CULTIVAR DIFFERENCES IN EPICUTICULAR WAX CONTENT AND EXPRESSION ANALYSIS OF β-keto acyl CoA synthase 1 (kcs1) AN EPICUTICULAR WAX SYNTHESIZING GENE IN GROUNDNUT (Arachis hypogaea L.) UNDER DROUGHT STRESS

Groundnut (Arachis hypogaea L.) is one of the important oil seed crops cultivated widely in the parched and arid regions and drastically affected by drought conditions worldwide. To mitigate the drought stress, plants adapt their aerial parts with epicuticular waxes to prevent non-stomatal water loss and reduce heat load. Genotypic variation exists in the accumulation of epicuticular wax content (EWC) in many crop plants including groundnut. The present study compared the differences in EWC, RWC (relative water content), CMS (cell membrane stability) and expression of kcs1 gene in six local groundnut cultivars namely Harithandra, Vemana, Anantha, Kadiri-5, Kadiri-6 and Kadiri-9 subjected to drought stress. The epicuticular wax content was increased gradually from day-10 to day-60 (growth stage) and was decreased day-70 to day-100 (harvest stage) in all cultivars under control conditions. Results revealed that the cultivar Kadiri-9 showed higher EWC than other cultivars under control conditions throughout the experiment. One-month-old groundnut plants grown under normal conditions were subjected to drought stress for 10 days. Drought stress resulted a significant increase in the EWC in all groundnut cultivars, however the EWC was increased by two fold in the cultivar Kadiri-9, but less than one fold increase in the EWC in other cultivars. Ten-days after drought stress treatment, cultivar Kadiri-9 exhibited significantly higher RWC and lesser electrolyte leakage than the other cultivars. SEM leaf images clearly showed more densely accumulated wax crystals on the leaves of cultivar Kadiri-9 and were less densely accumulated on leaf-surface of other cultivars. Real Time - PCR analysis further revealed that relative expression of kcs1 gene was significantly increased in cultivar Kadiri-9 compared to other cultivars under drought stress. This suggests that the cultivars with higher EWC may mitigate the water stress effects by conservation of water more effectively than the cultivars with lower EWC.