Estimates of Combining Ability and Cluster Analysis for Some Rice Vareities (Oryza sativa L.)

The present study was carried out during 2009 and 2010 growing seasons at Rice Research and Training Center (RRTC) Farm, at Sakha, Kafr El-Sheikh Egypt. Eight Egyptian genotypes i.e., five commercial varieties (Giza177, Sakha101, Sakha104, Sakha105 and Sakha106), one promising lines (Gz 7576-10-3-2-1) and two international deferential varieties (BL1 and Shien2). The eight genotypes were sown in the summer growing season of (2009) in three sowing dates. A half diallel design was conducted among the eight parents to produce twenty eight crosses. Eight genotypes and their 28 hybrids were studied for nine traits e.i, plant height, No. of days to heading, No. of panicles plant^-1, grain yield plant^-1, 1000-grain weight, spikelets fertility%, hulling%, milling% and head rice%. The mean square of genotypes, parents, crosses and parents vs. crosses revealed highly significant variations for all traits under investigation. Both general combining ability and specific combining ability variances were found to be highly significant for all studies traits. The GCA/SCA variance were found to be greater than unity for No. of days to heading and 1000-grain weight, indicating that, additive and additive × additive types of gene action were of greater importance in the inheritance of these traits but the another studied traits the non-additive type were great important in plant height, No. of panicle plant^-1, grain yield plant^-1, spikelets fertility%, hulling%, milling% and head rice%. The five rice varieties Sakha105, Sakha106, GZ7576-10-3-2-1, BL1 and Shien2 showed highly significant negative GCA effects for No. of days to heading, while Giza177, Sakha101 and Shien2 exhibited significant negative GCA effects (desirable) for plant height. Sakha 101 exhibited highly significant positive GCA effects for No. of panicles plant^-1. The two rice varieties Sakha101 and Sakha104 which proved to be excellent combiners for grain yield plant^-1 would be of practical interest in a breeding program towards developing high yielding genotypes. Fourteen out of the twenty eight hybrid combinations showed highly significant negative SCA effects for No. of days to heading. Twenty out of the twenty eight F₁ hybrids exhibited highly significant desirable SCA effects for grain yield plant^-1. These superior twenty crosses were previously found to express useful heterosis. Clustering varieties based on similarity of quantitative characters produced tow large groups. The first group, included Sakha 101 and Sakha 104 these two similar varieties in heading average was 107.5 days. The second group included all short days to heading, the average of those varieties was 91.6 days.