Genetics Division, Indian Agricultural Research Institute, Pusa, New Delhi 110 012.
* Present address: Nagarjuna Agricultural Research and Development Institute, 45, Nagarjuna Hills, Punjagatta, Hyderabad 500 082.
In the present investigation, divergence classification - a method devised by Arunachalam and Bandopadhyay (1984) were used to classify the 36 mustard genotypes to draw a limit of parental diversity in expressing maximum heterosis. Mahalanobis D2 statistic was used to estimate genetic diversity (D2 values) and then the genotypes were classified into four divergence classes based on mean and standard deviation of all D2 values. According to divergence classification, DCI involved most distantly and DCIV the most closely related parents where as, DC II and DC III Involved the medium divergent parents. A scoring system was adopted to work out the relative order of importance of the divergence classes. The overall scores for each divergence classes based on significant and desirable heterosis (q) and mean (y) of such crosses for all characters were carried out to rank the divergence classes. According to the scoring system, the most desirable class would be with the lowest total score. Results clearly showed the superiority of classes DC III followed by DC II, as both the classes received low overall score and maximum number of heterotic cross combinations. In conclusion it can be said that divergence classification appears to be effective in clubbing the genotypes for parental diversity and suggested that parents with intermediate diversity would be used to produce heterotic cross combination.
Brassica juncea, Indian mustard, D2 statistic, parental diversity, divergence classification
