GENETIC BEHAVIOR AND COMBINING ABILITY FOR SOME TRAITS OF ROOT, PHYSIOLOGICAL AND GRAIN QUALITY TRAITS IN RICE UNDER WATER STRESS CONDITIONS

Eight local and exotic cultivars of rice were crossed to obtain 28 F 1 crosses, through half diallel mating design. Griffing 1956 Method 2, Model 1 was employed for this purpose. The eight parents and their 28 F 1 s ( excluding reciprocals) were grown in a randomized block design with three replications at RRTC Farm, Sakha, Kafr El-sheikh, Egypt. Data were collected on seven root, agro- physiological and grain quality traits under both normal and water deficit conditions. GCA and SCA were significant for all the studied traits under both water deficit and normal conditions. GCA\SCA ratios were found to be greater than unity for root length and grain length traits under water deficit conditions and grain length under normal conditions. This finding indicates that additive and additive x additive types of gene action were of greater importance in the inheritance of these traits. On the other hand, GCA\SCA ratios were found to be less than unity for the rest of the studied traits, indicating that the non-additive type of gene action including dominance was of great importance in the inheritance of these traits. The estimates of gca effects indicated that parents, Balado and Wab 878 were good combiners for amylose content under both normal and water stress condition. The parent Wab 450 was a good general combiner for root length, root volume and chlorophyll content. In addition, Gaori and GZ 1368 were the best combiners for root/shoot ratio and milling %. Sakha 104 was a good combiner for only milling %. Moreover, The cross combinations, Sakha 102 X GZ 1368, Wab 450 X Gaori and IET1444 X Gaori appeared to be the best ones for root length and root volume since it exhibited a significantly positive sca effect and some of them involved parents with high gca under water stress condition. Moreover, the cross combinations, Sakha 102 X Gaori, Sakha 104 X IET 1444, IET 1444 X Wab 878 and IET 1444 X GZ 1368 exhibited high sca and included at least one parent having good gca for milling % under water stress condition. Results further indicated that 19. 7 and 8 crosses had significant positive better parent heterosis for root volume, root/shoot ratio and chlorophyll content under water stress condition, respectively. Mid-parents heterosis expression in milling % did not show consistency over the studied condition, indicating character x environment interaction. Moreover, highly significant negative estimates of heterosis mid parent were recorded in Sakha 102 X Balado, Sakha 102 X Wab 878, Sakha 104 X Wab 450, Balado X Gaori, Balado X GZ 1368 and Wab 450 X IET 1444 rice genotypes for grain length under both conditions. On the other hand, IET 1444 X Gaori rice hybrid exhibited either highly significant positive estimates of heterosis for root volume, root/shoot ratio or negative for amylose content %. The phenotypic correlation coefficients were found to be highly significant positive between root length and each of root volume, root/shoot ratio and chlorophyll content %. Root volume was phenotypically associated with root/shoot ratio and chlorophyll content %. Moreover, chlorophyll content was correlated with root/shoot ratio. Regarding grain quality traits, grain length was significantly and positively correlated with milling % and amylose content % under both conditions