Improving Rice Genetic Resources by Conducting Differential Crossings to Create New Hybrids in Both Regular and Water- Deficient Conditions

Thirty-six genotypes (8 parents and 28 F1s excluding reciprocals) were grown in a randomized complete block design (RCBD) with three replications at the Rice Research experimental farm, Sakha, Kafr El-Sheikh, Egypt, in 2022 and 2023 seasons. The ratio of GCA and SCA variances was greater than one for most of the studied traits, suggesting that additive and additive x additive types of gene actions were more significant in the inheritance of these traits. The genotypes IET1444, Wab880 SG 33 and Sakha107 were identified as the top general combiners for most of the studied traits. The crossings Wab880 SG 33 × IET1444 and IRAT112 × ARS.105-2-1-1-2 were identified as the most effective cross combinations for various root characteristics in conditions of water deprivation. The crossovers Wab880 SG 33 × IRAT112 and Sakha107 × IRAT112 were identified as the most effective cross combinations for the majority of agro-physiological attributes in conditions of water deficit. Giza177 × IRAT112 and Sakha107 × ARS.105-2-1-1-2 were identified as the most effective cross combinations for yield and its components traits under both situations, these crosses exhibited considerable and high Specific Combining Ability (SCA) in a favorable direction particularly under water stress conditions. Wab880 SG 33 × IRAT112 exhibited significant and favorable estimates of heterosis and heterobeltiosis for root and agro-physiological traits. Sakha107 × ARS.105-2-1-1-2 indicated the same for yield and its components traits in both situations.