Genetic analysis of mode of inheritance of seed yield and its components in tropical soybean genotypes

Abstract

The decision related to efficient breeding methods depends largely on the understanding of the type of gene action controlling the expression of the characters to be selected. The objective of this study was to estimate the gene action controlling yield and components in soybean (Glycine max L. Merrill). The study involved six basic soybean generations (P1, P2, F1, F2, BC1 and BC2) of two crosses, i.e. cross I (TGx1987-62F × TGx1830-20E) and cross II (TGx1987-10F × TGx1740-2F), at the Research farm of the International Institute for Tropical Agriculture, IITA, Ibadan. Data were subjected to generation mean analysis to determine gene actions and interactions, using Hayman model. The results obtained from the individual scaling test A, B, C indicated that the simple additive-dominance model was inadequate to reveal the inheritance of the gene governing most traits. Non-allelic gene interaction was crucial in the inheritance of most studied traits. The Hayman six-parameter genetic model demonstrated that the signs of [h] and [l] were contrasting for most of the traits; suggesting duplicate epistasis. In fact, the effect of dominance was important and significant in the genetic control of most of the traits studied. Therefore, improvement of soybean seed yield and its related characters need intensive selection and should be delayed until later generations.