Genetic variability assessment of rice genotypes for drought stress tolerance under controlled conditions

Drought is the major abiotic stress that limits rice productivity in rainfed lowland and upland ecosystems. Rice yields in drought-prone rainfed systems remain low and tend to be unstable. We investigated the response of fifteen rice genotypes under control and drought conditions. Irrigation was given regularly for both the control and drought treatments up to flowering according to their duration and then irrigation was withdrawn for a period of 14 days to create drought conditions. Observations on physiological parameters were taken at this stage. Results revealed that total biomass plant-1, total grain weight plant-1, number of panicles, relative water content, membrane stability index, chlorophyll a, total chlorophyll content and plant height decreased significantly under drought conditions compared to the control condition. Analysis of genotype and genotype × trait exhibited that PC1 and PC2 governed 56.20 % variability under control conditions, while under drought conditions, they accounted for 54.6 % of variability. In drought conditions, the most contributing traits were found to be chlorophyll a content (35.3 %), total grain weight (33.5 %), total chlorophyll content (30 %), plant height (26.6 %), total biomass (24.7 %) and number of panicles (20 %). Since total grain weight governed maximum genetic variability, clustering of genotypes based on relative grain weight resulted in four distinct clusters. Out of 15 rice genotypes, 6 belonged to the efficient cluster, 5 to the moderately efficient cluster, 3 to the moderately inefficient cluster and one was included in the inefficient cluster. The genotypes identified in this study may be utilised as ‘donors’ by the breeders to develop drought-tolerant cultivars in rice.