Four lentil varieties of small seeded group (PL-639 and PL-406) and bold seeded group (K-75 and L-4076) mutagenised through gamma rays (10, 20 and 30 κR), EMS (0.04 M), sodium azide (0.05 M) and their combinations were evaluated for induced genetic variability and to identify the drought tolerant mutant lines and the trait(s) responsible for enhancing grain yield under rainfed condition. The findings suggest that materials ought to be tested in both moisture stress and moisture non-stress conditions so that the favourable alleles under drought can be maintained as well as the selection response under favorable condition can be maximized. Yield under drought (Yd), yield potential (Yp), drought susceptibility index (S) and geometric mean (GM) were considered as the potential indicators for assessing drought resistance of a mutant line. Correlation coefficients between these parameters revealed that GM was positively and significantly correlated with both Yd and Yp. There was significant but negative correlation between S and Yd, while no significant correlation between S and Yp was observed. It was very clear from the correlation studies that for the enhancement of yield potential under both the conditions selection should be based on GM rather than on S, because S is a better measure of drought tolerance than a measure of performance under stress. Further, selected mutant lines were evaluated for different physiological parameters (nitrate reductase activity, wax content and protein content) in M4 generation and most of them showed higher values for NR activity and wax content. NR activity and wax content may be used as the more reliable parameters to form the basis of selection under rainfed conditions.
Induced mutations, drought tolerance, drought susceptibility index, NR activity and lentil
