Source: International Plant Genetic Resources Institute (IPGRI)

Swollen shoot disease. Palm leafhopper. Banana bacterial wilt. Asian soybean rust. Clover-root weevil. A quick glance at a day’s headlines reminds one that around the world, farmers face an onslaught of pests and diseases. For those who can afford it, the answer may take the form of chemical protection. Many farmers, however, including those most dependent on their own crops for their survival, cannot afford chemicals. Worse, some pests and diseases remain invulnerable and others quickly develop resistance.

The only long-term, sustainable solutions are to be found in the existing diversity of agricultural plants. One of the main purposes of the new International Treaty on Plant Genetic Resources for Food and Agriculture (ITPGRFA), whose Governing Body meets for the first time in Spain on June 12, is to make it easier for farmers and scientists to improve agriculture by making it easier for them to access agricultural biodiversity.

This diversity, nurtured over generations by farmers and scientists, takes many forms. Growing many different species, for example, reduces the risk of a calamitous epidemic wiping out the entire harvest and is a common form of management for poor farmers. More important, however, is the diversity within a single species.

Having grown in different environments and been subjected to different pests and diseases, different varieties of crops have accumulated different genetic characteristics. These traits may give a plant resistance to disease, and farmers and scientists can use these plant genetic resources to transfer new, desirable traits to their favoured varieties.

That is how the rust diseases of wheat were brought under control. Breeders screened samples of wheat collected from farmers around the world. They found varieties, often low-yielding ones, that were resistant to particular kinds of rust disease, and used those to breed new high-yielding and resistant varieties. Unfortunately, the rusts evolved to overcome the resistance. Breeders continued the search and found individual varieties that demonstrated so-called durable resistance, lasting several generations over large areas, to various kinds of rust. By the 1990s, almost all the new wheat varieties being made available by public-sector breeding programmes around the world incorporated durable resistance from these few original donors.

The importance of plant genetic resources in the pursuit of improved agriculture is impossible to underestimate. In purely financial terms, breeding for resistance to leaf rust alone has been worth more than US$ 5.3 billion to developing country farmers growing spring wheats, for a return of more than US$27 for every dollar invested (at 1990 values). Dollar values and returns on investment, however, do not capture the significance to poor farmers of more secure food supplies and the potential they bring for better health and higher incomes.

The story of leaf rust in wheat could be told for countless other pests and diseases of countless other crops. Indeed, a new chapter is being written for wheat itself, with the emergence late last year of a new and extremely virulent strain of wheat stem rust, Ug99. Of the 44 million hectares planted worldwide to known varieties of wheat, only about 130,000 hectares – less than 0.3% -- has any resistance. The cost just to Africa, which is where Ug99 first appeared, could be as high as US$ 1 billion. There is every likelihood that the epidemic will spread to other parts of the world, knocking out perhaps 10% of global wheat production, worth US$ 9 billion a year at current prices.

The search for a long-lasting solution to the new strain of stem rust will focus on the plant genetic resources of existing wheat varieties. Agreements to be signed with the International Treaty’s Governing Body will give wheat breeders everywhere much better access to more than 165,000 varieties of wheat. Not just wheat, but some 64 crops and forages that cover 80% of people’s food needs. Without the access guaranteed by the Treaty, efforts to fight wheat stem rust – and all the other diseases out there – will be severely hampered.