Relationships between genetic distance, combining ability, and agronomic performance of tropical maize single-cross hybrids under different plant population

With the purpose on improving the selection of maize hybrids under contrasting plants population, this study evaluated the association between genetic distance, general and specific combining abilities (GCA and SCA), and adjusted means of tropical maize single-cross hybrids under two plant populations. Twenty-two inbred lines were genotyped with a 25k SNP marker chip, crossed in a partial diallel (11 x 11), and evaluated under traditional (60,000 plants ha^-1) and high (100,000 plants ha^-1) plants population, in an incomplete block design with two replications, considering 21 agronomic traits. Diallel analyses followed the Comstock and Robinson (1948) model, and Pearson correlation coefficients were estimated among adjusted means, GCA and SCA effects, and GD estimated from SNPs markers. Correlations between adjusted means and SCA were significant for most traits, with the highest magnitude for DTP, GY, and NKE. Genetic distance showed a negative correlation with DTP and DTS and a positive one with GY, indicating that more divergent parents tend to generate more productive and early-maturing hybrids. The similarity of the combining ability correlation networks under both plant populations indicates that evaluating maize inbred lines under different plant populations is unnecessary. However, genetic distance, being moderately correlated, is a limited isolated predictor.