Resumo

SANCHEZ-HERNANDEZ, César et al. Combining ability effects in summer squash hybrids type Grey Zucchini. Rev. Chapingo Ser.Hortic [online]. 2011, vol.17, n.2, pp.89-103. ISSN 2007-4034.

Eight commercial hybrids of summer squahs type 'Grey Zucchini' (Cucúrbita pepo L.) and their 56 possible crosses of a diallel using the Method I Model II of Griffing (1956) were evaluated in Chapingo Mexico, during 2007 and 2008; to identify the best combinations among the commercial hybrids according to the general combining ability (ACG) and specific combining ability (ACE) effects; and to begin a genetic improvement program to get squash synthetic varieties. The experimental design used was a randomized complete block with three replications. The experimental plot consisted in two rows of 5 meters, with row separation of 0.80 m and 0.2 m between plants (62,500 plants-ha^-1). The combined analysis showed that dominance effects for the main components of the yield: fruit per plant, yield per plant and hectare were more important, and number of days to female flowering additive effects were important and make it feasible to improve precocity. From the best six crosses for squash fruit yield, three of them could only be used as hybrids (ACG < ACE): Hurakan x Lolita (52.16 t·ha^-1); Lolita x Tala (50.14 t·ha^-1); Tala x Terminator (47.72 t·ha^-1); two as synthetic varieties (ACG > ACE): WA9041 x Lolita (51.45 t·ha-1); Grey Zucchini M+M x Terminator (50.00 t·ha-1) and one as a base population to be improved by recurrent selection, since the additive and of dominance effects are important (ACG = ACE): Lolita x Terminator (44.09 t·ha^-1).

Palavras-chave : Cucurbita pepo L.; general combining ability; specific combining ability; maternal effects; reciprocal effects.