Association analysis in F1 and F2 generations of rice under reproductive stage drought stress

Drought stress occurring at reproductive stages has severe impact in rice yield as it adversely affects grain filling. Rice genotypes with earliness (to avoid terminal drought), better internal water balance and deeper root system (to extract water from deeper layers of soil) tend to withstand to a greater extent and give nominal yields under drought situations. In order to understand the nature and extent of association between traits of drought tolerance and grain yield under reproductive stage drought stress, association analysis was performed in F1 and F2 generations of rice. In F1, days to 70% RWC and root traits viz., root thickness, root/shoot ratio, root length, root volume and dry root weight exhibited significant positive association with grain yield/plant while in F2, spikelet fertility and root traits viz., root length, dry root weight, root thickness and root/shoot ratio had positive and significant association with grain yield. Negative and significant association was noticed between grain yield and days to 50% flowering, leaf drying and drought recovery scores in F1 and between grain yield and days to flowering in F2. Positive intercorrelation was noticed between spikelet fertility and root traits in both F1 and F2. Hence selection based on earliness and root characters will be helpful in identifying genotypes with better drought tolerance capacity and grain yield under rainfed conditions. Productive tillers/plant, 100 grain weight and harvest index in F1 and harvest index, root length and dry root weight in F2 were the major contributors of grain yield by way of their positive and high direct effects.