Revolution in Plant Genetic Resources

Abstract

Plant genetic resources are the use of plant materials, such as seed, pollen, and other plant organs, which have potential value for food and agriculture. The future of crop improvement programs relies on the quality of plant materials. Globally, agriculture and food production are confronted with diverse issues, such as climate change, genetic erosion, land degradation, loss of biodiversity, and human encroachment. A wider genetic diversity research will mitigate these challenges and improve crop production. In today’s science innovative approaches, such as the use of molecular markers, cryopreservation, genebanks, and relevant molecular assays are changing the face of collating data, preparation, processing, and sorting of genetic resources. The objective of this review article is to discuss the revolutionary approaches to plant genetic resources and how they will help in the improvement of agricultural production.

1. Introduction

Plant genetic resources date to about 10,000 years ago when man invented agriculture. People started differentiating variations in plants and later domesticated them through natural means of selection [1]. These plants became our foremost crops. Our planet houses around 310,000 described species of plants and possibly an overall estimate of 400,000 species. About 5000 plants have been harnessed by modern man for food, clothes, shelter, and other needs. And as our population increases, we become increasingly dependent on plants for survival. Today about 150 plant species are what humans dearly need for food and essential needs with only about 12 of those plants proving 80% of the world’s food. Some of them are wheat, rice, barley, oats, millet, cotton seed, potato, cassava, yam, soybean, common beans, tomatoes, onion, sugarcane, melon, banana, and others [2].

This diversity of species is concentrated into areas of unusual richness and exhibits variation at both a global and a regional scale. The taxonomic diversity of plants is usually highest in the tropic with high amount of rainfall. The species found in one habitat can be used to identify the characteristics of the conservation priorities of that habitat which also mirrors the uniqueness of the ecosystem. For us to achieve measurable progress, a range of actors will need to generate, access, integrate, and synthesize data that is widely dispersed across organizational and international boundaries, and work through international partnerships that bring together complex portfolios of skills, sources of information, and perspectives [3, 4].

Over the years, plant conservation has often been reduced to an activity for government agencies involved in forestry management. Halewood et al. [3], outlined the benefits of establishing a conservation center for plants. They include promoting an integrated approach to plant conservation; utilizing and promoting professional skills; developing collaborative relationships with protected area networks, government agencies, parastatals; and the omics revolution in the biological sciences has considerable potential for changing the flows of information, the nature of partnerships, and the range of products that can be generated through plant genetic resource conservation.

In germplasm conservation, the method of collection initially captures maximum variation of plant materials. This procedure can be carried out either in the wild or controlled environment [5]. Ex situ conservation is reliable usually in seed banks, where they are cryopreserved. Additionally, technologies for generating and analyzing large quantities of genotypic, phenotypic, and environmental data are evolving at accelerating rates, so too are technologies and methods for synthesizing genetic materials [6].

2. Utilization of plant genetic resources in food sustainability

The sustainable use of genetic resources is critical to food security and sustainability. Globally, the improvement of food production has been successful. However, biodiversity seems to have been neglected. Biodiversity influences food production, as it ensures adequate and quality soil for optimum productivity and supplies invaluable genetic resources for all crops [7].

The world has been struggling to provide quality nutrition and access to safe water and eradicating all forms of malnutrition according to the sustainable millennium goals (SDGs). In 2020, an estimated 811 million people faced hunger attributed majorly to COVID-19 pandemic. Another report predicted that if global food security is not treated as a matter of urgency an additional 660 million people may suffer from hunger by 2030 [8].

Humans’ inalienable rights would be realized when there is enough food for sustenance. From a broader aspect, it is pertinent for countries to provide access or means to sufficient food and potable water for their citizens. Great strides need to be shown in boosting food production, providing genetic resources, and widening the biodiversity of food crops. Government needs to enact favorable laws and policies and create solid institutional framework to ensure the access to genetic resources and agricultural materials. As no country can adequately sustain food production without a robust and sustainable genetic resource [8].

Molecular tools have proven to overcome some of the bottlenecks experienced in agriculture. Molecular techniques have continued to answer previously unanswered questions in taxonomy, breeding, etc. Techniques, such as the use of microsatellites and single nucleotide polymorphism (SNP), amplified fragment length polymorphism (AFLP), and random amplified polymorphic DNA (RAPD) are efficiently used in diversity study and in pest and disease resistance, high yield and salt and drought tolerance breeding programs [9, 10].

3. Biodiversity of plant genetic resources

Biodiversity is the bedrock of food security. The purpose of sustaining a functional biodiversity is to downgrade the threat of genetic erosion of important genetic resources. The protection of our biodiversity is critical as it directly affects food security. Plant genetic resources are at perennial risk of genetic erosion, which leads to loss of valuable genes, concomitantly loss of biodiversity. Some of the elements responsible for loss of biodiversity include climate change, floods, droughts, fire hazards, and urbanization to mention a few [11, 12].

The necessary practices for protecting targeted plant genetic resources, some of which may be harvested for food, in nature are locating the species, describing the status of their conservation, and actively managing and monitoring the populations where they occur in nature [13]. This is particularly critical as the genetic diversity of PGRFA in nature is being eroded by various factors, that is, loss and fragmentation of habitats and extreme weather events that may be linked to climate change [13].

Genetic erosion of plant genetic resources has been problematic both for primordial and modern agriculture and has been broadly documented. Several issues highlighted above, such as natural and man-made disasters are largely responsible for this immense loss. China in 1949 recorded a loss of about 10,000 wheat varieties; the USA in the 1970s lost about 95% of cabbage, 91% of maize, and 81% of tomatoes all to genetic erosion. It is noteworthy to mention that the cultivation of high-yielding variety causes genetic uniformity and is a pointer to the spread of diseases. This has been reported in wine grape and corn blight by the Information Bulletin, ICSC II, 1996.

4. Conventional approach to conservation

Before technological approaches to conservation were birthed, humans were conservation inclined. There has always been a need to preserve food materials for commercial purposes and to ensure their continual survival. Msuya and Kideghesho [14], outlined nine traditional conservation practices by the locals for medicinal plants. They include domestication, beliefs in sacred forests, beliefs in sacredness of trees, respect for cultural forests, protection of plants at burial rites, selective harvesting, secrecy, use of energy-saving traditional stoves, and collection of deadwood for firewood. The setbacks in these crude practices were climatic factors, pests and diseases, poverty, development activities, and changing agricultural policies. Traditional approaches are not sustainable and cannot meet our ever-growing population. Genetic erosion and poor management are factors delimitating traditional crops [15].

5. Advances in plant genetic resources

The conservation and use of plant genetic resources are important to the continued maintenance and improvement of agricultural and forestry production and, thus, to sustainable development and poverty alleviation. The objective of plant genetic resources conservation is to preserve as broad a sample of the extant genetic diversity of target species as is scientifically and economically feasible, including currently recognized genes, traits, and genotypes [16].

Germplasm banks are storage repositories equipped with facilities for long time storage. Some facilities have capacity to store genetic materials for 25 years and more. The brain behind conservation of plant genetic resources is to have a lot of variation. Variation in genetic resources affords farmers and researchers with options for breeding and other programs. Diversity of both landraces and introduced varieties ensure that the food global basket is never empty [12, 17].

Molecular and in vitro culture techniques are great tools. In vitro culture such as tissue culture provides multiplication of plantlets or clones of endangered plants. Tissue culture generates plant free from viruses, bacteria, or fungi. Molecular markers have been deployed in diversity study and for generating data for plant fingerprint. They are used to identify cultivars or landraces; used to discover important genes of interest and characterization of species [5]

The integration of big data into breeding programs is revolutionary. Generating sequence information is no longer a bottleneck to crop improvement. Phenotypic characterization has historically been more problematic, but increasingly, molecular phenotypes can be used as indicators of physiological or performance phenotypes, while quantitative imaging techniques using remote sensing can directly measure plant architectural and stress response characteristics in a variety of experimental set-ups [18].

6. Biotechnological approach

In modern agriculture, improved crops are farmers’ preferred choice. Crops with improved yield ability, resistance to pests and diseases, and reduced environmental impacts are usually desirable. These are achievable with traditional methods but can be improved and enhanced using biotechnological approaches. The approach is genetically fingerprinting varieties from the wild and landraces. These plants are sequenced, which enables researchers to know which genes are important in conferring the trait that is needed. Utilization of these genes for agricultural purpose is a huge task because it involves a lot of data that the bioinformaticians need to deal with. This computational approach will be used to collect data from plants in gene banks and analyze promising plants for further analysis [19].

In an ever-growing population, to meet food demand, a sustainable system for food production is necessary. A very exquisite technique is the use of in vitro culture and cryopreservation, which is making it easy to conserve genetic resources especially seeds since most are difficult to conserve. Also, techniques such as enzyme-linked immunosorbent assay (ELISA) is used in testing healthy seeds against pathogens. Another method is tissue culture, used for eliminating systemic diseases like viruses for germplasm conservation. Polymerase chain reaction (PCR) and other molecular approaches are proving useful improvements in collection, accessioning, and resolving taxonomic discrepancies in relationship [19].

Molecular techniques are continuously evolving and their application in determining variation has been successfully applied in plant breeding. Molecular techniques for detecting variation include restriction fragment length polymorphism (RFLP), use for cutting short sequences of interest, and the use of PCR-based techniques such as amplified fragment length polymorphism; random amplified polymorphic DNA and simple sequence repeats have also proved very effective on genetic diversity study. These are all used to improve the state of plant genetic resources [19].

7. Cryopreservation

Cryopreservation is the storage of plant materials at ultra-low temperatures in liquid nitrogen (-196^oC). The plant cells kept at this low temperature are devoid of metabolic activities and cell division. Therefore, the materials can be kept or stored for long time without any changes in their cellular structure [20].

Cryopreservation can be a primary or secondary storage technique. For certain plant materials such as embryonic culture that lose their capacity to move to the next stage of embryo formation, it could be a form of primary storage. When used for the conservation of plant genetic resources, it is a secondary storage form and usually as a form of backup or reserve for plant species [21]. The prospect of cryogenic technology is promising as it is important in conservation of genetic uniformity, preservation of rare genomes, sustaining disease-free plant materials, maintenance of morphogenetic potentials, and delaying aging of plant materials. The above techniques are all forms of secondary storage, which have tremendous commercial benefits [19, 21].

8. The evolution of genebanks

The erosion of genetic diversity of plant species is a global concern and a threat to food security. This has continued to stretch the stability of agriculture globally and negatively impacted market demand. The creation of genebanks in the 20th century was strategic and a recovery move to conserve local varieties (landraces). Ever since its creation, there have been some bottlenecks limiting the progress [22], outlined the outcome of the genebank workshop held in Spain in 2014. At the workshop, stakeholders summarized some of the shortcomings of genebanks since their creation. They include inefficient coordination of species across genebanks; insufficient phenotyping, genotyping, and epiphenotyping; and noticing unnoticed duplicates and lack of enough funding among other challenges outlined.

Today, there are about 1750 genebanks in the world housing millions of plant accessions and their wild relatives. Globally about 7.4 million plant accessions are banked ex situ in over 1750 genebank facilities. In conservation and utilization of crop diversity, genebanks are invaluable. It supports germplasm exchange, international ex situ collections, mining of genetic resources, and safeguarding of distinct species [23, 24].

9. Integration of farmers

The variation of crops has multifaceted impact on farmers as it influences their choice. Farmers’ choices are influenced by certain traits, such as high yield, pest and disease resistance, nutritional values, and processing and taste qualities. However, due to poor and scanty research, farmers are usually left with their local varieties, which they continue to cycle for years. Consequently, militating their production in general [25, 26].

Primarily, the benefits of preserving plant genetic resources in genebanks are to assist farmers, especially rural farmers. Farmers need to work with plant genetic experts in choosing crop reproduction systems, cycle time of landraces, and genotype and phenotype characterization [25].

Many farmers are presently left with little option to practice modern agriculture both as a way of life and a form of social interaction. Farmers have been indirectly forced onto the global mono-cultural system of industrial agriculture, as evidentin their neglect of the traditional landraces, because of radically shrinking space for their (farmers’) relevance and operation in the global food system. It has become very necessary moving forward for farmers to be schooled on genetic diversity of crops. The loss of potential of invaluable resources is hampering development of agriculture, especially in third-world countries. If plant genetic resources are well managed by all stakeholders, it will help reduce the high cost of food, reduce the cost of production, and improve both farmers and society at large [26, 27, 28, 29].

10. Conservation strategy

The initiation of programs to study modern germplasm conservation strategy has been instituted in many international bioscience centers. This has been prompted by the loss of plant genetic resources [20]. Currently, biodiversity is currently being lost at up to 1,000 times the natural rate. Some scientists and researchers are now referring to the crisis as the “Earth’s sixth mass extinction,” comparable to the last great extinction crisis 65 million years ago. These extinctions are irreversible and present a serious threat to our health. Identification and management of protected areas is the pivot of biodiversity conservation. We must ensure that collection methods are able to capture most variation and also techniques that reduce genetic erosion [20, 30].

The use of in situ and ex situ methods in conservation of plant genetic resources have been widely used. In situ techniques have been successfully used in collecting small zygotic embryos and taking them back in sterile state to the research laboratories. Samples are preserved and remain in good condition afterward. Ex situ methods like storage of seeds, the use of botanical gardens, and genebanks have recorded huge success in the conservation of plant genetic resources, especially in tree crops. Crops like banana, cassava, potato, and yam that do not easily produce seeds are better to conserve in field genebanks. For the sake of loss of information or sample identity, it is better to conserve duplicate samples to avoid total loss in event of calamity or destruction (Withers and [20, 31, 32]).

Human activities have continued to threaten the survival of our biodiversity. This continued pressure has resulted in rise in the number of species under threat. Factors, such as weed infestation and introduction of new species have been implicated in narrowing plant diversity. Urbanization and globalization are other technical factors threatening conservation of plant genetic resources with orphan crops being the hardest hit. We must be proactive in our approach to preserve our biodiversity, because biodiversity is an important factor for food security [5, 33].

11. Discussion and conclusion

We live in a technologically advancing world that is having significant impact on the conservation of plant genetic resources. Concerns in agriculture about the loss of genetic resources and loss of genetic diversity propelled the response from scientists globally. This necessitated the use of advance technology. The use of advance biotechnological techniques, such as molecular marker technology, enzyme assays, cryopreservation, and modern genebanks have recorded huge success.

No concept is universally correct, and more than one may be appropriate in any context [34], underscoring the need for plant geneticists and crop scientists to work together. As there is need to study, understand, and enhance the value of plant genetic resources through research. For a successful collaboration, there is need to understand the full extent of plant diversity and analysis of the best technological approach to adopt in conserving plant genetic resources [11]. This collaboration should also be extended between Africa and the international community as much of Africa’s biodiversity is still understudied.

The use of modern techniques in plant genetic resources especially biotechnological techniques, genebank, and cryopreservation methods have been highly beneficial in improving conservation and management of plant genetic resources. Areas, such as diversity gap data, gene pool coverage,

and molecular markers technology are vital in advancing the science of how plant genetic resources can be properly managed [20]. This review article recommends a sustained and proactive strategy in sharing genetic diversity data among scientists and the integration of farmers into global network of food security. It is important to add vital plant biological information, such as genotypic, phenotypic, and epigenetics data into the database for easy access and traceability. Farmers should be able to access this information with ease too. Additionally, empowering local farmers with requisite biotechnological tools and knowledge and other advanced methods of conserving plant genetic resources will go a long way in sustaining global efforts on food security [16, 26, 28, 32, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47].