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Genetic control of flowering in determinate soybean genotypes under diverse photoperiods

José Francisco Ferraz de Toledo; Cláudia Triller; Luciane Taviano Donato; Marcelo Fernandes de Oliveira; Angela Cely Tsutida

Centro Nacional de Pesquisa de Soja, CNPSo, EMBRAPA, Caixa Postal 1061, 86001-970 Londrina, PR, Brasil. Send correspondence to J.F.F.T.

ABSTRACT

Four soybean parents, including three with a classical type of response to photoperiod (BR85-29009, FT-2 and BR-13) and one long juvenile trait carrier (OC-8), were crossed in all combinations, including reciprocals, to obtain six sets of F2, F3 and F7 generations. The flowering response to photoperiodic variation and the genetic mechanisms controlling this response were studied. Day length variation was obtained by sowing the materials from September to December at Londrina, Paraná (23^o22'S latitude). The genetic models fitted to the means and variances of the generations indicated the predominance of additive effects controlling days to flowering. Significant dominance, epistasis and genotype x environmental effects were detected. No particular model was found to be associated with crosses where one of the parents was a carrier of the long juvenile trait. The predominant response of F7 lines to day length changes depended on the cross. Genes controlling classical and long juvenility combined freely; all crosses produced F7 individuals with classical or late flowering under short day conditions response to photoperiod. Intermediate responses between the typical classical and typical long juveniles were also observed in all cases. Such responses are only possible through the recombination of various genes of a single system.

Keywords: genetic control; flowering; soybean genotypes; photoperiods.

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