Genetic variability and heterosis in cucumber (Cucumis Sativus L.)

Abstract

The present investigation on (Genetic variability and heterosis in cucumber (Cucumis sativus L.)' was conducted at the College of Agriculture, Vellayani, Trivandrum during 1995-97. Twenty two genotypes of cucumber collected from different parts of the country were grown in randomised block design with two replications and assessed the genetic variability of fifteen characters. The genetic parameters like variability, heritability, genetic advance, correlation coefficients and direct and indirect effects of the component traits on yield were estimated. Seven parents were selected based on selection index, crossed in all possible combinations without reciprocals in a 7x7 diallel and produced 21 Fl hybrids. These F1 hybrids were evaluated along with their parents and derived information on general and specific combining ability and heterosis. Significant differences were observed among the 22 genotypes for all the fifteen characters studied. Yield/plant, fruits/plant, average fruit weight and node to first female flower had the highest genotypic coefficient of variation with high heritability and genetic advance. Fruits/plant, average fruit weight, fruit girth and fruit diameter were highly correlated with yield. Fruit girth exerted the maximum

positive effect on yield followed by average fruit weight and fruits/plant. Significant gca and sca variances were observed for all the traits. CS 12 and CS 9 were good general combiners for yield. The hybrids CS 12 x Punerikhira, CS 9 x ARC-1 and BSS 169 x ARC-1 possessed high sca effects for yield. Significant heterosis were observed for most of the traits. Relative heterosis, heterobeltiosis and standard heterosis were significant for days to first female flower opening. Punerikhira x ARC-1 and CS 9 x Punerikhira were significantly earlier than the standard variety CS 12. Relative heterosis and heterobeltiosis were observed for yield/plant. None of the hybrids exceeded the standard parent. The hybrids BSS 169 x ARC-1, CS 9 x ARC-l and Punerikhira x ARC-1 showed significant relative heterosis and heterobeltiosis for yield/plant.