Crop diversity has its impacts in farmers’ fields – in situ – and in the markets and supermarkets where consumers increasingly demand choice. A sweeping study of farm data in the U.S. confirms a narrowing of the number of crops grown in most parts of the country in the past three decades as farmers specialize and intensify agricultural production.
Similar processes are at work in other parts of the world, and are often characterized by a decrease not just in the number of crops grown, but also in the diversity within the range of varieties in the field. While change is inevitable in farming systems, as farmers experiment with and adopt new crops and varieties, this narrowing of crop diversity at both the species and genetic level has consequences for the productivity, stability and resilience of the global agri-food system.
Recognizing this, plant genetic scientists have been assembling and managing ex situ collections of crop diversity in a systematic manner for over a century. They have collected hundreds of thousands of samples of traditional crop varieties and related wild species from a myriad of remote, dispersed locations and have safeguarded them in genebanks. Genebank collections provide a means to make unique diversity available cheaply and effectively, for the long-term, so that it may be used by breeders in the future, returned to farmers and offered to consumers.
Without access to the diversity already stored in genebanks, researchers trying to understand the diversity of a crop and the plant breeder embarking on an improvement program would have little alternative but to create their own collections from scratch. This would involve locating the diversity in farmers’ fields or in the wild (assuming it is still there); negotiating with multiple countries, institutes and farmers for access; carrying out arduous fieldwork over several years; cleaning and health testing collected samples; and, if the process is not to be repeated, carefully documenting and conserving the resulting material so that it may be used again. For a single breeder, this process would be expensive and time-consuming, but perhaps manageable; for hundreds of independent breeders and researchers around the world, the cumulative cost would be prohibitive and the effort inefficient.
A study carried out by the National Bureau of Plant Genetic Resources in India determined that 250 rice samples can be collected during an exploration trip of about 15 to 20 days. Theoretically, it would take at least 200 successful trips and over 10 years to gather 50,000 samples, and several more years to clean and multiply them for use. We know from a 2010 costing study that to fully incorporate 50,000 samples of cultivated rice (wild rice would be considerably more expensive) into a genebank collection would cost USD 6 million, or USD 120 per accession, not including the costs of building the facility or of ongoing conservation thereafter. But, major collections of rice already exist, underpinning global rice production. The International Rice Research Institute (IRRI) conserves more than 100,000 different samples of rice in a cost-efficient manner, obviating the need and expense of having each rice breeder create their own collection of genetic resources.
Today, nearly every country maintains a national genebank. The value placed by governments on crop diversity is reflected in the dramatic increase in the past 30 years in the number of collections and of the accessions they hold. FAO documents that 7.4 million accessions (about 2 million of which are estimated to be unique) are now conserved ex situ in over 1,750 facilities worldwide. The work of such genebanks is vital to national efforts to conserve and use crop diversity, and makes invaluable contributions to regional and global germplasm exchange.
However, there are distinct advantages to the crop improvement and research community in also establishing large, mega-diverse, international ex situ collections. Housed in advanced facilities, under the care of specialist staff who are able to refine management protocols for particular crops and expeditiously distribute material worldwide to all types of users in a safe manner, such collections are a unique component of the global system for the conservation of crop diversity. The genebanks of the CGIAR centers, (including other international, regional, and national collections) have helped create a rational system, recognized by the International Treaty, in conserving and making available a significant proportion of the world’s unique accessions of crop diversity.
The advantages of such centralization are especially obvious when considering the international distribution of crop diversity. For example, while wheat seed is one of the easiest to store, ensuring that the seed is free of karnal bunt (a dangerous fungal disease) demands professional disease indexing and strict adherence to health control measures at every step of the conservation process. Spreading potentially devastating diseases is a major risk associated with the exchange of crop diversity, especially in countries where phytosanitary controls may be inadequate.