Estimation of combining ability and heterosis in snakegourd

Abstract

A diallel analysis in snakegourd iTrichosanthes anguina. L.) was carried out in the Department of Plant Breeding and Genetics, College of Agriculture, Vellayani during the period 1997-1999. The research work was taken up to assess the general and specific combining abilities, nature of gene action and also to estimate the heterosis for various characters. The six parents involved were selected from a previous D2 analysis conducted in the Department and were the most divergent ones. They are PI (Nedumangad local), P2 (Thrikkannapuram local), P3 (Kanhangad local - 3), P4 (Vlathankara local), Ps (Kaumudi) and P6 (Idukki local). The observations were recorded on yield and yield attributing characters. Significant differences were detected among the mean performance of the genotypes, for all the characters studied. The combining ability analysis revealed that the parent P, (Kaumudi) was the best general combiner for most of the yield and and yield contributing traits. The hybrids PI x Ps, P2 X P, and P2 x P6 were superior specific combiners in yield characters like mean weight of fruit, number of fruits per plant and fruit yield per plant respectively. The crosses involving P, and P6 were found to be good specific combiners for yield and yield contributing characters. The variance due to general and specific combining ability was significant in almost all the characters studied indicating the significance of both additive and non additive gene action in the characters. The sea variance was found to be more than gca variance in most of the characters studied indicating the predominance of non additive gene action. The ratio of additive to dominance variance was less than one in most of the characters again indicating the predominant influence of non additive

gene action which strongly substantiated the validity of the heterosis breeding method in improving the crop. Manifestation of heterosis was seen for all the characters studied. Among the hybrids, P2 x Ps had the maximum standard heterosis for yield and yield related characters. The crosses PI x Ps, P, X P(, and P3 x P, also exhibited significant standard heterosis for these characters. In general the hybrids involving the parent Ps was found to be more heterotic.