1396 Cotton leaf curl disease

Cotton leaf curl disease is the major biotic constraint to cotton production in Pakistan and India.The disease causes unusual symptoms that include vein swelling, enations and the formation of leaf-like outgrowths. Cotton production during the 1990s was severely curtailed by CLCuD across the sub-continent. This stimulated interest in determining the aetiology and generating resistant varieties. The disease was shown to be caused by begomoviruses in association with a newly discovered single-stranded DNA satellite; such satellites have subsequently been shown to be widespread across the Old World and to be associated with many important diseases of crop plants. In the late 1990s, cotton varieties with natural (host plant) resistant to the disease were developed and were successful in alleviating losses. However, in 2001, symptoms of CLCuD were again evident, indicating the appearance of a resistance breaking strain of the disease. Efforts are now underway to produce transgenic pathogen-derived resistance, a strategy that is showing promise.