Comparison of divergence analysis methods in Indian mustard (Brassica juncea L.) and its relationship with heterosis
2004
Ghosh, S.K. (Indian Agricultural Research Inst., Pusa, New Delhi. Div. of Genetics) | Gulati, S.C. (Vibha Agrotech Limited, Hyderabad (India))
Based on genetic diversity, 29 lines and 7 testers of Indian mustard genotypes were grouped into nine clusters using Mahalanobis D**2 statistic analysis following Tocher´s clustering and four diversity classes by divergence classification of Arunachalam and Bandopadhyay (1984). Divergence classification (DC) was carried out based on mean and standard deviation of D**2 values. In Tocher´s clustering, the most divergent parents are expected to express high heterosis, whereas DC method is more likely to bring out the maximum number of highly heterotic crosses from parents of intermediate divergence. A relative comparison of the two methods of diversity analysis was made and the relationship of heterosis with genetic diversity was studied. The Tocher´s method accounted for the cause of heterosis in 65% of the classes, whereas divergence classification reflected heterosis in 90%. Intermediate type parental diversity would also result in high heterotic F1 combinations. Results from the present investigation indicated that there is a close correspondence between genetic diversity and heterosis and it is important to ascertain the level of parental divergence for efficient hybridization based on these two complementary methods, for an efficient heterosis breeding programme. Divergence classification appears to be useful in identifying intermediate type of parental diversity that may help in exploiting economic heterosis. The study has also helped to identify three highly heterotic cross combinations namely, two through Tocher´s method (YSRL 10 x Pusa Bold and AD 2041 x Pusa Bold) and one exclusively through DC method (DBS 10 x Pusa Bold), which are suggested for further exploitation for improving yield potential of Indian mustard
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