GENETIC-DISTANCE AND HETEROSIS IN INDIAN MUSTARD - DEVELOPMENTAL ISOZYMES AS INDICATORS OF GENETIC-RELATIONSHIPS

The use of isozymes as indicators of genetic diversity and as markers for the selection of agronomic traits has been proposed in different c rop species. The present investigation was conducted to study the use of isozyme-derived genetic distance between parents in predicting the F-1 heterosis in Indian mustard. In addition, the interaction of isozy me-based diversity with quantitative trait and pedigree-based diversit y measures, and its role in predicting hybrid heterosis has also been examined. Sixteen Indian mustard lines and their 48 crosses (12 x 4, l ine x tester crossing) were evaluated over two environments for isozym e and quantitative morphological characters. The results from this stu dy suggest that the heterotic response to isozymic changes is more res ponsive in crosses derived from morphologically and pedigree-wise rela ted parents in comparison to crosses derived from unrelated parents. I t was possible to improve heterosis predictions by partitioning the is ozyme-based genetic distance into general genetic distance and specifi c genetic distance and correlating the latter with the specific combin ing ability of morphological traits. The possible reasons for these ob servations are discussed.