Spot blotch resistant (IBON 18) and susceptible (RD 2508) lines were crossed to investigate inheritance of resistance and to identify simple sequence repeats (SSRs) associated with resistance. F1 resistance was intermediate and suggested additive nature of inheritance. Three additive genes was noted in the distribution of F3, F4 and F5 generations. In F6 and F6-7, the quantitative and qualitative approaches also suggested the control of three resistance genes. The parents and the RILs (F6/F6-7) were grown in four environments and spot blotch severity recorded. Forty five SSR primers, specific for chromosomes 1 (7H) and 5 (1H), were applied. Of these, 12 were polymorphic between the parents, and between the resistant and susceptible bulks. Three markers BMS 32, BMS 90 and HVCMA showed association with resistance, which was further confirmed through selective genotyping. The co-segregation data on the molecular markers (BMS 32, BMS 90 and HVCMA) and spot blotch severity on 173 RILs was analyzed by single marker linear regression approach. Significant regression suggested linkage among BMS 32, BMS 90 and HVCMA and the three resistant genes (designated as Rcs-qtl-5H-1, Rcs-qtl-5H-2 and Rcs-qtl-1H-1.) respectively. These markers explained 28%, 19% and 12% of variation respectively, for spot blotch resistance among the RILs.
microsatellite markers; molecular marker; spot blotch; Cochliobolus sativus; barley
