Polymorphism, population structure, and multivariate relationships among secondary traits in open-pollinated corn heterotic groups

Plant, ear and kernel traits directly or indirectly associated with grain yield in corn (Zea mays L.) have been suggested as “secondary” traits to select for larger grain yield, especially in open-pollinated corn varieties and their hybrids. Polymorphism, population structure, and multivariate relationships among 34 secondary traits and their impact on grain yield were quantified in 46 open-pollinated varietal hybrids within eight maternal heterotic groups. Large levels of polymorphism and population differentiation especially for reproductive traits, and above-average values for diversity indices, frequency of desirable trait variants, and population differentiation were found for almost all secondary traits. Maternal heterotic groups were identified as potential sources of desirable variants of single or multiple traits appropriate for adaptation to short-growing seasons, low-input farming and adverse environmental condition.