Development of mapping populations and their characterization for drought tolerance in wheat

Six sets of Recombinant Inbred Lines (RILs) viz., HW2004/HD2877, C306/MACS2496, NI5439/HD2012, C306/NI5439, C306/HD2851 and HD2888/HD2851 were produced by crossing drought tolerant and susceptible genotypes. A majority of traits differed between drought tolerant and the drought susceptible genotypes. The contrasting difference in mean indicated the suitability of parents for developing recombinant inbred lines. Positive correlation of plant height (r=0.531), tiller number (r=0.722), relative water content (r=0.729), thousand kernel weight (r=0.838), harvest index (r=0.733), biological yield (0.816) with yield were recorded in the genotypes. Similarly in RILs, plant height, tiller number, number of grains, biological yield and thousand kernel weight showed significant positive correlations with yield at Delhi and Indore. A total of 832 SSR markers were utilized to survey the parental polymorphism between drought tolerant (HW2004) and drought susceptible (HD2877) genotypes. Out of these 132 were polymorphic and only 91 markers covering all the 21 chromosomes were selected to characterize the parents involved in development of mapping populations. Amongst, 75.82 per cent were polymorphic between C306 and MACS2496, 58.43 between HD2888 and HD2851, 62.50 between C306 and HD2851, 56.91 percent between NI5439 and HD2012. Only 48.89 percent of SSR markers were polymorphic between drought tolerant genotypes, C306 and NI5439 which may be due to presence of similar genomic regions between the two. A higher per cent of polymorphic markers were located on B genome. Based on molecular analysis the eight genotypes involved in mapping populations were grouped into two clusters. Drought tolerant genotypes fell in one group while susceptible in second group. The mapping populations developed for drought tolerance are important resources for genetic dissection of drought tolerance in wheat.