Combining ability analysis in complete diallel cross of waxy corn (Zea mays var. ceratina) for starch pasting viscosity characteristics

• The mean performance for pasting viscosity in waxy corn starches was significantly impacted by environments.
• Additive gene action was more important than non-additive gene action in determining pasting viscosity.
• Genotypes with high peak viscosity can be selected in early generations.

A complete diallel cross study of six inbred lines (KKU-BK, KKU-JP, KKU-UB, KKU-JD, KKU-G2 and KKU-N7) of waxy corn was carried out with parents and F1 progeny, to determine the combining ability of starch pasting viscosity characteristics across two environments in Thailand. The relative importance of additive vs. non-additive gene effects was determined. Analysis of variance for all parameters indicated highly significant differences among genotypes and genotype × environment interactions. The general combining ability (GCA) component of variance was significant for most traits, while specific combining ability (SCA) was significant for all of the pasting properties examined, but reciprocal effects were significant except for pasting temperature. Additive gene effects were most important only for peak viscosity; also, the magnitude of GCA variance was more pronounced than SCA variance for this characteristic. However, higher estimates of non-additive genetic variance were noticed for breakdown viscosity, final viscosity, setback viscosity and pasting temperature. Accordingly, the parents KKU-JP and KKU-UB used in this study appear to be suitable parents for use in breeding programs where improved pasting viscosity traits are desired.