Gene action and heritability of leaf and reproductive characteristics in soybean

Soybean [Glycine max (L,) Merr,] cultivars with smaller area and lanceolate leaves have shown better light distribution through their canopy and a hig her photosynthetic rate than those with larger leaf area and oval leaf shap e, However, very little information has been published about leaf character istics in relation to yield potential and inheritance which would assist br eeding effects to develop new cultivars with optimum leaf area and leaf sha pe. Gene action and heritability for leaf area, leaf shape, and other repro ductive characteristics were studied in a diallel cross including nine pare nts with large, medium, and small leaf area. Most progenies from crosses am ong parents with different leaf areas had larger mean leaf area, longer flo wering, and later maturity than the midparent and both parents, suggesting transgressive segregation for these traits. General combining ability (GCA) and specific combining ability (SCA) for leaf area and leaf shape were sig nificant in populations, Ratios of GCA to SCA were 0.96 for leaf shape and 0.89 for leaf area, indicating that GCA effects were more important than SC A, Genetic gain for leaf area and shape may be possible through selections. Narrow sense heritability estimated on the basis of variance components wa s 43.4% for leaf area, 63.2% for leaf shape, and 29.1% for maturity, which were lower than days to flowering and flowering period due to large error v ariances (sigma(2)E) caused by field environmental factors, This study indi cated that it is possible to optimize leaf area and leaf shape related to p hotosynthetic rate and subsequently yield, because of relatively large and significant GCA effects for these traits, The predominance of additive effe cts should improve the effectiveness of selection based on performance of i ndividual cultivars.