Heterosis in relation to multivariate genetic divergence in brinjal (Solanum melongena)

The investigation was carried out during 2001-07 to examine the magnitude of heterosis in relation to genetic divergence among 9 parents in a 9 x 9 half-diallel cross of eggplant or brinjal (Solanum melongena L.). The 9 parents were grouped in 6 different clusters in the lot of 70 entries (10 elite varieties, 16 stable breeding lines and 44 indigenous cultivars of India and Bangladesh) based on multivariate analysis using Mahalanobis' D(2)-statistic employing 18 growth, yield components, fruit yield and fruit quality traits from three years evaluation. Diversity of these 9 parental lines was again determined separately based on 4 important characters including fruit yield. The relationship between intra- and inter-cluster divergence, total divergence of the parents and both relative heterosis and heterobeltiosis of 36 crosses for 4 important characters, viz plant height, fruits/plant, fruit weight, and fruit yield/plant, was determined using correlations and linear regression. It demonstrated positive relationship between genetic distance of the parents and both relative heterosis and heterobeltiosis for fruit yield/plant, however, the relationship was not strong enough for regression of heterosis on genetic distance to confidently predict the level of heterosis based on a given value of genetic distance between the parents indicating that there might be optimum level of genetic divergence between parents to obtain heterosis in the F, generation. It is suggested that reliance should also be placed on the genetic distance apart from combining ability while selecting the parents for hybridization in order to realize high frequency of heterotic hybrids in brinjal.