ABSTRACT

Presently, no known single germplasm has resistance to both Meloidogyne incognita and Rotylenchulus reniformis, the two nematodes causing the greatest economic loss on cotton. Gossypium barbadense (Tx110) is resistant to R. reniformis and Gossypium hirsutum (M315-RNR) is resistant M. incognita. Resistance to each nematode species in the F₁ generation of an M315-RNR x Tx110 cross were identical to the resistance of the parents and were inherited as dominant traits. Segregation of resistance to R. reniformis in the F₂ individuals indicates resistance was inherited as a quantative trait that is controlled by multiple genes. Segregation of resistance to M. incognita in the F₂ individuals indicates resistance was inherited as two genes. Development of a marker-assisted selection (MAS) system for resistance to both M. incognita and R. reniformis would increase the efficiency of breeding. A RFLP map has been developed based upon progeny from a cross between G. hirsutum and G. barbadense. One hundred and ninety-two of the available 566 RFLP loci of this genetic map were screened using bulk segregant analysis (BSA). Twenty-one RFLP loci were found to be tentatively linked to resistance to either M. incognita or R. reniformis and were screened subsequently against the segregating F₂ individuals. To date, 2 RFLP loci have been found <30 cM and therefore linked to resistance for M. incognita. Additional RFLP loci will be screened for linkage to loci for resistance to each nematode species.