Heterosis and Combining Ability in Pumpkin Inbreds (Cucurbita moschata Duch. ex Poir.)

Twenty hybrids along with five parents evaluated in the study were mainly contemplated to find out the best cross combinations and the best general and specific combiners as well as to estimate the nature and magnitude of the gene action for different qualitative traits. Using Griffings and Haymans approach through a 5 x 5 full diallel cross fashion, an investigation on heterosis and combining ability in pumpkin was undertaken following RCBD design with three replications at the experimental field. Both positive and negative significant GCA and SCA variances were obtained from few parents and hybrids. Predominance of additive-additive gene action was noted for most of the characters except hollowness and dry matter content, where additive-dominance gene action was predominant; flesh thickness and brix (%), where dominance-dominance gene action were predominant. A single parent was not found as good combiner for more than two characters. The best specific combiners were IBD 40 X IBD 47 for beta carotene, total sugar and fruit yield; IBD23 X IBD40 for brix (%), hollowness and flesh thickness; IBD40 X IBD57 for fruit breadth; IBD47 X IBD50 for non reducing sugar; and IBD47 X IBD57 for reducing sugar. The Vr-Wr graphs exhibited complete, partial and over dominance effect of genes for different characters. Complete dominance was observed only for beta carotene whereas over dominance was noticed for hollowness and flesh thickness. Partial dominance was ensured for fruit breadth, dry matter, brix (%), reducing sugar, non-reducing sugar, total sugar and fruit yield. Significant heterosis of some crosses against mid parent and better parents were observed for some characters.