Genetic diversity in the agricultural system is recognised as the foundation on which food, livelihoods and income security are based. It is the result of a natural selection processes and the careful selection and inventive developments of farmers. Many farmers, especially those in environments where intensive agriculture cannot be practiced, rely on a wide range of crop and livestock types. This helps them maintain their livelihoods in the face of sub optimal soils, biotic and abiotic stress like disease and uncertain rainfall, fluctuation in the price of cash crops and socio-political upheaval.
Many minor or underutilised crops are frequently found in proximity of the main staple or cash crops. Yet they are neglected and little effort is made to either conserve them or mainstream them for domestic use or the market. During times of stress like drought or flood such under utilised plants can play an important role in food production systems at the local level. Plants that will grow in degraded soils and livestock that will survive on little fodder are crucial to the survival strategies of communities that live in marginal areas.
In agriculture and forestry, genetic diversity can enhance production in all agricultural and ecosystem zones. Several varieties can be planted in the same field to minimise crop failure and new varieties can be bred to maximise production or adapt to adverse or changing conditions.
Newer strategies for stabilising production involve the use of varietal blends (a mix of strains sharing similar traits but based on different parents) or multilines (varieties containing several different sources of resistance). In each case, the crop represents a genetically diverse array that can better withstand disease and pests. Despite these efforts, genetic uniformity still places some crops at risk of disease outbreaks, and in some regions that risk is considerable. Some 62 per cent of rice varieties in Bangladesh, 74 per cent in Indonesia and 75 per cent in Sri Lanka are derived from one maternal parent. In the United States, from 1930 to 980, the use of genetic diversity by plant breeders, accounted for at least half of the doubling in yields of rice, barley, soybeans, wheat, cotton, and sugarcane; a threefold increase in tomato yields; and a fourfold increase in yields of corn, sorghum, and potato.
As important as genetic diversity is to increasing yields, it is at least as important in maintaining existing productivity. Introducing genetic resistance to certain insect pests can increase crop yields but since natural selection often helps insects quickly overcome this resistance, new genetic resistance has to be periodically introduced into the crop just to sustain higher productivity. Pesticides are also overcome by evolution, so another important agricultural use of genetic diversity is to offset productivity losses from pesticide resistance.
Wild relatives of crops have contributed significantly to agriculture, particularly in disease resistance. Thanks to wild wheat varieties, domesticated wheat now resists fungal diseases, drought, winter cold and heat. Rice gets its resistance to two of Asia’s four main rice diseases from a single sample of rice from central India, Oryza nivara.
Genetic diversity and livestock breeding
Genetic diversity is becoming increasingly important in forestry and fisheries and the use of genetic resources in livestock breeding has markedly increased yields. The average milk yield of cows in the United States has doubled over the past 30 years and genetic improvement accounts for more than 25 per cent of this gain in at least one breed. Although not as dramatic, Asia has also seen a rise in milk output due to the improved genetic stock of dairy cattle.
For a variety of reasons, genetic diversity has been less useful in livestock breeding than in crop breeding. Whereas one major use of the genetic diversity of crops has been in the development of strains resistant to specific pests and diseases, livestock husbandry has relied largely on vaccines since animals (unlike plants) can develop immunity to disease. Also, maintaining livestock germplasm is tougher logistically than maintaining the genetic material of plants: since animals do not produce anything comparable to plant seeds that can be stored easily. An additional problem is that many of the closest relatives of domesticated animals are extinct, endangered or rare, and thus unavailable for breeding. This should be a priority area for germplasm conservation.
In Cameroon, at least four breeds of domestic fowl are kept in a free range system in villages. Indigenous fowl are kept for food and income generation, for ritualistic and cultural reasons, for sport, as breeding stock and for traditional medicine. In Mexico, farm women keep up to nine breeds of traditional fowl, as well as local and exotic breeds of turkey, duck and broilers in their back gardens. In selecting the best breeds, they consider as many as 11 different characteristics, including egg production, market value, appearance, heat and cold tolerance, growth rate and feeding habits. On this ranking, the most preferred birds are indigenous turkeys and ducks.
Intra species diversity is known to be rich in domesticated crop species and breeds of livestock. The inherent variation within farmers’ varieties and landraces is immense for cross-pollinated species as maize. For self-pollinated crops such as rice and barley and for vegetatively propagated crops like potatoes and bananas, intra species variability may be low but the number of landraces developed may be very high. Estimates of the number of varieties of Asian rice (Oryza sativa) are varied but range from several thousands to more than 100,000. In the Andes some communities grow as many as 178 locally named potato varieties. The FAO has compiled the genetic variation available in crop varieties and their contribution to food and livelihood security.
Pastoralists and livestock keepers have also generated and safeguarded considerable diversity within breeds through their animal husbandry. India alone has 26 different breeds of cattle and eight breeds of buffalo, 42 breeds of sheep and 20 breeds of goat in addition to eight breeds of camel, six breeds of horses, 17 breeds of domestic fowl, and a number of native pigs, mithun and yak. Worldwide, the total number of mammalian and avian livestock breeds in use is thought to be between 4,000 and 5,000.
Agricultural biodiversity also plays an important role in high input farming based on the use of high yielding varieties. This biodiversity helps sustain many production functions such as organic matter decomposition and humus building and pest control as well as pollination. In countries like the US or Australia, farmers in orchards manage cover crops primarily to save soil and water. Usually though, the species chosen will usually perform other functions in the agroecosystem. In addition to protecting against soil erosion, cover crops usually enhance soil structure, improve soil fertility and aid nutrient cycling. They also provide habitat heterogeneity and thus support a favourable balance between pests and predators, which helps in pest management. Depending on the species, trees can also provide fodder for animals, thus increasing the number of internal linkages within the agro ecosystem. The efficient working of such systems is dependent on the diversity available within all the parts of the agro ecosystem.
Studies comparing the soil biodiversity in biodynamic, organic and conventional farms show higher species diversity and functional levels in biodynamic and organic plots than in conventional systems. The significantly higher biomass, diversity and functional activity of soil microorganisms, earthworms, ground beetles and spiders found in biological systems are largely due to the organic inputs and more selective plant protection measures used in the biological systems.
In high input-high output agriculture, microbial diversity is also central to integrated plant nutrition systems (IPNS) that aim to maximise the plant nutrients available to crops, by complementing the use of on-and off-farm sources of plant nutrients. Nitrogen fixation through bacteria (Rhizobia spp) and algae (Azolla spp) as well as phosphorus cycling via mycorrhizal fungi species are particularly effective. Microbial diversity is generally known to mediate nutrient cycling and its role in crop production must be better acknowledged in planning for higher productivity.
Yet another role of agrobiodiversity is in pest control. Agricultural biodiversity in the form of insects, nematodes and micro-organisms play a key role in controlling agricultural pests and diseases. More than 90 per cent of potential crop insect pests is controlled by natural enemies that live in the grounds adjacent to farmlands. Failure to use the advantage comes with a heavy cost. The cost of using chemical pesticides in place of natural pest control was estimated at $54 billion per year in 1999 by FAO.
Both modern and traditional methods of pest control are based on biodiversity. Crop varieties and animal breeds resistant to specific pests and diseases are bred using the genetic diversity available in situ and in ex situ collections of germplasm. In both temperate and tropical agroecosystems, using varietal mixtures can be effective in containing pests and diseases in cereal crops as well as in cassava and potato. Many studies show that insect pests tend to be less abundant and do less damage in agroecosystems with higher plant diversity such as intercrops, polycultures, crop rotations, cover crops, mixtures of annual and perennial plants and agroforestry. Plant diversity in the field acts to reduce pest damage by interfering with host preference and reproductive behaviour. The latter works by enhancing the pests’ natural enemy populations. Rich and diverse flora within and around agroecosystems can promote biological control or confer an overall resistance to pests and disease outbreaks.
Understanding how agricultural biodiversity affects pest and disease dynamics directly or indirectly is critical for developing pest management strategies. Work in rice fields in Indonesia shows that there is an enormous diversity of arthropods, even in intensive agriculture systems. Microorganisms like bacteria and phytoplankton and humus feeding insects spring to life as soon as fields are watered. This provides abundant sources of food for predators, which results in high pest mortality from the start; thus minimising the chance of damaging pest outbreaks. However, the strength and stability of the rice agroecosystem is influenced by two main external factors:
1. Regional and local pattern of pesticide use.
2. Landscape effects, like whether fields are synchronously planted, the duration of fallow periods, degree of natural vegetation and presence of water bodies or other sanctuaries for natural enemies.
Such information on the agrobiodiversity, in and around rice paddies, provides the ecological basis for integrated pest control through management of the wider landscape leading to decisions on the use of pest control agents.
The richness in the diversity of pollinating agents will determine the output of several crops. Pollination mediated by the diversity of pollinators like bees, birds, butterflies, bats and such like is an important function in terrestrial agroecosystems but not so much in aquatic ones. Nearly half of all plants, including food-producing species, are pollinated by animals and insects. For example, the pollination of various fruit crops by bees and other insects is critical in mountain areas of Asia. In Nepal, different bee species pollinate at different altitudes. Crop pollination managed by human intervention with a variety of bee species plays an important role in overall agricultural development in different zones.
The benefits of pollination are also high in intensive agriculture, particularly plantations. The economic value of pollination services in the fruit belt of California is estimated in billions of dollars per year. Crop and biodiversity management practices that reduce either the number or abundance of pollinators can result in reduction of crop diversity both in temperate and tropical agriculture. With a loss in pollinators, seed production declines and the vulnerability to pests and climatic change increases with the resulting loss both of genetic diversity and crop productivity.
The Indian gene centre is among the 12 mega diversity regions of the world. About 25 crop species were domesticated here. It is known to have more than 18,000 species of higher plants including, 160 major and minor crop species and 325 of their wild relatives. agrobiodiversity Management Conservation, Management and Use of Agrobiodiversity (1998) Policy Paper no. 4, April 1998, National Academy of Agricultural Sciences, New Delhi, suggests some measures for
• Simple, effective and practicable mechanisms for prospecting agrobiodiversity and monitoring should be evolved. Selected amateur groups, including school and college students, should be enlisted for this purpose.
• Genetic variability of native, under-utilised species of food crops, fruits, medicinal, aromatic and other economic plants should be documented on priority. It should be supplemented through need-based introduction of useful species. Selected, hitherto unexploited, species having future potential should be researched on and adopted.
• There is an urgent need to adopt appropriate quarantine measures in the national interest. We must revisit the present National Plant Quarantine Policy, particularly in the context of bioengineered materials/genetically modified organisms (GMO).
• Characterisation, evaluation and documentation of PGR should receive a high priority. Relevant improved tools and technologies, such as biotechnology, should be deployed in future.
• The national information network and database on germplasm should be strengthened. It has also recommended the spread of awareness and for development of human resources in the space:
• Considering the relevance of agrobiodiversity in the emerging global scenario, there is a need for creating awareness and understanding about it among the public and Indian masses. Literacy campaign for conservation and sustainable management of agrobiodiversity needs to be initiated at the grass roots level, starting right with the school and gram sabha/panchayat levels.
• Suitable curricula for students and orientation courses for the teachers/trainers needs to be developed on priority. To begin with, the ICAR, through its own set-up and state agricultural universities, should take a lead. The University Grants Commission (UGC) and various Central and State Education Boards can expand this programme further.
• There is a need for literacy on PGR policy issues such as plant variety protection, breeders’ rights, farmers’ rights, sui generis system and such others. Recommendations on policy and management issues on agrobiodiversity should be widely circulated. Literature on PGR-related happenings and who’s who is not accessible to most people. In order to create greater awareness about agrobiodiversity conservation and management issues in the global context and also to evolve consensus at the national level, the draft text for biodiversity legislation should be widely circulated along with selected literature on CBD, TRIPs, UPOV-1978, FAO Undertaking on PGR, Leipzig Conference, Global Plan of Action and such others.
• Emphasis should be laid on human resource development to build required expertise in basic PGR management aspects, namely, germplasm identification, collection, characterisation, evaluation, documentation and conservation. Simultaneously, reorientation of technology generation is warranted. HRD should be further oriented towards the needed expertise, technology and awareness for germplasm regeneration and on farm conservation.
• Conservation, Management and Use of Agrobiodiversity (1998) Policy Paper no. 4, April 1998, National Academy of Agricultural Sciences, New Delhi, http://www.naasindia.org/Policy%20 Papers/pp4.pdf
• Pimbert, M., (1999) Sustaining the Multiple Functions of Agricultural Biodiversity, FAO background paper series for the conference on the Multifunctional Character of Agriculture and Land, The Netherlands, September 1999. http:// www.fao.org/docrep/x2775e/X2775E03.htm
• Sahai.S., (2010) Challenges to Genetic Diversity and Implications for Food Security in South Asia, South Asian Survey, A Journal of the Indian Council for South Asian Co-operation, Sage Publication, Volume 17, Number 1, Page 111