GENETIC BEHAVIOR OF THE PHYSIOLOGICAL, NUTRIENT, AND YIELD TRAITS OF RICE UNDER DEFICIT IRRIGATION CONDITIONS

Given that water deficit is the main challenge to rice (Oryza sativa L.) production in Egypt, the development of drought-tolerant genotypes through classical breeding is the main strategy for increasing rice yield in Egypt. The present study aimed to generate new populations by crossing tolerant rice genotypes with local adapted cultivars. During 2019, seven rice genotypes were crossed in a half-diallel mating design to generate 21 F-1 hybrids. During 2020, the parental genotypes and their F-1 hybrids were grown and assessed with a randomized complete block design with three replications for chlorophyll pigments, antioxidants, nutrients, and yield components under water deficit conditions at Sakha Research Station, Kafr El-Sheikh, Egypt. General combining ability (GCA): specific combining ability (SCA) ratios were found to be less than unity for all studied traits, except for peroxidase (PA) activity. This result indicated the importance of nonadditive genetic variance in determining the performance of these half-diallel hybrids for various traits. Three rice parental genotypes, i.e., N-22, Azucena, and Giza-179, were identified as good general combiners for physiological and yield traits under water stress conditions. Under water stress conditions, the F1 hybrids Azucena x Giza-177, Sakha-104 x Giza-179, IRAT112 x Azucena, and Azucena x Giza-179 showed desirable SCA effects for the majority of the physiological and yield traits. The F1 hybrids Azucena x Giza-179, Azucena x Giza-177, Azucena x Sakha-104, N-22 x Giza-179, and Sakha-104 x Giza-179 demonstrated promising mean performance for chlorophyll pigment (a, b) and carotenoid content, proline content, catalase and PA activities, soluble sugar content, abscisic acid, and polyphenol oxidase, as well as grain yield and its components. These promising populations could be used in future breeding programs to develop drought-tolerant and high-yielding rice genotypes.