Evaluation Of Combining Ability Of Sorghum Lines For Improving Hybrid Cultivar

Six male sterile with four male fertile sorghum, Sorghum bicolor(L.) Moench, lines were crossed in a factorial mating design in 1998. Twenty four F1 hybrids and ten parental lines were planted in a randomized complete block design in three replications, at Seed and Plant Improvement Institute, Karaj, Iran in 1999. Two cuttings forage were harvested from all genotypes (F12 and parents). Four traits including plant height, tiller no., green yield and dry matter were measured. There were significant differences among genotypes, cuttings and genotype X cutting interaction for all traits at 1% level of probability. Analysis of variance showed that, there are significant effects of genotypes, parent, parent vs. crosses (except for tiller no. at average of cuttings), lines (for plant height in 2nd cut and mean), testers and line tester interaction. There were differnces among lines and testers GCA which shows the importance of additive effects of genes for this traits, therefore, the selection methods can be used for breeding programmes. Heretiability of some traits were different in first, second and average of cuttings. Therefore, in each cutting, the heretiability should be considered in multi cutting sorghum lines. Significant differences were observed among SCA of some parents which shows the importance of dominance effects of genes for majority of traits in hybrids. Hence the hybridization method can be used for breeding programmes. The highest positive SVA was obtained for green fodder from crossing of A__ICS 84 × R__2 , A__ICS88005× R__1, A__ICS31×R__28 & A__1×R__112, and for dry matter from crossing of A__ICS88005×R__1, A__ICS__31×R__28, A__2×R__112, A__ISC84×R__112& A__ICS31× R__2 at average of two cutting. The highest yield of two cuttings was obtained for green fodder from crossing of A__ICS84×R__2 and for dry matter from crossing of A__ICS31×R__2 with 144.8 and 34.5 tha^-1 , respecticely.