HETEROSIS AND INBREEDING DEPRESSION IN DRY BUSH BEANS, Phaseolus vulgaris L.

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Abstract
Heterosis and inbreeding depression in 13 crosses involving 10 dry bush bean, Phaseolus vulgaris L., lines and varieties are reported for days to maturity, pods per plant, 100-seed weight, seeds per pod, and bean yield. Six crosses showed positive heterosis (27.8–47.3%) over the mid-parent value for bean yield. Parents in each of these heterotic crosses differed for growth habit, seed size and geographical origin. But none of the F1 hybrids yielded significantly better than the highest yielding parental line. None of the crosses showed heterosis for pods per plant. All significant heterotic values for seeds per pod were negative. For 100-seed weight three crosses, both parents of which had small seeds, showed positive heterosis but one cross which had a significant negative value had one parent with small seeds and the one with large seeds. One heterotic cross each for bean yield and 100-seed weight showed subsequent inbreeding depression. But five crosses for bean yield, and one cross for 100-seed weight showing positive heterosis did not exhibit reduction due to inbreeding. Also, some crosses which either had nonsignificant or negative heterotic values for bean yield and yield components showed positive effects of inbreeding, i.e. the F2 outperformed the corresponding F1 hybrids. Possible causes for these phenomena are discussed.Key words: Bean, heterosis, inbreeding depression

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