Better understanding breeding values and their combining ability of favored traits is essential to identify potential parents and hybrids. Our study utilized shrunken (sh2) sweet corn (Zea mays L.) parental lines and their derived hybrids, where the parental lines have undergone long-term selections to improve adaptation, yield, and eating quality under the tropical savanna of Thailand. We aimed to estimate heterosis, combining ability, and gene action for agronomic traits and kernel carbohydrates of tropical super sweet corn hybrids carrying the sh2 gene. All observed traits exhibited substantial interaction between hybrid and season, non-additive inherited, and low narrow-sense heritability. Long-term selections may contribute to the overwhelming dominance variance on all observed traits. Genotype TSC/H3-7-2 in the dry season was promising as a general combiner for high yield, plant stature, and early flowering. Genotype W54/Allure showed a favorable tester for kernel carbohydrates. Hybrid ws160 × W54/Allure was stable across different seasons for eating qualities. The other hybrid, TSC/H3-7-2 × W54/Allure, can be an alternative in the rainy season. The information obtained from this study can assist breeders in developing super sweet corn hybrids for better yield and eating quality.

Keywords: Sweet corn (Zea mays L.), combining ability, gene action, heritability, heterosis, hybrid breeding, sugar

Key findings: Long-term selections contribute to remarkable dominance variance on the maize (Zea mays L.) traits observed in this study. Agronomic traits and kernel carbohydrates of sh2-sweet corn are non-additive inherited and exhibit negligible narrow-sense heritability estimates. We propose two hybrids, ws160 × W54/Allure and TSC/H3-7-2 × W54/Allure, as promising tropical sh2-sweet corn hybrids.