COMBINING ABILITY ESTIMATES FOR SOME AGRONOMIC,YIELD COMPONENTS AND BLAST REACTION TRAITS IN RICE (ORYZA SATIVA L.)

Combining ability analysis was carried out in rice, through A 6 x 6 diallel set analysis (excluding reciprocals) for some agronomic and yield components traits as well as blast reaction at the Experimental Farm of Sakha Agricultural Research station, Sakha, Kafr El-Sheikh, Egypt during 2015 and 2016 summer seasons. The ratio of variances due to general and specific combining abilities (ó2 GCA / ó2 SCA) was found to be lower than unity for all studied characters, except 1000-grain weight, suggesting greater importance of non- additive genetic variance (over dominance or epitasis) in the
inheritance of these characters. Obviously, highly significant and positive estimates of (GCA) effects were recorded for chlorophyll content in Large stigma rice variety, indicating that this entry could be used to improve such trait. Regarding to blast reaction, the rice varieties; Giza 177, Giza 179 and Giza 178 exhibited significant and highly significant negative values of GCA effects, while Large stigma and Baldo varieties showed the positive values of GCA effects. The results proved that the rice variety Large stigma considered as good combiner for improving the earliness, shortness and high chlorophyll content. Also, estimates of GCA effects showed that the parents, Giza 177, Giza 178 and Giza 179 were found to be good general combiners for blast reaction. Moreover, Giza 178 and Giza 179 were the best general combiners
for grain yield/plant.
In addition, Blast reaction showed that five crosses were found to be high or highly significant and negative estimates of SCA, their estimated values were ranging from -0.70 for Giza 177 x Large stigma to -0.83 for Giza 178 x Large stigma. The crosses which gave negative significant values could be utilized in rice breeding program to improve this trait. Moreover, 5 crosses out of 15 combinations possessed significant desirable SCA effects for grain yield / plant involving two kinds of combinations between the parents of high x high GCA effects, such as SKC23819-192 x Baldo, suggesting that additive x additive type of gene action play an important role in the inheritance of thistrait.