Mapping of Quantitative Trait Locus (QTLs) that contribute to Drought Tolerance in a Recombinant Inbred Line Population of horsegram (Macrotyloma uniflorum)

Horsegram (Macrotyloma uniflorum) is a drought hardy legume which can be grown in varied soil and temperature regime. It is an important food legume with environmental, nutritive and medicinal benefits. But in terms of genetic improvement it still lags behind other legumes. To get insight into the genetics of tolerance to drought stress, quantitative trait loci for drought tolerance traits were identified using an intraspecific mapping population comprising of 162 F8 Recombinant Inbred Lines derived from a cross between HPKM249 and HPK4. A total of 2011 markers were screened on parental lines for polymorphism survey, out of which 493 markers were found to be polymorphic and used for genotyping of the RIL population. Of these 493 polymorphic markers, 295 were assigned to ten linkage groups at LOD 3.5 spanning 1541.7cM with a mean distance of 5.20 cM between adjacent markers. This linkage map along with the phenotypic data for drought tolerance traits was used to identify regions of the horsegram genome in which the genes for the qualitative traits linked to drought tolerance located. A total of seven QTLs were identified for six different drought related traits. One QTL for malondialdehyde content on linkage group 2, two QTLs for root length on linkage group 3 & 9, one QTL each for proline content and chlorophyll content under drought stress on linkage group 4, one QTL each for root dry weight and root fresh weight on linkage group 5 were identified using composite interval mapping. The linkage map and identified QTLs will be utilized in Marker Assisted Breeding and increase our understanding on the physiology of drought stress tolerance. It will also aid in molecular breeding efforts for further genetic improvement of horsegram.