Drought Stress and Variability Assessment Among indica Rice Lines 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 a 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, 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 traits for each line. The CDRI varied between 8.7 and 21.5 among the 75 rice lines tested. Based on CDRI and standard deviation values, 6 and 27 rice lines were identified as the most sensitive and sensitive to drought, respectively. 41 rice lines were identified as moderately drought tolerant, and only one line “IR86126-104-B-B” was found as highly tolerant to drought. The lines identified as drought tolerant based on morpho-physiological analysis can be used as a valuable resource in rice breeding programs to develop new genotypes best suited for drought conditions. However, further studies are needed to test these lines at different growth stages under various growth conditions to assess the performance stability of these tolerant lines under drought stress conditions.