To predict the behaviour of selections in the F 1 generation itself before taking them to the advanced generations for further screening, the applicability of diallel cross analysis was studied .For this purpose four N. tabacum varieties were crossed in all combinations to constitute a diallel system and data collected on green leaf, saleable leaf i .e . sum of bright leaf and medium leaf yields, number of days taken for flowering, length and breadth of the middle leaves at maturity of the F l plants were subjected to JINKS and HAYMAN method of analysis .The results showed that Delcrest is a good combiner in throwing better recombinations . It always improved the yielding potential of the poorer parent . In the light of the graphical analysis, the results were discussed in relation to the improvement of the crop and predictions made as to which cross throws better strains . The characters studied are mostly additive in gene action . The scope of this method in the breeding projects to evolve superior strains was outlined .
A study was made on the quantitative inheritance of seven characters viz ., flowering time, plant height, leaf length, leaf width, number of curable leaves, green weight and cured weight for two crosses of flue-cured tobacco Chatham x Delcrest and 232 x Hicks. Six genetic populations P1, P2, F1, F2, B1 and B 2 were observed in each cross.Small and significant values of heterosis were observed for almost all the characters for the two crosses . Significant average inbreeding depression was found for all the characters in both the crosses.Significant additive and dominant effects were found for the various characters in the cross Chatham x Delcrest in which the dominance gene effects were high . While in 232 x Hicks cross, additive gene effects contributed much in controlling the characters studied.Significant epistatic effects were found for leaf length and number of leaves in the cross Chatham x Delcrest, flowering time and plant height in 232 x Hicks by x 2 test . Indications of exploiting these above two characters in plant breeding were revealed by these studies and a systematic approach in planning for such exploitation would be possible by further investigations .
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