Screening Rice Genotypes for Drought Stress at Early Growth Stage.

Drought stress is one of the major abiotic stresses affecting growth and development of plants at all stages. Different indica rice lines respond differently to drought. The wide inherent morpho-genetic variability could be used to identify drought tolerant lines for breeding. An experiment was conducted to evaluate 75 rice experimental breeding lines for tolerance to drought stress under pot-culture in mini-greenhouse condition. The rice seedlings were subjected to two different soil moisture regimes, 100 and 50% field capacity, from 10 to 30 days after sowing (DAS). Several morpho-physiological parameters including root traits were measured at the end of the experiment, 30 DAS. Significant moisture stress X cultivar interactions were found for most of the parameters measured. Both root and shoot parameters were found important in studying and identifying drought tolerant lines during the seedling establishment stages in rice, but shoot parameters were more affected as compared to root parameters. A cumulative drought response index (CDRI) was developed by summing the individual response indices of all cultivars. The CDRI varied between 13.5 and 27.5 among the cultivars tested. Based on CDRI and standard deviation values, five and 15 lines were identified as most sensitive and sensitive to drought, respectively, 35 as moderately sensitive, and 13 and seven as most tolerant and highly tolerant, respectively. BR47 and Rex were identified as the least and most tolerant to drought among 75 lines tested. The lines identified as drought tolerant based on morphological parameters, further need to be confirmed by molecular analysis and can be used as a valuable resource in rice breeding programs to develop new genotypes best suited for drought conditions. Moreover, further studies are also needed to test these lines at different growth stages under various growth conditions to identify the stability under drought stress conditions.