Stress indices and selectable traits in SALTOL QTL introgressed rice genotypes for reproductive stage tolerance to sodicity and salinity stresses

The present study was carried out by evaluation of twenty two rice genotypes including 18 SALTOL QTL introgressed rice genotypes under salt stress conditions during 2009 and 2010. It aimed to know the tolerance and productivity potential of marker assisted breeding (MAB) derived material under precisely controlled normal, sodicity (pH ∼9.5) and salinity (EC 10dS/m) micro-plots environments, judge the relative effectiveness of the stress tolerance indices and to understand the implications of eight plant traits in influencing yield potential and stress tolerance. Mean squares due to genotypes were highly significant for all nine characters studied. Across genotypes, the seedling stage tolerance was associated with grain yield performance and adult stage salinity tolerance. The SALTOL lines IR 84645-305-6-1-B, IR84649-275-3-2-B and IR84649-292-3-1-B performed significantly better in terms of seedling stage tolerance, grain yield and STI (stress tolerance index) as compared to sensitive check under sodic as well as salinity stress environments. STI was found to be a better selection criterion than stress susceptibility index (SSI). Yield potential was directly correlated with yield under stress and STI under both stresses. Interestingly, STI values for sodicity stress were positively correlated with those of salinity stress, thus sodicity stress tolerance could be predictive of salinity stress tolerance or vice versa. The STI values under moderate sodic and high saline conditions were positively correlated with plant height, total and productive tillers, biomass, grain yield and harvest index in normal and both stress environments thus revealing importance of these traits for indirect selection in the MAB derived material.