Toward Sequencing Cotton Chromosome 11 Regions Responsible for Root-Knot Nematode Resistance

While progress in cotton genomics may be lagging behind that in other agronomic crops, the past decade has seen substantial growth and development, conceptually and technically. At a Cotton Incorporated coordinated meeting held in Dallas, TX in October, 2007 to discuss genetics of root-knot nematode (RKN) Meloidogyne incognita resistance in cotton, several research groups established the importance of chromosome 11. The concentration of RKN resistance factors on chromosome 11 indicates that much can be gained by fine mapping this genomic region. The laboratories of Drs. Roberts (UC Riverside, CA), Ulloa (USDA-ARS, WICSRU, CA), and Chee (UGA, GA) will develop a collaborative strategy to fine map the region of the RKN gene on chromosome 11, where several nematode and other disease resistance genes are located. They will also coordinate efforts with Dr. Jenkins’ laboratory and other RKN researchers. In several described sources of genetic resistance to RKN, including ‘Acala NemX’ and Auburn 623 interaction of at least two genes and transgressive segregation occur, and resistance to RKN in cotton may involve the interaction of several genes. With the support of Cotton Inc., Cary, NC, two BAC libraries are being developed from these two different germplasm resistance sources, N901 (NemX origin) and M120 (Auburn 623 origin). The new genome BAC resource will allow us to fine map RKN resistance region(s) on chromosome 11 and to obtain DNA sequence information for marker development and gene discovery. Our ultimate objective is to accelerate the incorporation of RKN resistance in commercial cultivars by increasing knowledge about the inheritance of RKN resistance genes, developing improved germplasm with the RKN resistance genes, and developing selection markers for the resistance.