Molecular mapping and tagging of powdery mildew tolerance gene(s) in sesame (Sesamum indicum)

Abstract

Sesame (Sesamum indicum L.) is an important oilseed crop of India. Powdery mildew causes significant yield loss. Identifying sources of tolerance / resistance, studying inheritance of  powdery mildew and mapping of disease tolerance gene(s) are essential for development of high yielding varieties with tolerance to disease. Thirty accessions were screened for tolerance to powdery mildew, 18 were found susceptible while, 12 tolerant. Among the genotypes, Swethatil was found to be highly susceptible (87.65 % PDI (Percentage Disease Index)) while PKDS 37 was highly tolerant (30.86 % PDI). The mapping population for tagging the gene(s) conferring tolerance to the disease was developed of the cross between a tolerant variety PKDS 37 and the susceptible parent Swethatil. Study of segregating population revealed that tolerance to powdery mildew was governed by two independent recessive genes in complementary epistasis mode. Sixty eight RAPD markers were found polymorphic between the parents and of them, four markers, viz. OPA 7, OPAE 6, OPAE 11 and OPM 12 were clearly distinguished the susceptible from the tolerant bulks by bulked segregant analysis. Assigned to one linkage group two markers OPAE 6 and OPM 12 have been found to be tightly linked to powdery mildew tolerance gene Pm 1 at a distance of 3.6 cM and 4.8 cM respectively on either side. The markers flanking the trait can be used in marker assisted selection/breeding for resistance to the disease and this region is a potential target to the fine mapping.