Abstract:
Combiningability study provides very useful genetic information about the ineheritance of
quantitative traits that helps to determine the type of breeding procedure to be employed
to improve the crop of interest. The objective of the study was to determine the type of
gene actions involved in the inheritance of the most important quantitative traits in
commercial white pea bean cultivars. Forty nine entries (7 parents and 42 F2 diallel
crosses) were grown in a simple lattice design with two replications at Jimma Agricultural
Research Center, South Western Ethiopia. The results revealed significant mean squares
in all of the characters, except for days to 50 % flowering, days to maturity, number of
nodes on the main axis, and internode length. There were significant mean squares due to
general combining ability, specific combining ability, reciprocal effects, maternal effects,
and non-maternal effects in almost all of the characters. The relative contribution of
specific combining ability was higher than general combining ability for all of the studied
traits, except for days to 50% flowering, pod length, and seed thickness.This indicating
that the non-additive gene actions are influential in the expression of these traits which
poses some difficulty as the non-additive gene actions are non-fixable. Thus, selfing
should continue for more generation to fix the non-additive gene actions before
undertaking selection. Significant general combining ability and specifi combining ability
effects were found for leaf rust and angular leaf spot, respectively. This indicates that
additive geneaction is important in the inheritance of rust and the segregating generation
can be improved by selection. Starlight is good general combiner for 100-seed weight and
grain yield. The other genotypes may also be good general combiner for other traits
because they displayed positive and significant traits.
