Genetic analysis in ivygourd (Coccinia grandis (L) viogt)

Abstract

The present investigation entitled "Genetic Analysis in Ivygourd (Coccinia grandis (L) Voigt.) was conducted at the Department of Plant Breeding and Genetics, College of Agriculture, Vellayani during 1999-2001. Objective of the study was to estimate the genetic basis of different characters, genetic divergence in the germplasm and to formulate a selection index for identifying superior types. The material for the experiment was 90 different local cultivars collected from different agroclimatic regions. The data for the investigation were collected from two field experiments, each laid out in Randornised Block Design with three replications. In Experiment I a collection of 50 genotypes of ivygourd was grouped into 11 clusters using Mahalanobis D2 statistic and based on eight morphological characters. Five genotypes Kuriyabandar local I, Kuriyabandar local Ill, Pilangatta local 11 & III and Kudlu local I, could not be grouped with others and so are kept as independent clusters. The cluster C IX was found to have maximum intercluster distance with seven of the eleven clusters formed. This was followed by C 11 which showed maximum divergence with four out of the eleven clusters. The results suggest that selection of parents from these divergent clusters will be effective in future hybridisation programme. The three superior crosses identified were Balthangadi local I x Pilangatta local 11, Bandargrarn local I x Pilangatta local 11 and Seetharnbeta local I x Pilangatta local II. Number of flowers per plant and number of leaves per plant were found to be the two characters that contributed maximum for the divergence of the genotypes. So both at phenotypic and cluster levels, these two characters can be considered as potential contributors of differentiation in Jvygourd. In Experiment II the data collected from 40 genotypes of ivygourd were subjected to analysis of variance and the genetic parameters like variability, heritability; genetic advance, correlation coefficients and path coefficients were estimated. Based on the above observation, a selection index was also formulated. Significant genotypic differences were observed among the 40 genotypes for all of the sixteen characters studied. High genetic variability was expressed by the characters fruit yield per plant, number of fruits per plant and number of flowers per plant. High heritability along with a good genetic advance was found for all the characters studied, except for number of days for first flower opening which exhibited high heritability and low genetic advance. These results indicate that the selection of plants which are phenotypically superior with respect to fifteen of the characters studied will certainly result in a significant improvement in the next generation. The genotypic correlation coefficients were higher than the corresponding phenotypic and environmental correlation coefficients revealing the fact that phenotypic expression of these correlations are reduced due to the influence of the environment. Yield per plant exhibited positive association with all the characters except number of days for flowering, which had significant negative correlation with yield. Number of fruits per plant and single fruit weight were the characters with high direct and indirect effects. Based on the above results, a selection index was formulated and local cultivars of Alappuzha, Kanjangad, Thirunelli, Mancheswararn and Nangikadapurarn were identified as the five top ranking genetically superior ivygourd genotypes. To sum up, the results of the present study indicates that being strictly a cross pollinated crop with possibility for vegetative propagation, methods of breeding which can. be successfully followed are individual plant selection, mass selection to improve varieties, pedigree method and heterosis breeding and vegetative propagation of the heterotic combinations. Considerable variability of the crop has been observed in Kamataka, Andhra Pradesh, Tarnil Nadu and northern parts of Kerala. There is considerable scope for survey, collection and maintenance of germplasm. The study highlights the feasibility of producing commercially viable indigenous selections and hybrids which are early, producing more number of bold and tender fruits with good storability and resistance to pest and diseases.