Studies on genetic analysis in snake gourd (trichosanthes anguina l.)

An investigation entitled “Heterosis breeding in snake gourd (Trichosanthes anguina L.)” was carried out in the Department of Horticulture, Faculty of Agriculture, Annamalai University, Tamil Nadu, India during 2003-2007. The parents from diversified genotypes and their hybrids in snake gourd were evaluated for fruit yield per plant, yield attributing characters and quality traits with the objective of analyzing gene action. The characters observed were days to first male and female flower opening, number of fruits per plant, fruit length, fruit girth, flesh thickness, single fruit weight, fruit yield per plant, number of seeds per fruit, Vitamin C and acidity content of fruit. Based on the per se performance with specific trait and genetic divergence from different clusters, six genotypes namely P1–Hessaraghatta local (Bangalore, Karnataka), P2–Ottanchathiram local (Dindigul district, Tamil Nadu), P3–IC-212484, NBPGR, Trichur, P4–Michaelpalayam local (Dindigul district, Tamil Nadu), P5–PKM–1 (mutant variety, HC&RI, TNAU, Periyakulam), P6–Vellayani local (Kerala) were selected for crossing in full diallel programme. The analysis of variance indicated that the selected six parents and their 30 hybrids differed among themselves for all the eleven traits studied. Degree of dominance indicated that the traits viz., days to first female flower opening, fruit girth, number of fruits and fruit yield per plant and Vitamin C content of fruit were controlled by over-dominance. The remaining traits were controlled by partial dominance. The positive and negative signs of F and the ratio of H2/4H1 implied that the frequencies of positive and negative alleles in the parents were asymmetrical. All the characters were governed by single group of genes. The narrow sense heritability estimates were high for all the traits except Vitamin C content of fruit. It indicated that all the characters except Vitamin C content have exploitable additive genetic variances. The present study revealed the preponderance of additive gene effects followed by non fixable dominance gene effects in most of the crosses and in almost all the traits studied. As snake gourd is being highly cross pollinated crop, heterosis breeding is an ideal tool to improve fruit yield per plant.