Testing and validating alleles (or QTLs) conferring resistance to reniform nematode, Rotylenchulus reniformis, from M713 Ren4 in a different genetic background.

Auburn University’s cotton breeding program was initiated on the industry need for reniform nematode, Rotylenchulus reniformis, resistance. The program participated in a series of joint efforts to identify and breed for potential resistant germplasm. In 2013, M713 Ren 1-5 were screened and a diallel was initiated to combine potential resistance with good yield. One particular cross, M713 Ren4 x UA 103, was advanced in a single boll descent by hand-selfing each generation to the F5. In 2017, a field trial was performed in Belle Mina, Al, to evaluate six promising F5 lines, the parents and two commercial checks under reniform nematode pressure. All lines had significantly higher yield than the commercial checks, while four lines were higher than the M713 parent. It is postulated that M713 Ren4 contains introgression segments of QTLs on chromosome 21 (Renbarb1 and Renbarb2) from GB713 that provides resistance to reniform. In recent studies, Renbarb1 and Renbarb2 are resolve in one locus (Renbarb2) and marker BNL3729 strongly associated with the resistant phenotype. To validate this, progenies from these six lines will be genotyped by using five markers spanning around QTL (Renbarb2) along with BNL3729.