Linkage mapping and identification of quantitative trait loci associated with bacterial leaf blight resistance and gum content in cluster bean using the interspecific population (HG563 x Cyamopsis serrata)

Cluster bean [Cyamopsis tetragonoloba (L.) Taub] is an important leguminous crop of India, accounting for nearly 80% of the global production. The seeds of this economically important crop are used in various industrial applications worldwide like, textile, cosmetics, pharmaceuticals, mining, petroleum, natural gas, oil industries etc. Despite such high economic value, the productivity of this crop is quite low. One such major constraint in the production of cluster bean is bacterial leaf blight disease caused by Xanthomonas campestris pv. Cyamopsidis. Yield losses of up to 58-68% have been reported in case of severe infestation. Therefore, there is a need to formulate suitable breeding strategies to overcome the yield losses. But the lack of complete understanding of underlying genomic base in cluster bean is a major constraint in developing high-yielding and resistant cultivars/varieties. Here we report the first linkage map construction at the level of interspecific polymorphism using F3-4 segregating population based on Cyamopsis's the basis of microsatellite markers of cluster bean and other legume crops which can further advance the breeding programs. An interspecific cross was developed in our laboratory using a bacterial blight resistant wild species (C. serrata Schinz.) and a moderately susceptible with high gum content cultivar (HG563). A total of 177 SSRs comprising EST-SSRs from cluster bean and ESTs as well genomic SSRs from other legumes were used in molecular analysis and 38 SSRs were found polymorphic. Linkage analysis revealed that nine markers (CBN21, CBN16, CBN17, CTF234, CBN03, CBN11, CTN15, CTN14, and GDR22) formed a single linkage group spanning 190 cM of cluster bean genome. Four minor QTLs were identified in interspecific cross for plant height (qPH(1.1)), hundred seed weight (qHSW(1.1)), disease resistance (qPDI(1.1)), and gum content (qGC(1.1)) mapped on single linkage group at 39.41, 123.41, 112.41 and 102.41 cM, respectively. The LOD values for all four QTLs ranged from 3.3 to 15.5. (above the threshold LOD > 3.0). Marker interval of CTN15 and CTN14 spanning 35.4-190.0 cM distance harboured all the four QTLs. Interestingly, plant height QTL was found only 4.8 cM apart from CTN 15 SSR marker, which can be exploited further for cluster bean improvement programs in future.