INHERITANCE OF SEED YIELD, MATURITY AND SEED WEIGHT OF COMMON BEAN (PHASEOLUS-VULGARIS) UNDER SEMIARID RAIN-FED CONDITIONS

To develop an effective breeding programme for rainfed production of t he common bean (Phaseolus vulgaris L.), the inheritance of seed yield under such conditions should be understood, preferably considering the effects of environment to account for site or season specificity. Thu s, heritability, expected and realized gain from selection, and combin ing ability were evaluated for a nine-parent diallel of common bean wi thout reciprocals but including parents, at two locations each in Mexi co and Colombia, using the F2 and F3 and F3 population bulks. Heritabi lity estimated from regressions of F3 on F2 ranged from 0.09 +/- 0.18 (S.E.) to 0.75 +/- 0.25 for seed yield, from 0.26 +/- 0.09 to 0.34 +/- 0.09 for days to maturity and from 0.57 +/- 0.04 to 0.80 + 0.04 for 1 00-seed weight. Expected gain from selection in the F2 was estimated a s a percentage of the population mean, selecting the upper 20% of the populations. Expected gain in seed yield ranged from 1.8 to 8.4 % in M exico and from 6.5 to 28.1 % in Colombia. Realized gains in seed yield in the F3 were 0.4-7.4% in Mexico and 2.9-15.7% in Colombia. Realized gain values for days to maturity were < 2.2 %, and for 100-seed weigh t > 13.4 %. General combining ability (GCA) mean squares (estimated us ing Griffing's Method 2, Model 1) were significant (P < 0.01) and larg er than those for specific combining ability (SCA) for all traits at a ll locations. The parents from the Mexican highlands tended to have a positive GCA effect for yield in Mexico but negative values in Colombi a, whereas parents adapted to mid-elevation tropical environments show ed the opposite tendency. However, all significant GCA values of breed ing line V8025 were positive in both countries.