Construction of a framework linkage map and genetic dissection of drought- and yield-related QTLs in horsegram (Macrotyloma uniflorum)

Horsegram (Macrotyloma uniflorum) is a legume species that is widely distributed throughout the Indian subcontinent. It is considered to be an important dietary protein supplement and nutraceutical. Horsegram has a great potential for fulfilling future pulse crop demand due to its inherent ability to grow under very low moisture conditions. However, the genome structure and organization of this crop is poorly understood, thereby limiting the effective use of gene resources for genetic improvement. We report here our construction of the first framework linkage map of horsegram, consisting of 211 molecular markers (157 SSR, 39 RAPD, 8 ISSR and 7 COS), using a mapping population of 190 recombinant inbred lines derived from a cross between parental lines HPK4 and HPKM249. The map comprises 13 linkage groups (LGs) that span 1423.4 cM, with a mean marker interval of 9.6 cM. Phenotypic data for eight agronomic traits were recorded for 2 years and utilized to detect associated quantitative trait loci (QTLs). Five QTLs for four traits related to drought (days to temporary wilting, root length) and yield (numbers of seeds per plant, days to maturity) were detected on five LGs, with an LOD threshold of 4.0. The linkage and QTL analysis reported here provides useful information for future research work pertaining to the construction of highly enriched genetic maps as well as to the development of drought-resistant and high-yielding varieties of horsegram using marker-assisted selection.