ABSTRACT

In cytoplasmic male sterility (CMS)-based hybrid cotton breeding and genetics, the construction and utilization of a high resolution linkage map can facilitate marker-assisted selection for restorer lines and allow for greater precision in the isolation of the fertility restorer genes. The objectives of this research were to develop a high resolution linkage map for fertility restorer genes of cotton using various PCR-based DNA markers. B418 (D_2-2, Rf₁) possessing male sterile cytoplasm (D_2-2) and corresponding fertility restorer gene (Rf₁), was used as female to cross with D8R3 (D₈, Rf₂) possessing male sterile cytoplasm (D₈) and corresponding fertility restorer gene (Rf₂). The resulting F₁ was testcrossed as female with Suregrow 747 containing normal fertile cytoplasm and no fertility restorer gene. The testcross population (TC₁F₁) was grown in 2002/2003 winter in the greenhouse for male fertility evaluation and DNA marker analysis. The mature bolls from the heterozygous restored fertile plants were bulk harvested and grown as TC₁F₂ (equivalent to F₂) in the field in Las Cruces, NM in 2003. Segregation analysis of male fertility in the TC₁F₁ confirmed involvement of the Rf₁ gene in controlling fertility restoration in the CMS caused by D_2-2 cytoplasm, while the Rf₂ gene did not promote male fertility restoration in this system. No distortion of segregation in fertility (786 fertile vs. 246 sterile) was noted in the TC₁F₂ population. Bulked segregant analysis was used to identify additional molecular markers (SSR, RAPD, and STS) linked with the fertility restorer genes. Two of the five previously developed STS markers successfully discriminated fertile plants from sterile plants. So far, 28 SSR primer pairs were screened using two isogenic lines, which produced 5 potential polymorphic SSR markers.