Morpho-Physiological Characterization of Rice Cultivars for Early-Season Soil Moisture Stress Response.

Drought stress is like a syndrome that affects several crop growth and physiological processes. The majority of rice produced in the southern USA is drill-seeded, where permanent flooding is established after the fourth leaf stage, which may subject rice seedlings to early-season moisture deficits. A greenhouse experiment was undertaken to evaluate the performance of 15 rice cultivars commonly grown in Mississippi to early-season soil moisture stress. The rice seedlings were subjected to three different soil moisture regimes, namely, 100, 66, and 33% field capacity, from 10 to 30 days after sowing (DAS). Soil moisture stress X cultivar interactions were found significant (P˂ 0.001) for most of the measured morpho-physiological parameters, including root traits. A total drought response index (TDRI), developed based on means and standard deviations by summing the individual drought response index of all cultivars, varied from 22.9 to 30.7 for the cultivars tested. Based on TDRI, CL XL729 and CL142-AR were identified as the least and most drought-tolerant cultivars, respectively. The positive and linear coefficient of determination between shoot and root TDRI (R² = 0.64) indicate that any or both of the traits could be used to determine the variability for drought tolerance in rice genotypes. In short term, the identified tolerance and the numerical scores among the rice cultivars will be helpful for the rice producers to select a variety best suited for a niche environment. In long term, rice breeders may select the drought tolerant genotypes to develop new cultivars adapted to water-limited rice growing conditions.