Use of Molecular Markers to Identify Potential New Sources of Root-Knot Nematode Resistance in Upland Cotton

New sources of resistance to RKN need to be identified and deployed along with established resistance genes in order to prolong the durability and effectiveness of all resistance sources.  Wild Gossypium hirsutum accessions identified as RKN-resistant in early screening programs were genotyped with SSRs linked to the known RKN resistance QTLs on chromosomes 11 and 14.  The majority of accessions were found to harbor either the chromosome 11 or 14 QTL; however, a handful of accessions did not test positive for either known resistance QTL.  Among these accessions, TX-25 and TX-28 showed levels of resistance approaching that of the highly resistant germplasm line M240 RNR.  F5 day-neutral populations of TX-25 and TX-28 were recently screened to identify RKN-resistant day-neutral plants to be carried forward in a breeding program.