Role and economic importance of crop genetic diversity in food security (2023)

introduction

Biodiversity is the presence of variation between and within the living world for the purpose of improvement, particularly in crops [1]. Biodiversity is necessarily divided into three different main components such as genetic diversity, species diversity and ecosystem diversity [2]. Genetic diversity is the availability of variability of hereditary traits in a population of a given species [3]. Genetic variation is defined as differences in DNA sequence, biochemical traits, physiological and morphological traits such as plant height, flower position, flower color and other distinct features. Ramanatha & Hodgkin, [2] described genetic diversity as the existence of differences in alleles, genotypes, the result of their performance (phenotypes) and the sum total of the genome. The use of genetic diversity is relevant for the further development of cultivated plants [4]. In the presence of low genetic diversity within cultivated species, species are vulnerable to emerging pathogens and other various limitations that lead to productivity losses and this problem leads to a serious decrease in adaptive ranges [5]. Genetic variation is an important driver of evolutionary diversification and a source of phenotypic variation.

The success in plant improvement mainly depends on the broad basis of the degree of genetic divergence [6]. Genetic diversity is of great importance for the development of superior varieties in crop improvement. Superior performance and desirable hybrids are expected when crossing different genetic materials compared to crossing similar genetic materials. The Mahalanobis D2 statistic represents a very successful method based on the analysis of genetic variability, which is a good indicator of genetic diversity. This system must be tested on a large number of cultures to be verified [7]. The improvement potential of crops, determined by the level of genetic diversity present in the crops supplied. Characterization followed by cataloging of the genetic material is an essential requirement for a successful breeding program. Genetic diversity analysis tools are used to measure the degree of genetic divergence between different populations [8]. The presence of genetic variation in plant populations is useful for conservation and breeding programs.

The genetic diversity of plants offers researchers the opportunity to develop new improved varieties with desirable traits that address the preferred traits of farmers and breeders. Crowd techniques are continuously used to assess genetic variability between and within crop populations. These techniques are; (i) morphological characterization or assessment, (ii) biochemistry (allozymes) in the pregenomic era and (iii) analysis of (molecular) DNA markers, particularly single nucleotide polymorphisms (SNPs) in the postgenomic era. The genetic variation of crops can be divided into cultivars between and within a crop. The amount of genetic variation between cultivars is a function of genetic differences between cultivars. Whether natural or human-driven, evolution primarily depends on the genetic diversity that exists in a population. As we know, systematic plant breeding starts with exploiting the natural variation that is available between crops. But over time, genetic variation decreased due to (i) inconsistent breeding practices focused on improving fewer traits (yield and its component traits), (ii) frequent use of fewer selected parents in the variety development program, and (iii) introduction of fewer cultivars, resulting in greater genetic similarity between cultivars of modern crops. The increasing genetic diversity of crops plays a very crucial role in the global food supply to feed the alarmingly growing population [9]. On this day, the genetic diversity of the crop is reduced compared to the previous day for several reasons.

It is crucial to increase crop productivity through proper protection and conservation of crop genetic diversity, and management practices in growing environments need to be changed. Finally, the human population is increasing at an alarming rate and exceeding expected standards of living, which has led to a shortage of natural resources [10]. Therefore, knowledge of genetic variability is the key component in selecting genotypes that resist environmental changes including new pests, diseases and new climatic conditions for the future breeding program. The aim of the article was to understand the role and economic importance of plant genetic diversity for food security.

Concept of diversity and its impact on improving crops

Genetic diversity is defined as the availability of genetic variations that are heritable traits in a population of a given species [3]. For the development of climate-resilient cultivars, the existence of genetic diversity in the form of wild species, related species, breeding lines, and mutant lines is the source of desirable alleles that help plant breeders [10]. Genetic diversity is the natural endowment that has arisen through mutation, hybridization of gene flow, and polyploidy of genetic material. Genetic variation is allelic differences of genes in DNA or RNA arrangements in a population's gene pool. Genetic diversity is the broader term that encompasses all existing variations between different genetic materials in relation to the genetic composition of crop species. There are three levels of biodiversity categories. They are: Ecosystem diversity, which represents the variability between different species communities in the highest hierarchy. The second level of biodiversity is species diversity, which indicates the different species within a community, and the third biodiversity is genetic diversity, which is the diversity that is present in different varieties of species.

Genetic diversity plays a significant role in ensuring food security by increasing farmers' income and plays a role in current and future food production [11]. The importance of plant genetic diversity is very great, especially since the dawn of agriculture, natural genetic variability in crop species has been exploited to meet food needs for subsistence and is now focused on food surplus for growing populations. Current plant gene banks have emerged in response to two distinct purposes: first, the mobilization, management, and long-term storage of materials that can be readily used in plant variety improvement programs, and second, the maintenance of long-term improvement in plant genetic diversity. , for the potential future use of mankind. Agricultural genetic resources are the basis of agricultural production and significant economic benefits result from their conservation and use. Genetic resources provide the basic mechanisms that allow plants to convert soil, water and sunlight into something of crucial human nutritional value. The diverse genetic resources allow humans to select and cultivate plants with desired traits, thereby increasing agricultural productivity. Genetic diversity is the backbone of a nation's food security and the foundation of overall economic development.

Benefits of genetic diversity

Genetic diversity is the basis for the improvement of crops and the existence of plants in nature. It is clear that genetic diversity offers opportunities for breeding varieties with desired traits, consisting of both breeder-preferred traits and breeder-preferred traits. To meet subsistence food needs, genetic variability was exploited in early agriculture. Currently, the development of climate-adapted cultivars is up to the plant breeder as climate components vary and affect the normal growth and development of crops. The availability of genetic diversity is directly related to the presence of desired alleles and helps to develop climate resilient cultivars. The sustainability of agricultural production and food security are threatened by the increasing unpredictability and severity of water stress due to global climate change. Incorporating adapted natural genetic variation into breeding programs can enrich current genetic diversity for stress tolerance and improve yield under stress. Genetic diversity allows for the development of high yielding, better quality varieties favored by farmers and breeders. Genetic diversity also plays a key role in developing potential strains to resist new diseases, insect pests, extreme heat and extreme cold. Genetic diversity facilitates the development of varieties for specific traits, such as B. Tolerance to abiotic and biotic stress and improved quality. The Food and Agriculture Organization of the United Nations has identified the decline in genetic diversity as the most serious environmental problem [12]. In general, genetic diversity, strictly speaking, is the amount of genetic variation available between plant species [13].

variability and adaptability

The greater genetic variation of crop species offers greater opportunities for improvement to adapt to environmental conditions. Adaptability is the best survival of a genotype against a given environment. Adaptation to climate variability is a very critical issue in the food security discourse. Many factors are involved in crop adaptation and the range of conditions includes edaphic, environmental and biotic factors. The phenotype is the result of genotypes, environment and interaction of genotypes and environment [14]. Genotype-environment interaction is a prerequisite for crop improvement and evaluates the genotypes improved in multiple environments. The interaction between genotype and environment leads to unstable performances between genotypes in different environments. Crop growth and development are influenced by a complex interplay of environmental (E) and management (M) factors [15]. The breeding program must tightly control the intensity of selection during breeding, as genetic diversity is the essential basis for long-term genetic gain. Adaptability essentially depends on the availability of genetic variability within and between crop species.

Factors affecting genetic diversity

Genetic diversity is influenced by many different factors. There are evolutionary forces that continually alter the genetic abundances of crop species that affect the genetic diversity of a population. Selection, mutation, gene flow, and gene drift are the evolutionary forces that affect the gene pool of a given population. Genetic diversity is caused by several factors. Some of them are mentioned here:

Evolution:The term agricultural evolution summarizes the changes in crop plants over time due to natural and artificial selection and modern breeding methods [16]. Evolution began in the wild and went through various processes to produce the desired domesticated ones. Evolution is a gradual change that has produced the plant diversity of today from the first and most primitive organisms [17]. Evolution, through gradual processes, leads to the transformation of genetic diversity that eventually led to the new cultivated species. The theory of evolution developed by Charles Darwin since 1859 dictates that there is variation in the initial plant population and the best adapted individuals survive and reproduce in larger numbers over time [18]. In fact, domesticated plants provide alternative materials for evolutionary genetics in the development of genome architecture [19].

domestication:In domestication, desirable traits are selected while other undesirable traits are neglected, resulting in a reduced frequency of ignored alleles. Domestication is the conversion of wild ancestors into cultivated species through continuous selection of desirable traits from cultivated plants to meet human demand [16]. Domesticated plants in various agroecological settings around the world for the various desirable traits demanded by breeders. Domestication is about the artificial selection of crops with desired traits to ensure food and food security [20]. There is genetic modification of morphological and agronomic traits in domestication processes to adapt crops [21]. McCouch [22] pointed out that domestication is about adapting high-yielding varieties with resistance to biotic and abiotic stress, improved nutritional quality, large seed and fruit size, non-breaking, reduced seed dispersal mechanisms, more compact growth habit, early-harvesting plants. In the course of domestication, wild plants developed into useful plants through artificial selection in order to meet specific human needs. The artificial selection of crop plants causes a change to transform wild species into domesticated ones [23].

Plant improvement:Plant breeding has a profound impact on food production and will continue to play a crucial role in global food security. Genetic diversity plays a crucial role in crop improvement, as crossbreeding between genetic material from different origins demonstrates superiority over closely related species. Plant breeding depends primarily on the existence of significant genetic variation in order to achieve the maximum genetic yield potential of crops and the exploitation of this variation through effective selection for breeding [24]. Therefore, plant breeding was earlier started with the domestication of plants to develop superior genotypes in terms of yield, disease and insect resistance and many other different traits [25]. Plant breeding has reduced variation in genetic materials due to crop plants' limited preferences for further enhancement of various desirable traits.

Mutation:Mutations are the original source of genetic variation and primarily create genetic diversity. Mutations can have positive, neutral and negative effects on the genetic modification of crop species. Mutation is the sudden heritable change in genetic diversity that occasionally occurs through the aberration of genetic material such as DNA, RNA, and proteins in cells. Mutation plays a large role in increasing genetic diversity to feed the growing human population [26]. Mutation is the main reason for changing genetic diversity. Genetic diversity is the variation that occurs in genetic information that depends on the frequency and variety of alleles in individuals of a population or species. Mutation is the driving force behind the creation of sustainable genetic diversity that can be used for further improvement. Induced mutagenesis expands genetic variation, while traditional breeding approaches constrain genetic variability for improvement over time. The use of mutational breeding creates significant genetic diversity in crops through crop improvement to improve community livelihoods [27].

Migration:Migration is the movement of crop plants between and within a species. It occurs directly through the dispersal of seeds and pollen, vegetative reproductive organs such as suckers, rhizomes, in species capable of vegetative reproduction. On the other hand, migration is about gene flow that occurs through movement from one area to another and results from the mixing of two or more genes from the population through pollen and seed dispersal.

Selection:The selection of plants from a population is almost always based on their phenotype, and the phenotype has both hereditary and non-hereditary components. Genetic improvement of crops depends on the quality and extent of genetic variability available in the population and on the nature of the relationship between productivity and its components. This enables the simultaneous selection of many yield-relevant characteristics [28]. Adequate variability provides options from which to choose for improvement and possible hybridization.

Effects of genetic erosion

Genetic erosion is the depletion of genetic variability due to various factors over a period of time in a specific location. The loss can involve single genes or a combination of genes. Genetic loss is the reduction in genetic diversity over time [29]. Genetic losses mainly caused by modernization of agriculture, where native varieties are replaced by new improved varieties. The loss of genetic variation is becoming a bottleneck in plant breeding. Genetic loss can occur at three different levels: culture, variety, and allele. Climate change, deforestation, environmental degradation, urbanization, displacement of local landraces are the main causes of genetic loss. There are three different methods to quantify genetic loss: (1) Genetic erosion as the complete loss of a crop, cultivar or allele [30]. (2) Genetic Erosion as Facilitation of Wealth [31]. (3) Genetic erosion to facilitate uniformity [32]. Genetic loss as depletion of justice follows from the indicators of variability used in population genetics such as the Shannon index [33] and the Nei index of genetic diversity [34]. Genetic diversity is measured by the frequency of genes within a group of genotypes in a given region. The degree of diversity is reduced by dominant single genotypes or alleles. Genetic loss in ex situ conservation can occur due to gene depletion resulting from regeneration and storage practices [35].

Narrowing down the genetic basis of crops

The narrowing of the genetic base of crop plants is becoming a serious problem in the development of new and superior cultivars with useful traits. The depletion of genetic variation means not only the replacement of a variety of landraces with one or a few modern varieties, but also with the loss of farmers' native knowledge and ability to manage their own plant genetic resources. A narrow genetic base is very problematic in modern agriculture due to the selection of the best performing varieties with preferred traits. The main reason for the narrow genetic base is the crowding out of the diversity of terrestrial races by a few modern varieties. Genetic erosion adversely affects development when the loss of genetic diversity severely narrows the genetic base of modern crop varieties [36]. Narrow genetic base is defined as a loss of genetic diversity and generally refers to a reduction in the number of specimens of a species [37,38]. The green revolution was the transition from growing landraces to modern varieties to increase agricultural productivity through improved varieties, excessive agricultural inputs, and mechanized farming. One of the most important reasons is the replacement of landraces, which have been developed and genetically improved by traditional farmers, but have not been influenced by modern breeding practices or traditional varieties, with modern varieties or high-yielding varieties. Creole cultivars from a primary center of origin are believed to contain many valuable genes, particularly for resistance or tolerance to various biotic and abiotic stresses, and are therefore promising for their use in future plant breeding programs. The term genetic erosion is sometimes used narrowly to mean the loss of genes or alleles, and more broadly the loss of cultivars. There are several ways to present the problems of genetic erosion. One of the most useful indicators is the narrowness of the food base. The narrow genetic basis is the reduction in population variation due to inbreeding and genetic drift, which largely causes the danger of small isolated populations. The narrowing of genetic diversity can lead to the complete loss of cultivated plants.

Conclusion

Genetic diversity is the amount of genetic variation available between crop species for use in the breeding program. Having sufficient genetic variation is key to a successful breeding program. Genetic diversity is paramount in developing superior cultivars in terms of productivity and other desirable traits. It is also very crucial in producing superior hybrids and desirable recombinants. Genetic diversity determines the efficiency and effectiveness of breeding, which can lead to increased food production. From the point of view of plant breeding, the classification of genetic variability into the respective heterotic group is fundamental for the development of vigorous and differentiated hybrids with regard to economically important traits. Genetic diversity provides other natures with vital protection against climate change, pests and diseases.

Creating enough genetic variation to enhance the golden crop becomes a challenge to further improve genetic yield potential. Currently, plant breeders use genetic material without knowing their genetic background, such as B. unadapted exotics, adapted exotics, and existing genetic material as a source of new alleles that protect and enhance genetic gain through selection. Genetic diversity makes a very important contribution to ensuring food and nutrition security. Knowledge of the genetic diversity of genetic material is very crucial for crop improvement. Effective selection is extremely important in any crop improvement when sufficient genetic variation is available for different traits. Analysis of the genetic variability of cultivars for different agronomic and morphological traits is very crucial in order to offer the possibility to select a number of promising cultivars. Genetic variation is the fundamental basis for the continuous development of new superior strains. Therefore, characterization of genetic material using different statistical tools is crucial in crop improvement program. The improvement of qualitative and quantitative traits mainly depends on genetic diversity.

In general, plant breeding depends primarily on the existence of significant genetic variation in order to achieve the maximum genetic yield potential of crops and the exploitation of this variation through effective selection for breeding. The availability of genetic variation is a key requirement for successful plant breeding. Plant breeding focuses on creating genetic variation and applying appropriate selection techniques to improve quantitative and qualitative traits. Sufficient genetic variation provides alternatives from which to make selections to improve crops. Phenotypic expression is the result of genotype, environment, and genotype-environment interaction, and production is the result of several different factors. Genetic variability that decides the fate of an effective plant breeding program. The existence of enormous genetic variation and efficient selection are two essential prerequisites in plant breeding. There is an opportunity to expand genetic variability by using related wild species in conventional crosses, while new genetic traits can be obtained through induced mutation. Improving crops is an imperative process to cope with increases in human population and climate. Success in plant improvement depends on the amount of genetic variation present in the genetic materials and the selection of genetically superior genotypes.