Herança da senescência retardada em milho / Inheritance of the delayed senescence trait in Maize

AUTOR(ES)
DATA DE PUBLICAÇÃO

2007

RESUMO

Information on the inheritance of traits to be selected is of paramount importance for the success of breeding programs. The trait delayed senescence, usually named "stay-green" trait, has been related to tolerance to abiotic stresses, mainly drought stress, in several crop species. Although the majority of commercial maize hybrids are "stay-green", limited information are available on its inheritance. Thus, this research was conducted to study the inheritance of the stay-green trait in tropical maize. The genetic material included 55 inbred lines from several sources to represent the genetic variation of tropical maize. Fifty inbred lines were crossed to 05 inbreds as testers following the partial diallel cross design, giving rise to 250 single crosses. The crosses and six commercial hybrids, 256 entries, were evaluated at eight environments using a 16 x 16 lattice design with two replications per environment. The stay-green trait was recorded 120 days after sowing, in five competitive plants per plot, following a visual note scale, i.e., from 1 to 5, where 1 refers to green plants and 5 to no-green plants. Also, the trait days to mid-silking was recorded and used as covariate to correct for differences of maturing among crosses. The analysis of variance of the diallel crosses was computed following the method 4 model 1 of Griffing (1956) extended to multiple environments. The general combining ability (GCA) for both the inbreds and the testers, and the specific combining ability (SCA) were all highly significant (P<=0.01), showing that GCA as well as SCA contribute significantly for the expression of the trait. However, the contribution of the GCA was 69.06% and of the SCA was 30.94% for the variation among the crosses, indicating that the additive effects, which are related to GCA, are more important than the non-additive effects (dominance and epistasis), which are related to SCA, for the variation of the crosses. Both GCA and SCA interacted significantly with the environments, showing that these parameters were not consistent across the environments. Thus, selection for the stay-green trait should be based on the means of experiments evaluated in several environments.

ASSUNTO(S)

seleção genética. stay-green expressão gênica delayed senescence combinação genética milho maize cruzamento vegetal specific combining ability. general combining ability linhagens vegetais hereditariedade

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