ABSTRACT The objectives were to estimate the potential of S2 corn progenies for forage-related traits, and use of AMMI analysis to evaluate topcrosses compared to the classic analyzes. Progenies were crosses with four different testers: LG 6030, 2B688, 9.H3.33 and 53F.P37. Topcross hybrids were evaluated in four 9 x 9 simple square lattice design, during the 2017/18 season at Maringa, Parana State. Grain yield, forage fresh matter yield, and forage dry matter yield were measured. Classical approach was composed by variance components, general and specific combining ability, whereas AMMI analysis was performed for progenies x testers interaction, considering additive main effects and multiplicative effects. Considering the classical approach, testers LG 6030 and 2B688 better expressed the genetic variability between progenies for grain yield. AMMI analysis allowed the partitioning of the sum of squares in additive main effects and multiplicative effects, being a complementary result for the classical approach. Progeny 14 was selected due to higher general combining ability for grain yield, forage fresh matter and forage dry matter yield. Topcrosses 14x9.H3.33 and 14x2B688 were selected due to their higher specific combining ability, additive and multiplicative effects. The AMMI analysis was effective and helped in the interpretation of the results.

ABSTRACT. In this study, we aimed to estimate general and specific combining abilities (GCA and SCA, respectively) and to verify genetic divergence (Rogers distance, Unweighted Pair-Group Method Using Arithmetic Average - UPGMA) using microsatellite markers in maize inbred lines. Using a partial diallel scheme, a total of 19 inbred lines were crossed as (9 x 10), which were derived from the single hybrids SG6015 and P30F53, respectively. The 90 hybrids were evaluated in an incomplete randomized block design with common checks and three replications during the 2017-2018 growing season. Flowering time, average plant height, ear height insertion, average ear diameter, ear length, number of lodged and broken plants, mass of 100 grains and grain yield were measured. According to the analysis of variance, GCA, and SCA were significant (p < 0.05) in all the measured traits; inbred line B as well as 1 and 8, derived from the single hybrids SG6015 and P30F53, respectively, were selected due to their higher GCA values in grain yield to be used in crosses as testers, while the single cross hybrid (B x 1) was selected due to their higher SCA value in grain yield to be used in future breeding programs. The molecular marker analysis divided the inbred lines into two groups, where the highest dissimilarity (0.74) was observed between lines A and 9; however, these did not result in a high SCA value, therefore the hybrids obtained by such crossings were not selected for grain yield.

ABSTRACT. 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.