Safeguarding the Future of US Agriculture - Global Crop Diversity Trust

can only be done with access to gene resources, a vigorous search for newresistance, and transfer of that resistance to an adapted variety.More volatile weather and climate change. Farmers are concerned aboutthe prospect of an increasingly variable or volatile climate, with possiblechanges in the frequency and intensity of droughts, flooding, and storms,leading to new levels of erosion and water-logging in some areas, drought ordesertification in others. While these changes alone put additional stress oncrops, they also open up the possibility that agricultural pests may expandtheir range, or proliferate in the favorable conditions brought about bychanges in climate.Increased risk of introduced pests. The volume of global travel and of foodimports increases each year, heightening the risk of accidental introductionsof plant pests. Already today, there are more than 2,000 species of nonindigenousinsects and mites in the conterminous U.S., and non-nativeinsects are responsible for an estimated $14 billion in annual crop losses. 2 Inaddition to accidental introductions, there is the threat of intentionalintroductions. Based on this concern, the US government in 2004 issued apresidential directive that establishes a National Plant Disease RecoverySystem charged with “responding to a high-consequence plant disease withpest control measures and the use of resistant seed varieties within a singlegrowing season to sustain a reasonable level of production for economicallyimportant crops.”Many crops are especially vulnerable to diseases due to their narrow geneticbase—in part a product of their history as introductions from distant areas of cropdiversity; in part a result of plant breeding methods and farming practices. Only ahandful of crops grown in the US—sunflower and strawberry among them—weredomesticated from wild plants native to the United States. The vast majorityevolved in far-flung “centers of origin,” where farmers selected them for traits tosuit their needs and carried them along as they moved from place to place.In addition, farmers today tend to rely on a handful of high-yielding varieties at anygiven time, further narrowing a crop’s genepool. Therefore, the genetic diversity ofmost major US crops represents only a tiny fraction of the total genetic diversityavailable in that species.This is true for soybean and corn, the two largest crops produced in the US. AllUS soybean varieties can be traced back to a dozen strains from a small area innortheastern China. 3 And while the US produces about half of the world’s corn,this vast production is based on using less than 5 percent of the maize diversityavailable worldwide.In the past, plant breeders have successfully drawn on genetic variation found incrops grown in all corners of the globe to bolster US and world agriculture, oftenstaving off disaster. Tomato, for example, has benefited from its wild relatives,native to the Andean region of South America. There are at least 44 diseases oftomato to which wild species are resistant. About half of these resistance traits havealready been transferred to cultivated tomato. Resistance to a particular disease is8 FIGHTING OLD AND NEW DISEASES IN CROPS