**1. Introduction**

New semi-dwarf, disease-resistant, and high-yielding cultivars have been created as a result of the green revolution [1]. This innovative agricultural technique raised annual yields, which increased the amount of food produced by vital crops [2]. On the other hand, commercial crops have a very small genetic base, making them vulnerable to environmental dangers. Up to 75% of agricultural genetic variety has already been lost, and another 15–37% are in danger of going extinct [3]. Out of the 200,000 plant species, humanity has historically used roughly 3000 for food production. Only 15–20 of these are now used to produce food [4]. Therefore, addressing this issue poses a significant

challenge for breeders, and creating plans to boost genetic diversity has drawn the interest of numerous research teams [5, 6]. Mutation breeding can be used to address these problems by developing agricultural varieties with superior product quality, larger yields and yield stability, more resistance to climatic change, and greater tolerance to biotic and abiotic stresses [4]. More than 9 million hectares of mutant varieties are planted annually, producing about 1.5 million tons of crops annually with an estimated worth of roughly \$500 million [7]. Mutagenesis is a coherent tool for generating variation in crop species in a short period compared to crosses [8]. Also, mutations can be analyzed using forward genetics (from phenotype to gene) or reverse genetics (from gene to phenotype to understand gene function [5]. A mutation is a heritable change in a gene, chromosome that contains several genes, or a change in a plasmagene [9]. And mutants are individuals who exhibit modified traits as a result of heritable changes [10–13]. Mutations are generated from errors in DNA replication or from the damaging effects of mutagens, such as chemicals and physical elements, which interact with DNA and change the architecture of individual nucleotides, including substitutions, insertions, or deletions, to create novel mutant lines with improved traits and increase plant genetic diversity [14–16]. However, spontaneous mutation rates in plants are low [17]. Therefore, increasing the frequency of mutations by mutagenesis is a significant way to obtain the raw materials required for the development of desirable "smart" crop types that boost biodiversity [18]. For more than 70 years, plant breeders have used mutation induction and detection two crucial components of mutation breeding to increase the genetic diversity of plants and create novel mutant lines with enhanced traits [19]. A practical approach to deal with climate change is the creation of new cultivars with improved agronomic features, such as increased resilience to biotic and abiotic stress, and bio-fortification [20]. This chapter will emphasize the value of mutant breeding to enhance plant biodiversity and genetic resources for the intensification of crop production.

### **2. Mutation breeding**

De Vries [21] popularized the concept of developing new forms through induced mutations. The first conclusive proof of ionizing radiation's capacity to produce mutations was provided by [22]. When he was successful in altering Drosophila in a specific way. Three categories of mutagen can be known: physical, chemical, and biological. Physical mutagens include gamma rays, X-rays, electron beams, ion beams, and neutron particles. Chemical mutagens: Substances include ethyl methane sulphonate (EMS), sodium azide (NaN3), diethyl sulfate (dES), N-ethyl-N-nitrosourea (ENU), and ethyleneimine (EI); biological mutagens: microorganisms like bacteria and viruses [23]. Some investigations have shown that the combination of these chemicals increases the frequency of mutations [6]. A mixture of chemical and physical factors was observed in rice that had been exposed to rays and subsequently had its seeds soaked in EMS. Salinity-tolerant mutants were isolated and were able to survive for up to 15 days in a 342 mM NaCl solution, while the control was affected by 171 mM NaCl after 5 days [24]. Siddiqui and Singh [25] found that the combination of different doses caused reductions in panicle number, plant height, and 100-seed weight when they utilized a combination of rays, EMS, and Sodium Azide in Basmati rice. A mutation is a change in a small section of a genome's nucleotide sequence. One nucleotide is frequently replaced by another in point mutations; other changes involve the insertion or deletion of one or more nucleotides (**Figure 1(A)**).

*Induced Mutation to Enhance Plant Biodiversity and Genetic Resources for Intensification… DOI: http://dx.doi.org/10.5772/intechopen.108117*

#### **Figure 1.**

*(A) A mutation is a minor change to the DNA molecule's nucleotide sequence. (B) Mutations that arise as a result of mutagenesis activity and replication errors are fixed by DNA repair. (C) Recombination processes include the exchange of DNA molecule segments [14].*

The primary origin of mutations is errors in DNA (deoxyribonucleic acid) replication or the corrosive effects of mutagens, such as chemicals and radiation, which interact with DNA and alter the architecture of individual nucleotides [14, 26]. DNA repair enzymes are present in every cell and work to reduce the frequency of mutations. These enzymes use two techniques. Some are post-replicative, checking newly synthesized DNA for errors and fixing any that they find, while others are pre-replicative, searching the DNA for nucleotides with odd structures that are replaced before replication takes place (**Figure 1(B)**). When homologous chromosomal segments are exchanged during meiosis or when a mobile element is transposed from one place to another inside or between chromosomes, for example, recombination causes the rearrangement of a section of the genome (**Figure 1(C)**). Induced mutation is currently the method of developing novel improved germplasm in crop plants [27]. On the good cultivars, mutagens are typically applied. As seen in **Figure 2**, mutation breeding speeds up the process of creating new varieties as compared to hybridization.

Additionally, mutant types exhibit a better survival rate in the face of environmental changes, making it possible to distinguish between mutants with different traits through mutation breeding. Because mutations can occur in any gene and are unpredictable, we also stand a fair possibility of discovering novel traits. For example, tolerance for salt in sesame and *Orobanche* in faba beans. Also, the analysis of mutants by forward genetics (from phenotype to gene), or by reverse genetics (from gene

**Figure 2.** *Diagram of crop plant breeding for mutations [28].*

**Figure 3.** *The five largest countries registered mutant lines as commercial varieties [19].*

to phenotype), can be applied to realize gene function [5]. The induced mutation method was used in some countries to enhance crop productivity because of its efficacy and wide adoption (**Figure 3**).

The sources of genetic diversity in plant species can be categorized into three groups, depending on the mechanisms underlying the diversity: (1) cultivars, or crops that humans have artificially selected based on advantageous phenotypic traits; (2) naturally occurring variations selected over a long period of time; and (3) mutants produced using transgenic technologies or chemical/physical mutagens [29]. According to Mba [30], the common practical factors that must be taken into mind when inducing and detecting mutations are as follows:


IAEA has divided its mutant varieties into four categories based on their intended uses: (1) direct use of a mutant line created through somaclonal variation or physical and chemical mutagenesis; (2) indirect use of a mutant line; (3) use of mutant gene alleles (traits), such as the rice Calrose 76 sd1 allele (semi-dwarf 1 trait); and (4) use of wild species' genes inserted into plant genomes [31].

A successful mutation breeding program starts with goals that are well-defined, such as improving a particular plant phenotype or genotype by enhancing the distinctive traits of one or more elite lines, inducing a morphological marker, establishing distinctness in a promising line to meet the requirement for variety registration, or inducing male sterility or fertility restoration to make a line useful as a component for *Induced Mutation to Enhance Plant Biodiversity and Genetic Resources for Intensification… DOI: http://dx.doi.org/10.5772/intechopen.108117*

**Figure 4.** *Mutant lines registered as commercial varieties [19].*

the creation of hybrid varieties [32]. The agronomic traits are confirmed in the second and third generations by clear phenotypic stability, and further evaluations are done in the generations after that. In comparison to the original variety, mutant screening involves selecting individuals from a large population of modified individuals who match specific selection criteria, such as early or disease resistance [33]. Through screening procedures like those for salt and drought tolerance, or disease resistance, mutant phenotypes can be found. Mutant confirmation or mutant validation is the process of re-evaluating mutations in a controlled, replicated environment with sizable sample size. By using this technique, many reported mutants are shown to be fake mutants and keep the real mutants for the next generation. Noticeably, two precautions must be taken while using the procedure because mutant breeding relies on individual plants for selection. The first is to eliminate mechanical mixes, and the second is to prevent outcrossing in the M1 and M2 generations, even in self-pollinated species [9]. The mutant lines with the desired characteristics are selected as a new variety (direct use) or as a parent line (indirect use) for cross-breeding [34]. In more than 210 plant species from more than 70 countries, more than 3200 mutant varieties, including many crops, ornamentals, and trees, have been approved for commercial use [19]. In **Figure 4**, mutant lines that were authorized as commercial varieties were displayed.

To speed up the process of introducing the desired traits into other commercial cultivars, breeders could use molecular markers [35]. Recent improvements in highthroughput mutation detection technologies, such as whole genome sequencing, have increased the effectiveness of detecting the DNA changes that give rise to a new trait. Other efficient high-throughput methods for examination-induced DNA deletions to include reverse genetic techniques, such as Targeting Induced Local Lesions in Genomes (TILLING) has numerous advantages over other reverse genetics techniques because it may be applied to any plant species [36–38]. Also, the mutant or variant allele can be detected and facilely introgressed by applying Genome Wide Association Studies (GWAS) in populations or commercial cultivars [6].

#### **3. A role mutation breeding for intensification of crop production**

Despite the fact that mutation-induced changes could affect any of the 100,000 genes, Micke and Donini [39] emphasized that breeders are only working with a small


#### **Table 1.**

*Officially released mutant varieties in the FAO/IAEA mutant varieties database [19].*

portion of the 100,000 genes of a nuclear genome when two well-established cultivars are crossed. A lack of genetic diversity within and between a species can cause a loss of beneficial characteristics for human beings. If biotic and abiotic stresses occur, the ability of a plant to survive by adapting to these conditions is dependent on the presence of individuals possessing gene alleles that need to adapt to these conditions [26, 40, 41]. Induced mutation has contributed to increasing genetic diversity through the development of new varieties that are more adaptable to climatic changes [34]. Informations in **Table 1** showed the most recent crop varieties that the Mutant Variety Database was registered in 2022.

Changing characteristics to improve production and quality has been the primary goal of mutation-based breeding. Worldwide, induced mutagenesis is utilized in the production of rice (Vietnam, Thailand, China, and the United States), durum wheat (Italy and Bulgaria), barley (Peru and Europe nations), soybeans (Vietnam and China), wheat (China), and leguminous food crops (Pakistan, India). A total of 76 mutant cultivars of 15 different crop species, including barley (5), wheat (5), durum wheat (9), maize (26), sunflower (3), lentil (4), bean (2), pea (1), chickpea and vetch (2), soybean (5), cotton (2), and tobacco have been released in Bulgaria as a result of mutagenesis (2). From 1984 to 2000, several mutant varieties, such as the maize mutant hybrid "Kneja 509" and the durum wheat variety "Gergana," took over up to 50% of the planted area. Over the past 30 years, mutant forms of durum wheat have nearly completely covered all of the growing regions and increased production by twofold [42]. Mutant plants are created because DNA damage is challenging to properly and accurately repair. In general, we use breeding programs to modify crops genetically to produce more, have better nutrition, and be more resistant to biotic and abiotic stressors as well as unfavorable environmental variables [43–45]. In this context, Anter [46] detected that mutant line-2's M 4 generation spikes, as oligogenic trait, were taller than their original parent (**Figure 5**). The top five bread wheat varieties in Egypt were used to develop these lines using the mutagen EMS. He found that mutagen played a central role in the alteration of spike length in the desired direction and an easy to detect in open field. Also, he found that indirect selection for spike length can therefore increasing grain yield because it had correlated with spike weight, grains spike-1, and yield grains spike−1 [47].

*Induced Mutation to Enhance Plant Biodiversity and Genetic Resources for Intensification… DOI: http://dx.doi.org/10.5772/intechopen.108117*

#### **Figure 5.**

*showed spike length of the mutant line-2 on the left side and his parent on the right side in M4.*

Rice seeds of the non-waxy variety "Toyonishiki" turned into the commercial variety Miyuki Mochi, which possesses waxy grains, after being exposed to 20 kK of gamma rays [48]. Two rice mutant lines that can tolerate salt were produced when Song et al. [49] treated commercial cultivar Dongan seeds with gamma-rays: ST-87 and ST-301. Kato et al. [50] were obtained on five high-yielding mutants by 250 Gy gamma radiation treatment of the seeds of five different Japanese rice cultivars. Guo et al. [51] reported that five blast-resistant wheat mutant lines were identified in the M3 generation. A few mutants with resistance were found by Tabinda et al. [52] and could be used in a future breeding program to increase resistance and decrease susceptibility to disease. One of the 139 mutant rice types developed in the United States is "Calrose 76," which was produced using gamma irradiation and officially released in 1977 in California. Through cross-breeding with other varieties, this gene has been transferred, leading to the development of 22 new rice cultivars in Egypt, the United States, and Australia [53].

#### **4. Economic gain of a new mutant variety**

Plant breeders can develop new varieties of rice, barley, sesame, and other crops with higher yields and increased disease resistance by employing the well-known method of mutant breeding. This decreases hunger, stimulates economic expansion, builds new socialites, and generates employment. Furthermore, developing new varieties increases a plant's biodiversity, which increases its resistance to the negative effects of climatic change.

The mutant cultivars increased yield by 20–45% outperforming other crop varieties. In a growing area, these mutant variants are being grown. In Vietnam, formally released 18 mutant rice, including a number of mutant rice cultivars resistant to salinity. The most productive of these saline-tolerant rice varieties were planted by 4.5 million farmers on 30% of the Mekong Delta's rice-producing area, adding an extra \$374 million in income each year. In Peru, mutation breeding techniques


#### **Table 2.**

*Economic gain of a new mutant variety [54].*

produced improved barley mutant varieties that are adaptable to climatic conditions in high altitudes. The mutant barley variety, Centenario II, today yields 3.0 t ha−1, up from 0.8 t ha−1. This variety contributes roughly US \$32 million annually to farmers. Similarly successful is the mutant Amaranth variety, which covers 47.0% of the dedicated area for this crop. Mutant breeding in Indonesia has benefited millions of consumers as well as tens of thousands of farmers. Twenty mutant rice varieties were developed, and one of them is earned a total of USD 2 billion. 10% of the rice types officially registered are mutant varieties [31]. The data in **Table 2** showed that the economic impact of using new mutated varieties.

#### **5. Evaluation standards for mutant varieties**

More than 50 mutant lines have been developed, most of which are rice- and other cereal-based plants. Mutant varieties currently occupy about 15% of the yearly rice production acreage in Vietnam. Mutant lines were created, including 17 different

*Induced Mutation to Enhance Plant Biodiversity and Genetic Resources for Intensification… DOI: http://dx.doi.org/10.5772/intechopen.108117*

varieties of rice, 10 varieties of soybeans, and 2 varieties of maize. The majority of these rice varieties yield substantial amounts of rice, are resistant to pests and diseases, and also produce rice of outstanding quality. More than 50% of the soybean-growing land in Vietnam was occupied by mutant types, contributing to an increase in oil crop production [19]. The following criteria can be used to assess a novel mutant variety.

#### **5.1 Reduced use of pesticides**

Each year, pathogens in agriculture cause major losses in yield, economic output, and ecosystem health. Global disease outbreaks affect the availability of food and lower crop output by 16%. Actual losses from pests (weeds, animal pests, and illnesses) for crops such as sugar beet, barley, soybean, wheat, and cotton ranged from 26–29% to 31–40% [55]. Plant breeders continue to face difficulties with the emergence of new aggressive disease strains, such as the fungus *Puccinia striiformis* that causes wheat yellow rust. Induced mutations have improved a variety of economically significant crops, including wheat, barley, rice, cotton, peanuts, and others. Mutation had a part in the usage of pesticides declining, as a result of the development of new varieties tolerant to biotic stress, which reduces costs and preserves the environment from pesticide overuse [56, 57].

#### **5.2 Increased land use through early maturity**

Mutation breeding was employed in Bangladesh to create 76 early mutant variants across 12 different crop species, facilitating crop rotation. The BINA dham-7 mutant variety, a mature variety with higher cropping intensity, has been cultivated on more than 300,000 acres of land so far. This is because it allows for three cropping seasons annually and alleviates the seasonal food deficit [58]. For peanuts Kale et al. [59] created the TG 26 early maturity variant. In Pakistan, mutant line IAB 78's early maturity, higher yield, and greater adaptability allowed it to eventually cover 80% of the cotton acreage [56].

#### **5.3 Resistant to biotic and abiotic stresses**

Mutation breeding increased the planted area of most crops and, consequently, the revenue of farmers by producing new varieties that are resistant to both biotic and abiotic stresses (**Tables 3** and **4**).

All of these instances demonstrate the expanding influence of mutant breeding in crop production, particularly in the case of rice, which is regarded as the most significant food crop worldwide.

#### **5.4 Improved quality and value of the products**

The increase in quality and nutrition by mutation induction is comparable to increasing agricultural productivity because it is essential to human food. For nutritional and health reasons, it is necessary to enhance the protein and fatty acid profiles, alter the physicochemical characteristics of starch for various end uses, increase phytonutrients in fruits, decrease anti-nutrients in staple foods, and supplement essential minerals and amino acids for humans and animals [74]. Varieties of linseed low linolenic acid products like Linola, created in Australia in 1984, and Solin developed in Canada in 1990, have proved effective. In India, created certain genotypes with less


#### **Table 3.**

*Applications of induced mutagenesis for biotic stress resistance in some crops [34].*


#### **Table 4.**

*Applications of induced mutagenesis for abiotic stress resistance in some crops [34].*


*Induced Mutation to Enhance Plant Biodiversity and Genetic Resources for Intensification… DOI: http://dx.doi.org/10.5772/intechopen.108117*


#### **Table 5.**

*Oil crop varieties with improved character.*

than 1% linolenic acid leads to widespread usage as cooking oil. **Table 5** displayed some successes in improved quality traits from mutation breeding in some oil crops [8].

#### **5.5 Enhancing essential minerals and amino acids**

Quality and nutritious components are equally vital for human meals as agricultural output rises. It is necessary to enhance essential minerals and amino acids for the benefit of both people and animals. For dietary and health-related reasons, protein and fatty acid profiles must be altered. For a number of uses, starch's physicochemical properties must be altered. The induction of mutations that improve the nutritional value of crop plants may be a major goal of induced mutations. The incorporation of numerous mutant genes into commercial crop types has effectively boosted the nutritional value of crops like maize, barley, soybeans, and sunflower [74]. In five rice giant embryo mutants, which are distinguished by enlarged embryos compared to those of the wild type, the amount of protein, vitamin B1, vitamin B2, vitamin E, essential amino acids like arginine, aspartic acid, glutamic acid, lysine, and methionine, as well as mineral elements like calcium, iron, potassium, phosphorus, and zinc, was found to be increased [75]. Increased bioavailability of phosphorus and micronutrient minerals in cereals and legumes has been made possible by the release of new mutant varieties of barley, wheat, rice, and soybean with low phytic acid [74]. Eggum et al. [76] discovered four novel high-lysine barley mutants that had greater protein concentrations, β-glucan, sugar contents, fat contents, and starch contents (Sultan). When compared to "Sultan" (19.7%), the mutants typically had higher levels of dietary fiber.

#### **6. Conclusion**

Crop breeding's objectives in earlier decades included enhanced potential yield, increased and altered oil and protein content, and tolerance to biotic and abiotic stresses [77]. In traditional breeding, we selected plants with desirable traits and culled those with fewer desirable traits. Another technique, known as cross-breeding, involves mating sexually healthy parental lines, whether they are closely or distantly

related, to create new lines that have new forms with desirable traits. On the other hand, encouraging plant mutation will quicken the reproduction process. Mutation breeding techniques can induce site-specific mutations while this is difficult to achieve by conventional breeding techniques [78]. Micke and Donini [39] pointed that breeders are dealing only a few hundred out of 100,000 genes, when two established cultivars are crossed while mutation is induced, may affect any of the 100,000 genes of a nuclear genome. Mutations are the primary source of all genetic variations existing in any organism, including plants [79]. Consequently, the likelihood of finding a novel gene will rise. Understanding mutations and utilizing them has made it possible to increase plant biodiversity and genetic resources for increasing food production in order to counteract climatic changes. Additionally, induced mutagenesis is a safe, effective, and successful method of plant breeding, and the crop varieties it creates considerably improve food security around the world while maximizing plant biodiversity, genetic resources, and the preservation of natural resources. More than 3200 mutant varieties of ornamentals, trees, and crops have been formally released to be used in more than 70 nations. The genetic diversity found within plants' agricultural genetic resources helps to address a number of problems in plant breeding. Since mutations occur at such low frequencies, the discovery of advantageous mutations involves the establishment of very large mutant populations, which has long been a challenge. It is often called the real "art" of mutation breeding to differentiate and select among the a lot of mutated plants those tenuous cases that have developed new desirable traits as generated bythe mutation. Recent improvements in mutation detection technologies have increased the accuracy of identifying DNA mutations that cause a novel characteristic. Molecular markers, such TILLING (targeted induced local lesions in the genome), which allows for the direct determination of mutations in a specific gene, assisted breeders in accelerating the process of combining the desirable traits into an employed variety [19]. At the same time, there are some restrictions on the application mutation breeding such as most of the mutations are lethal, rate is very low, screening is a quite laborious, mostly reversible, mutations mostly are recessive, and the mutations must be induced in gametes to appear [77]. In the coming decades, though, mutations will continue to occupy a place in crop research, particularly for the intensification of crop production to mitigate climate change [77].
