Drought Stress Tolerance Screening of Elite American Breeding Rice Genotypes Using Low-Cost Pre-Fabricated Mini-Hoop Modules

Drought is a major abiotic stress factor affecting the growth and development of plants at all stages. Developing a screening tool for identifying drought stress tolerance during seedling establishment is important in the deployment of rice varieties suited to water-limited growing environments. An experiment was conducted to evaluate 100 rice genotypes, mostly belonging to the tropical japonica subspecies, for drought stress tolerance using low-cost, pre-fabricated mini-hoop structures. The rice seedlings were subjected to two different soil moisture regimes- control pots managed at 100% and drought pots at 50% field capacity, from 12 to 30 days after sowing (DAS). Several morpho-physiological parameters including root traits were measured to assess the response of genotypes to drought stress. Significant moisture stress × genotype interactions were found for most of the parameters measured. A cumulative drought stress response index (CDSRI) was developed by adding the individual response indices of all cultivars. Based on CDSRI and standard deviation values, 5 and 28 genotypes were identified as highly sensitive and sensitive to drought, respectively, and 45 as moderately sensitive. On the other hand, 16 and 6 genotypes were classified as tolerant and highly tolerant to drought, respectively. Cheniere, a released cultivar, and RU1402174, an experimental breeding line, were identified as the least and most tolerant to drought among the 100 genotypes tested. Significant linear correlation coefficients were obtained between CDSRI and root growth parameters (R2 = 0.91, n = 100) and CDSRI with shoot growth parameters (R2 = 0.48, n = 100), revealing the importance of root traits in studying and identifying drought tolerant lines during the seedling establishment stages in rice. The tolerant rice genotypes identified will be valuable for rice scientists in studying the mechanism for early season drought as well as for rice breeders for developing new genotypes best suited under growing environments prone to early-season drought.