Evaluation of Morphological Behavior of Some Rice Genotypes under Drought Stress

Drought stress is a major constraint for the production and stability of crop yields. Analysis of reproductive traits and their response to drought can be useful to identify drought tolerant rice genotypes. The aim of this study was to evaluate the morphological behavior of some rice genotypes under different environmental conditions in the reproductive stage.

This study was conducted in greenhouse of Sari Agricultural Sciences and Natural Resources University, a factorial experiment based on a completely randomized design in 2018. The experimental factors included rice genotypes (IR64, drought sensitive and Dinorado and Moroberecan, drought tolerant) and drought stress levels (normal irrigation and re-watering).

Analysis of variance of data showed that the effect of genotype, drought stress and genotype × drought stress interaction on studied traits was significantly different, indicating that rice genotypes behave differently under different environmental conditions. Comparison of simple correlation coefficients between different traits of rice genotypes under normal irrigation showed that yield had a positive and significant correlation with tiller number (r = 0.97). However, under drought stress, yield with tiller number (r = -0.66) was negatively correlated with flag leaf length, length and weight of panicle, number of primary and secondary spikelet, number of filled grains in panicle and percentage of panicle fertility percentage were positive and significant had. The results of stepwise regression to justify the variation of yield of rice genotypes based on morphological traits under normal irrigation conditions, tiller number, 100 seed weight and Number of secondary spikelet traits, and in drought stress conditions, the number of filled grains in the panicle and panicle weight as the most important traits explaining variations seed yields. Comparison of path coefficients of yield and yield components showed that in normal irrigation conditions the number of tillers (0.652), however, under drought stress conditions; number of filled grains in panicle (1.513) had the most direct effect on yield. The highest correlation coefficient was observed in the number of filled grains in the panicle with grain yield (r = 0.931) under drought stress.

In general, IR64 genotype (susceptible control), under the influence of drought stress showed a significant decrease in yield and yield components (such as panicle length, panicle weight, number of filled grains in the panicle and percentage of panicle fertility percentage) than tolerant genotypes.