1324 Recent Advances in Nematode Management in U.S. Cotton

The two most economically important plant-parasitic nematodes infesting cotton (Gossypium hirsutum) in the United States are the root-knot (Meloidogyne incognita) and the reniform (Rotylenchulus reniformis) nematode. The common means of managing these pests is use of in-furrow or seed-treatment nematicides, or by rotation with non-host crops or resistant cultivars of crops grown in rotation. Until 2007, low grain prices limited use of corn (Zea mays) or soybean (Glycine max.) in cotton rotations. Nematicides are not fully effective in preventing damage to cotton, in part because they do not persist in the soil or the cotton seedling at effective concentrations for more than about 30 days after application. Recent research suggests that nematicides may be more advantageously targeted by considering the yield potential of the cotton on the specific soil as well as the population of the pest nematode species. While root-knot resistant cotton cultivars have been available for some time, they are only partially effective and/or selectively adapted across the diverse growing conditions of the U.S. Cotton Belt. Reniform resistant cotton cultivars have been wholly unavailable. Recent work by USDA-ARS and public universities has resulted in superior agronomic germplasm releases with high levels of root-knot resistance and the first release of reniform resistant germplasm. The reniform resistant releases were derived from Gossypium longicalyx by means of a triple-species hybrid. In both cases, the releases are, or shortly will be, accompanied by publication of genetic markers closely linked to the resistance genes.