Nematodes are the number one yield-robbing disease in cotton. Because Temik is the most widely used nematicide in cotton today, growers have been concerned by the recent announcement of a scheduled phase-out of all registered uses of Temik by 2018.
“Host-plant resistance would be an economic and environmentally favorable alternative to nematicide use, but only a few varieties are resistant against root-knot nematodes, none are fully resistant; and no cotton varieties are resistant to reniform nematodes,” explains Dr. Robert L. Nichols, Senior Director, Agricultural Research, Cotton Incorporated.
In 2002, Cotton Incorporated began a concerted research effort to identify sources of nematode resistance in Gossypium species, locate the genes, determine their inheritance, release germplasm carrying the resistance genes, and publishing genetic markers that would enable breeders to efficiently transfer the genes to advanced lines. Cotton Incorporated has not only supported public breeders, but actively communicated with private seed-breeding companies welcoming their participation.
Significant progress has been made. Root-knot nematode (RKN) resistant lines produced by USDA-ARS in the 1970s have been crossed with more recent cultivars to facilitate forward crossing to elite lines. Additional research has more fully characterized a two-gene system with potential to improve the level of RKN resistance available for transfer to commercial varieties.
“Our current work is targeted toward understanding a region of cotton chromosome 11 that has a concentration of resistance genes to nematodes and the fungus that causes Fusarium wilt. We hope that description of this region will fully characterize anchor genes for development of multi-genic disease resistance to both nematodes and diseases,” adds Nichols. Cotton Incorporated and cooperators have also identified and characterized genes for reniform nematode resistance. A release of reniform nematode-resistant germplasm has been made and another is anticipated.
“We encourage private seed-breeding companies to accept the challenge to develop cultivars with high levels of resistance to RKN; the tools for such an initiative are available now,” says Nichols. Cotton Incorporated and cooperators will continue to work on development of reniform nematode resistance. When this effort began, there were no available sources of resistance to reniform nematode in cotton. Now one source has been released; another is near release; and others are in development.