The Response of Genetic, Morphological, and Biochemical Parameters of Rice (Oryza sativa L.) F2:4 Genotypes to Drought Stress at the Germination Stage

Rice is one of the oldest and most important cereals in the world and is a desirable model plant for genetic and molecular studies. Drought is one of the important risks for the successful production of crops, especially rice, in the world, which can be created at any time during the growing season. One of the main challenges in agriculture is to produce more food with less water consumption, and therefore, the production of rice genotypes that can have more tolerance to drought stress is one of the main goals of breeding projects.

In order to evaluate the effect of drought stress (zero (control), -3 and -5 bar using Polyethylene Glycol) on some genetic, morphological, and biochemical characteristics of rice at the germination stage, 38 lines with their parents (MousaTarom and 304) were investigated in randomized complete block design with three replications during 2022.

Morphological traits were decreased under -5 bar drought stress compared to the control. The germination rate and percentage were increased by 9.6 and 1.1% under -3 bar stress, and 37.8 and 33% under -5 bar stress, respectively. The rootlet length, rootlet fresh weight, and dry weight increased under - bar stress compared to the control, indicating that the rice plant can tolerate such a stress intensity, and it may even be used as a priming. Catalase, peroxidase and superoxide dismutase enzyme activities increased by 59, 51 and 81%, respectively, by increasing the stress to -5 bar compared to the control. This increase shows the increase of the plant's resistance to the active oxygen and drought tolerance. The highest phenotypic correlation in non-stressed conditions was between seedling weight and length vigor (0.92), under -3 bar stress was detected between shootlet length and fresh weight (0.91), and under -5 bar stress the highest one was between seed germination percentage and rate (0.94). The factor analysis for each of the zero, -3 and -5 bar drought stress levels introduced three factors that explained 73.68, 81.13 and 81.73 percent of the variance, respectively.

The high diversity of traits at the -5 bar drought stress indicates that it is possible to use germination rate and percentage, length and weight indices, and shootlet length and fresh weight as criteria for genotype selection under -5 bar drought stress. Such traits could be used as effective ones in the selection of tolerant rice genotypes at the germination stage and in order to establish the rice plant optimally.