preservation of grain. Proceeding. 4 the Int. Works Coot Stored· product protection. Tel Aviv. 1986 Sept. *In*: E. Donahaye & S. Navarro Eds. 1986. pp 219-229.

[48] Armitage DM. Controlling insects by cooling grain. Monograph-British Crop Protection Council. 1987.

[49] Granovsky TA, Mills RB. Feeding and mortality of *Sitophilus granarius* (L.) adults during simulated winter farm bin temperatures. Environmental Entomology. 1982 Apr 1; 11(2):324-326.

[50] Fleurat Lessard F. Control of storage insects by physical means and modified environmental conditions. Feasibility and applications. Monograph-British Crop Protection Council. 1987(37): 209-218.

*Abiotic and Biotic Stress Factors Affecting Storage of Legumes in Tropics DOI: http://dx.doi.org/10.5772/intechopen.99413*

[51] Lessard FF. Control of storage insects by physical means and modified environmental conditions. Feasibility and applications. Monograph-British Crop Protection Council. 1987.

## **Chapter 10**
