Knowledge about relationships between traits can contribute to raising the efficiency of selection of superior genotypes. The objective of this study was to estimate the correlations, direct and indirect effects of agronomic, chemical and physical traits of kernels on popping expansion (PE) in popcorn (Zea mays L.). The trial was carried out in the 2017/2018 growing season, in Maringá -PR, with 49 treatments, which consisted of 43 popcorn, four flint, and two sweet corn. The trial was arranged in a randomized complete block design with three replications. Multiple agronomic, chemical, physical, and popcorn quality traits were evaluated. Analysis of variance was performed to estimate the coefficients of phenotypic and genotypic correlations and the direct and indirect effects of path analysis. The genotypes were partitioned into genotype within each kernel type (popcorn, flint, and sweet corn) and two more contrasts (popcorn vs. [flint + sweet corn]) and flint vs. sweet corn. Positive phenotypic (.76) and genotypic correlations (.81) between popping expansion and pericarp thickness were detected. Kernel length had negative phenotypic (−.75) and genotypic correlations (−.78) with PE. Path analysis indicated that pericarp thickness has a direct and positive effect on PE and that the observed positive correlation with thermal diffusivity of the kernel pericarp and kernel length can be explained by indirect effects of the pericarp thickness. Evaluating kernel length may be most prudent considering economical and practical constraints to popcorn breeding programs.

Our objectives were to evaluate general and specific combining ability (SCA) and genetic divergence among tropical maize inbred lines using single sequence repeat (SSR) markers. Thirteen inbred lines were crossed based on a complete diallel scheme. Hybrids and three checks were evaluated in a lattice experimental design. Silk and anthesis flowering, average plant height, average ear height, white spot (Pantoea ananatis) and gray leaf spot (Cercospora zeae-maydis) severity, and grain yield were evaluated. Significant differences (p < 0.05) for general and specific combining abilities were observed for all traits. Based on additive effects, inbred lines 1 (Flash) and 12 (SG 6015) were selected to reduce the flowering period and plant and ear height. Inbred lines 2 (CD 303) and 3 (AG 8080) were selected to reduce disease severity. For the simultaneous increase in grain yield and reduced severity of diseases, line 11 (AG 9090) as a parent or tester in topcross schemes is recommended. According to non-additive effects, crosses 2 (CD 303) × 13 (DKB 747) and 11 (AG 9090) × 12 (SG 6015) were selected for grain yield and future breeding programs. Six groups were identified using SSR markers; a major group contained six inbred lines. Because of the minor relationship between genetic divergence and SCA effects on grain yield limits, the use of the groups for future divergent crosses is recommended.