The importance of vegetative traits due to the bio mass during early stages which transform to dry mater at late stage. So, the investigation was undertaken to determine the combining ability effects, heterosis and genetic parameters for some vegetative traits. Egypt during 2018 and 2019 growing summer season. Four of the most important local varieties and lines; Sakha 101, Sakha 104, and GZ 9461-4-2-3-1(leaf blast susceptible) and Giza 178 (leaf blast resistant) used as lines and 4 testers contain resistance genes. They are IRBL 7-M, IR12N245, IR12G3239 and Sakha Super300 in Line X Tester design mating design was conducted and 16 F1 hybrid combinations were developed from the crossing between 4 lines and 4 testers. The data recorded on five vegetative traits showed highly significant differences among genotypes; parents, parents vs. crosses , crosses, lines, testers and line × tester for all studied vegetative traits. The estimates of the variance, ratio of general and specific combining ability and degree of dominance indicated preponderance of non-additive gene effect for each trait. Within lines; GZ 9461-4-2-3-1 recorded the best general combining ability effects (GCA) for most of the studied characters. Among testers; IR12G3239 and Sakha Super300 were observed to be good general combiners for most of the studied characters . The cross Sakha101 x IR12G3239 was observed to be good specific cross combinations for the most studied traits due to highly significant specific combining ability effects (SCA) and heterotic effects. High broad and narrow sense heritability estimates were observed for most traits. Correlation estimates revealed that plant height correlated positively and significantly with each of number of tillers per plant and leaf blast reaction to indicate the importance of selection for semi dwarf genotypes.
during 2018 and 2019. Four of the most important local varieties and lines were selected for yield and quality,i.e, Sakha 101, Sakha 104, and GZ 9461-4-2-3-1 and Giza 178 were used as lines and 4 testers. They are IRBL 7-M, IR12N245, IR12G3239 and Sakha Super300 in Line X Tester mating design. Sixteen new combinations developed from crossing four lines by four testers were assessed for the extent of combining ability effects, heterosis and genetic parameters for yield and related traits. The data recorded on seven yield characters showed highly significant differences among genotypes; parents, parents vs. crosses, crosses, lines, testers and line × tester for the yield and its components. Estimates of the variance, ratio of general and specific combining ability and degree of dominance indicated the importance of non-additive gene effect for all studied traits. Within lines; Sakha 101, GZ 9461-4-2-3-1 and Giza 178 recorded the best general combining ability effects (GCA) for most of the studied traits. Among testers; IR12G3239 and Sakha Super300 were observed to be good general combiners for most of the studied characters. The cross combinations of GZ 9461-4-2-3-1 x IR12G3239, Giza178 x IR12G3239 and Sakha101 x IRBL 7-M were observed to be good specific cross combinations for grain yield and most of its related traits due to highly significant specific combining ability effects (SCA) and heterotic effects. High broad and narrow sense heritability estimates were observed for most studied traits. Correlation estimates revealed that yield per plant correlated positively and significantly with each of number of panicles per plant, panicle length, panicle weight and number of filled grains per panicle.
Developing hybrid rice by two lines system under Egyptian conditions requires high performance lines. The promising Photoperiod and Thermo-sensitive Genic Male Sterile (PTGMS) lines A001S and G001S were developed by crossing, continuously inbred for six generations,and the selection depended onduration and tillering ability. F2 populations were segregated and fitted well to the ratio of 15:1 for pollen grains fertility trait, indicating the presence of digenic inheritance and epistatic dominant duplicate gene action control. The PTGMS line G001S had the most desirable characteristics for the hybrid rice breeders, with values of 19cm panicle length,13 primary branches panicle -1 , 8.5mm grain length, 2.9mm grain width, 1.9mm grain thicknessand 25g for 1000-grain weight. Both A001S and G001S were superiors of most studied traits to be good PTGMS lines for two-line hybrid seed production systems. Both linesexhibited a high rate of panicle exertion with values of 90.70 % and 94.30 % for A001S and G001S, respectively. The two lines were completely male sterile when sowing from 1 st to 20 th April. Still, their fertility alternated from completely sterile to partially fertile in late July when the temperature decreased and the day length was long. A001S x GSR1 and G001S x GSR9 new hybrid combinations were derived from the newlydeveloped PTGMS lines; A001S and G001S, with short duration, semi-dwarf and high tillering ability with a high yield potential of 80gplant -1 . For the panicle and grain traits, both hybrids exhibited good characteristics.Both hybrids showed favorable positive significant, and highly significant standard heterosis.
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