No abstract

Combining ability and heterosis for eight quantitative characters were studied through line x tester analysis involving five lines and four testers. The combining ability analysis revealed that variances due to hybrids, lines, testers and line x tester interaction were significant for all eight characters studied. The ratio of additive and dominance genetic variance (GA': oD) indicated that preponderance of non additive type of gene action for all the traits except number of branches per plant. The parents VGG 77, MI 267, Vamban 2 and KM 2 were found to be the best general combiners for most of the characters. The crosses with high sca effects were identified for each character. The hybrids ML 682 x Vamban 2 and VGG 77 x Vamban 1 recorded significant standard heterosis for all the traits except number of branches per plant. Three hybrids viz. K 851 x Vamban 1, VGG 77 x Vamban 1 and VGG 77 x KM 2 can be exploited in recombination breeding. Four cross combinations viz. ML 682 x Vamban 2, VGG 77 x Vamban 1, VGG 80 x KM 2 and ML 267 x Vamban 2 can be utilised for heterosis breeding.

Two varieties of sesame viz. SVPR 1 and CO 1 were treated with two mutagens viz. gamma rays and EMS. In M, generation, a wide range of polygenic variability in the form of micromutations was generated. M, generation shifted the overall mean values in the positive direction in lower doses upto 50 krad of gamma rays and 1.2% of EMS for the characters 1000 seed weight, oil content and single plant yield. Treated M, populations showed a much greater range of variability for all the characters than controls. Induced genetic variability was more in CO 1 than SVPR 1. The enhanced genetic variability observed for seed yield and its component characters in the M, generation of the present study indicated the scope for effective selection.

The effectiveness and efficiency of gamma rays and EMS in relation to chlorophyll mutations were studied in two varieties of sesame (Sesamum indicum L.) viz. SVPR 1 and CO1 in M, generation. Four types of chlorophyll mutants namely xantha, chlorina, striata and Xantha viridis were observed. Xantha viridis was observed in maximum proportion followed by chlorina and striata in both the varieties. Gamma rays was found to be more efficient and effective than EMS in both the varieties. The effectiveness and efficiency of both the mutagens was more in SVPR1 than CO 1.