Resumen
- The diallel analysis was used mainly to estimate general-(GCA) and specific combining ability (SCA) effects for a fixed sample of parents and less frequently to estimate components of variance for a random sample of parents of the reference population. In both cases, only additive and deviations due to dominance effects can be estimated, assuming that epistasis is negligible. The triallel analysis allows the estimation of epistasis variance because more ancestors are available and more covariances among relatives can be estimated. The maize population SA-8 was used to estimate components of variance through the generation of single- and three-way crosses with a random sample of 50 S1 lines. Replicated trials were planted in ten environments, including seven acidic and three non-acidic soils. Each trial consisted of 400 entries, 100 single- and 300 three way-crosses. Yields on non-acidic soils averaged 70% greater than on acidic soils. Within a given soil type (non-acidic or acidic), single crosses were similar to three-way crosses in overall mean, highest, and lowest values for grain yield, days to 50% silk emergence, and plant height. For these traits, GCA and SCA sum of squares were highly significant using the triallel and diallel analyses for acidic soils, and across environments; although an overestimation for GCA effects for the diallel analysis was observed. Estimation of components of variance using the triallel and diallel data for the full model showed that σ2AD, and σ2AA explained 79 and 19% of the genetic variance, respectively, and both were highly significant; σ2A explained less than 2% of the genetic variance. On the other hand, using the reduced model, σ2A and σ2D were significant and explained 37 and 63% of the genetic variation, respectively. The results, using the diallel data only, are in agreement with the reduced model. These results suggest that epistasis was important in the SA-8 maize population. The similar grain yields for single- and three-way crosses in the present study suggest that both types of hybrids would be suitable to increase maize yields in acidic and non-acidic environments of the developing countries.