Epistasis-Driven Bias in the Estimates of Additive and Dominance Genetic Variance in Dolichos Bean (Lablab Purpureus L.) Var. Lignosus

Abstract

The choice of suitable selection strategy for genetic improvement of any crop species hinges on the relative contribution of additive and non-additive components of genotypic variation of economic traits. Simplified triple test cross (STTC) design was used to detect epistasis and assess epistasis-driven bias in the estimates of additive (σ²_A) and dominance (σ²_D) components of genotypic variation of economic traits in Dolichos bean. The material for the study consisted of 12 genetically diverse inbred lines and two pairs of testers contrasting for economic traits. The 12 inbred lines were crossed to two pairs of testers in 2012 rainy season to generate two sets of STTC progenies, which were evaluated in 2013 and 2014 rainy season at the University of Agricultural Sciences, Bengaluru, India. The results indicated an important role of epistasis in inheritance of all the traits in Dolichos bean. While σ²_A predominated in the inheritance of racemes/ plant, σ²_D predominated in the inheritance of pod weight/plant. Only σ²_A was important in the inheritance of days to flowering and seed weight/plant. The 12 inbred lines used in the study contributed significantly to varying extent to epistasis governing different traits in both sets of STTC progenies in both years. The bias in the estimates of σ²_A was greater than that in the estimates of σ²_D. Therefore, it is not advisable to ignore epistasis in studies designed for determining the relative magnitude of σ²_A and σ²_D controlling target traits in Dolichos bean.

KEYWORDS:

• covariance of sums/differences
• direction of dominance
• narrow-sense heritability
• selection
• simplified triple test cross design