Heterosis breeding can be used to achieve improvement in quantity, quality, and productivity of pumpkin (Cucurbita moschata Duch. ex Poir.). A line × tester mating design was used to study standard heterosis for earliness, yield and yield related characters in pumpkin during 2009-2010. Thirty-six hybrids, developed by crossing 12 lines with 3 testers and a commercial check, 'MPH 1', were evaluated for earliness, yield and yield related characters and indicated presence of heterotic vigor. The hybrid 'Kasi Harit' × 'Avinashi Local' had negative relative standard heterosis for the node at which the first female flower appears, sex ratio, fruit number per vine, flesh thickness and total carotenoid content. Heterosis for days to appearance of the first female flower, days to first harvest, sex ratio, fruit number per vine, flesh thickness and total carotenoid content was in the desired direction in 'Vadhalagundu Local' ×'CO 2'. Estimates of standard heterosis for fruit yield indicated that hybrid 'Kasi Harit' × 'Avinashi Local' had the highest positive value followed by hybrid 'Vadhalagundu Local' × 'CO 2'. These hybrids had high heterosis for most component traits, can be used for exploitation of heterosis and released as promising hybrids after multi location testing.Heterosis is a genetic phenomenon and refers to expression of increased, or decreased, hybrid vigor over the mid-parent (relative heterosis), better parent (heterobeltiosis) and the best commercial variety (standard heterosis) in plant breeding. Hybridization to exploit heterosis commercially, or for selection of promising recombinants in subsequent generations, is the prime objective of heterosis breeding. Heterosis in cross-pollinated crops has the potential to increase yield. Superior recombinants identified in subsequent generations could be evaluated for commercial exploitation as cucurbits do not show inbreeding depression.The search for development of a quick and convenient way of combining desirable characters has assumed greater significance in production of F 1 hybrids in pumpkin (Cucurbita moschata Duch. ex Poir.). However, commercial usefulness of a hybrid would depend on its performance compared to the best commercial variety available. The monoecious character, conspicuous and solitary flowers, large seed number per fruit and wide variability for yield, size and shape of fruit make pumpkin useful for commercial breeding. Though several high-yielding varieties have been developed, the best potential can be achieved by developing hybrids with high yield, earliness and superior quality. A wide range of variability in vegetative and fruit characters is available in genotypes. However, little attention has been paid to its genetic improvement. Hybrid vigor can be substantially increased by crossing genetically diverse inbreds and heterosis obtained from genetic diversity among parents (Sharma, 1994). Previous research on pumkin by Mohanty (A c c e p t e d M a n u s c r i p t 3 3 (2002) heterosis, with different parents and hybrids, has dete...
