ABSTRACT
Six Castor (Ricinus communis L.) accessories were crossed in 6x6 complete dialed to obtain 30 hybrids, and 6 parents. These 36 genotypes were used to estimate General Combining Ability (GCA) and Specific Combining Ability (SCA) effects for 50% days to germination, 50% days to flowering, plant height, peduncle length, number of racemes, number of branches, day to maturity, 100-seed weight and seed yield in order to select suitable parents for hybridization and to identify the promising hybrids. The 6 parents and 30 hybrids were evaluated in a randomized complete block design with three replications at the Institute of Agricultural Research (IAR) Zaria, in the dry seasons of 2009 and 2010 (two environments). General Combining Ability and Specific Combining Ability were estimated for 50% days to germination, 50% days flowering, plant height, peduncle length, number of racemes, number of branches, days to maturity, 100-seed weight and seed yield. The results revealed that mean squares for GCA and SCA highly significant for all the agronomic traits, indicating considerable amount of genetic variability in the germplasm which can be used to initiate selection for further improvement. Components of variance showed that the GCA variance was higher than the SCA variance for days to germination, days to flowering, days to maturity, number of branches, peduncle length, plant height 100-seed weight and yield. These results indicated that additive gene action was more important than non additive gene action for these traits. Accessories IAR CAS026 exhibited the highest positive GCA effects for yield, number of branches, number of racemes and highest negative GCA effects for days to flowering and days to maturity. VII Among all the crosses, IAR CAS 006 x IAR CAS 026 highest positive SCA effect for seed yield and IAR CAS 026 x IAR CAS 006 highest positive SCA effects for days to maturity and highest positive SCA effects for number of racemes. Thus, the two Accessories (IAR CAS 026 and IAR CAS 006) revealed good potential to be used as parents for hybrid
