Analysis of heterosis for pod yield and its components in relation to genetic divergence of the parents and specific combining ability of the crosses in cowpea (Vigna unguiculata (L.) Walp.)

Manifestation of heterosis for pod yield and its four components, plant height/vine length, pods/plant, pod length, and pod weight, was examined in relation to genetic divergence of the parents and specific combining ability status of the crosses in a diallel cross of cowpea. Genetic divergence of parents was estimated by Mahalanobis D² statistic. Heterosis did not always occur in crosses between widely divergent parents, but in some crosses which involved much less divergent parents. It appeared that the frequency of heterotic crosses as well as magnitude of heterosis was much related to the specific combining ability status of the crosses. However, consideration of genetic divergence of the parents involved in the crosses along with positive sea status of the crosses would prove to be useful in predicting heterosis.