Developing a Screening Tool to Identify Drought Tolerance Among 100 Elite Rice Lines.

Drought stress is a major abiotic stress factor that affects growth and development of plants at all stages. Developing a screening tool to identify drought stress tolerance during seedling establishment is key to identifying stress tolerant lines for breeding. An experiment was conducted to evaluate 100 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, 25-30 DAS. Significant moisture stress X cultivar interactions were found for most of the parameters measured. A cumulative drought response index (CDRI) was developed by summing the individual response indices of all cultivars. The CDRI varied between 14.7 and 27.9 among the cultivars tested. Based on CDRI and standard deviation values, five and 28 lines were identified as most sensitive and sensitive to drought, respectively, 45 as moderately sensitive, and 16 and six as most tolerant and highly tolerant, respectively. Cheniere and RU1402174 were identified as the least and most tolerant to drought among 100 lines tested. Even though significant linear correlations were obtained between CDRI and root (R² = 0.91) and shoot (R², 0.48) parameters, root traits are important in studying and identifying drought tolerant lines during the seedling establishment stages in rice. The identified rice lines will be a valuable resource for rice breeders 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 identify the stability of these tolerant lines for drought.