Heterosis and combining ability in Phaseolus aureus roxb

Heterosis and combining ability were estimated in F 1, F 2, F 3 and backcross generations of diallel cross in Phaseolus aureus. Hybrid vigour for yield compared with the mid-parent and better parent was noted in 21 and 20 F 1 hybrids, respectively. There was an appreciable amount of inbreeding depression in the F 2 and F 3 compared with the F 1 hybrids. Pod number seems to influence yield to a great extent. As expected, the high-yielding hybrids resulted from crosses between parents of diverse geographic origin. Combining ability analysis revealed that both g.c.a. and s.c.a. variances were important for yield, while g.c.a. variance was more important for seed size, pod number, cluster number and pods per cluster. The g.c.a. variance for yield appeared to be influenced by g. c. a. variances for yield components. In general, the crosses having high s.c.a. had one of the parents as high combiner for yield and other traits. The diallel study of different generations gave a comprehensive picture of combining ability.