Objective To improve the breeding efficiency of sweet-waxy maize by accurately evaluating parental combining ability and efficiently utilizing heterosis.

Method Five waxy maize inbred lines were used as female parents, and five double-recessive sweet-waxy inbred lines were used as male parents. Twenty-five hybrid combinations were constructed using the NCⅡ mating design. The general combining ability (GCA) and specific combining ability (SCA) of agronomic traits were systematically analyzed, and excellent parents and hybrid combinations were screened based on heritability analysis.

Result The inbred lines HNM05 (GCA for plant height = 26.45), and YN170 (GCA for ear row number = 0.96) exhibited significant positive GCA effects for key traits and could be utilized as core parents. Hybrid combinations HNM05/YN170 (SCA for plant height = 18.56) and 15YN02-1/YN169 (SCA for ear weight = 28.83) demonstrated significant heterosis, indicating high yield potential. Heritability analysis revealed that traits such as ear length (h²_N=66%) and plant height (h²_N=59%) had high genetic stability, making them suitable for early-generation selection. In contrast, traits such as single ear weight (h²_N=19%) and kernel number per row (h²_N=25%) were significantly influenced by environmental factors, requiring advanced-generation screening. The hybrid combination HNM05/YN167, screened in this study and named 'Gantiannuo No. 3', has been approved at the provincial level. This validates the practical value of combining ability analysis.

Conclusion Combining ability and heritability varied significantly among different traits of sweet-waxy maize. Parental screening should consider both GCA and SCA. Traits with high heritability, such as ear length and plant height, are suitable for early-generation selection, while traits with low heritability, such as single ear weight and kernel number per row, require advanced-generation selection.