GENOTYPIC RESPONSE IN RICE DURING THE REPRODUCTIVE PHASE UNDER WATER STRESS AND NON-WATER STRESS CONDITIONS

Abstract

Drought stress during the reproductive stage is a major constraint limiting rice production and productivity in rainfed upland and lowland ecologies especially in sub-Saharan Africa. This study was conducted to determine response of rice landraces and cultivated rice to water stress at reproductive growth stage, to identify sources of drought tolerance among selected rice landraces grown in coastal region of Kenya and to identity traits contributing to high grain yield under water stress conditions. Fifteen rice genotypes were evaluated in a randomized complete block design with four replications under water stress and non-water stress conditions in a steel and wire mesh screen house where weather conditions were uncontrolled. Data collection included canopy temperature, relative leaf water content, leaf rolling, and leaf drying, days to 50% flowering, spikelet fertility and grain yield per plant. The study revealed that there were no significant differences among rice genotypes for all the physiological traits measured under non-water stress conditions. However, under water stress conditions, genotypes varied significantly (P≤0.001) for all the physiological traits and in days to 50% flowering, spikelet fertility and grain yield per plant. The intensity of stress observed in this study was moderate as revealed by a relative yield reduction of 57%. Based on a selection index ranking, two local cultivars, Shingo la Mjakazi and Kitumbo were found to be moderately water stress tolerant and therefore potential sources of drought tolerance trait. All the other landraces were identified as water deficit susceptible. Under water stress conditions spikelet fertility showed a strong positive correlated with grain yield (0.62**) and was the most important contributor to higher grain yield and may be targeted to indirectly select for grain yield under water deficit conditions