Resumo -O objetivo deste trabalho foi identificar o tipo de ação gênica predominante para resistência a Exserohilum turcicum, Phaeosphaeria maydis, Physopella zeae e Puccinia polysora, e determinar o potencial genético de linhagens endogâmicas de milho (Zea mays) para a obtenção de híbridos com elevado desempenho agronômico e resistência a doenças foliares. Os 41 híbridos F 1 , provenientes de cruzamentos dialélicos entre dez linhagens endogâmicas, e as testemunhas P3069, P30F90, BG7060, Balu761 e Dow2A120 foram avaliados em quatro locais, tendo-se utilizado o delineamento experimental de blocos ao acaso, com três repetições. Os híbridos LGS 3 xLGS 9 , LGS 2 xLGS 6 , LGS 2 xLGS 4 e LGS 2 xLGS 3 apresentaram excelente desempenho em comparação às testemunhas, quanto aos diferentes caracteres avaliados. As linhagens com maior frequência de alelos favoráveis foram LGS 2 , LGS 9 , LGS 4 e LGS 3 . Os efeitos gênicos aditivos são os mais importantes para a resistência a P. maydis e altura de espiga, enquanto os não aditivos são mais importantes para a produtividade, altura de planta, resistência à E. turcicum, P. zeae e P. polysora.Termos para indexação: Exserohilum turcicum, Phaeosphaeria maydis, Physopella zeae, Puccinia polysora, Zea mays, efeito genético. Diallel analysis of maize inbred lines with emphasis on resistance to leaf diseasesAbstract -The objective of this work was to identify the predominant type of gene action for resistance to Exserohilum turcicum, Phaeosphaeria maydis, Physopella zeae and Puccinia polysora, and to determine the genetic potential of maize (Zea mays) inbred lines in order to obtain hybrids with high agronomic performance and resistance to leaf diseases. Forty-one F 1 hybrids from the diallel crosses between ten endogamic lines, and the controls P3069, P30F90, BG7060, Balu761, and Dow2A120 were evaluated in four places, using a randomized block experimental design, with three replicates. The hybrids LGS 3 xLGS 9 , LGS 2 xLGS 6 , LGS 2 xLGS 4 and LGS 2 xLGS 3 showed an excellent performance in comparison with the controls, for the different characters evaluated. The lines with higher frequency of favorable alleles were LGS 2 , LGS 9 , LGS 4 and LGS 3 . The additive genetic effects are the most important for the resistance to P. maydis and for ear height, while nonadditive genetic effects are more important for yield, plant height, resistance to E. turcicum, P. zeae and P. polysora.

The objective of this study was to evaluate the combining ability and inbreeding depression of commercial maize hybrids for agricultural traits. Twenty-two commercial maize hybrids, 96 F 1 crosses from a partial diallel scheme, 22 S 1 populations and 4 controls were evaluated in a 12x12 simples square lattice experimental setup, totaling 144 treatments, in the municipality of Sabáudia (PR), Brazil, for harvests from 2011/2012 and 2012/2013. Three traits were evaluated: grain yield, plant height and ear height. The Griffing method (1956) was applied for the evaluation of the general combining ability (GCA) and specific combining ability (SCA). The 30B39, 30K64 and 30B30 hybrids showed increased yield, 30F53 and P1630 showed reduced plant height and AG9040 and AG7010 showed reduced ear height. These hybrids can be recommended for the extraction of inbred lines and formation of composites followed by intrapopulation selection. The combinations 30B39 x AG8088, 30B39 x AG9045 and P1630 x AG8021 showed desirable SCA effects for grain yield, plant height and ear height and are recommended for use in reciprocal recurrent selection programs. High magnitudes of inbreeding depression were verified for yield and lower values for inbreeding depression for plant and ear heights. Thus, strategies are recommended for interpopulation breeding accompanied by inbred lines extraction.

The objective of this study was to evaluate the combining ability and inbreeding depression of commercial maize hybrids for agricultural traits. Twenty-two commercial maize hybrids, 96 F 1 crosses from a partial diallel scheme, 22 S 1 populations and 4 controls were evaluated in a 12x12 simples square lattice experimental setup, totaling 144 treatments, in the municipality of Sabáudia (PR), Brazil, for harvests from 2011/2012 and 2012/2013. Three traits were evaluated: grain yield, plant height and ear height. The Griffing method (1956) was applied for the evaluation of the general combining ability (GCA) and specific combining ability (SCA). The 30B39, 30K64 and 30B30 hybrids showed increased yield, 30F53 and P1630 showed reduced plant height and AG9040 and AG7010 showed reduced ear height. These hybrids can be recommended for the extraction of inbred lines and formation of composites followed by intrapopulation selection. The combinations 30B39 x AG8088, 30B39 x AG9045 and P1630 x AG8021 showed desirable SCA effects for grain yield, plant height and ear height and are recommended for use in reciprocal recurrent selection programs. High magnitudes of inbreeding depression were verified for yield and lower values for inbreeding depression for plant and ear heights. Thus, strategies are recommended for interpopulation breeding accompanied by inbred lines extraction.

The purpose of this study was to evaluate the discriminatory capacity of tester lines for tropical corn lines converted to supersweet shrunken (sh2) gene, for the development of hybrids adapted to tropical conditions. Lines were used as female parents in crosses with three testers: open-pollinated mixed variety; supersweet line L4; supersweet commercial hybrid Tropical Plus. Four trials were carried out to evaluate topcrosses in Maringá - PR e Sabáudia - PR, Brazil in the main growing season of 2015/16. The following traits were evaluated: total ear weight (TEW, in kg), commercial ear weight (CEW, in kg) and total soluble solids (TSS, in °Brix). The GCA estimates for TEW and CEW were highest for L4. The lines Balu-114 and UEM-25 were selected based on the effects of g ̂ ifor the traits studied and should be used in the establishment of base populations for the breeding of superior lines. The s ̂ ijvalue for TEW was highest for cross BALU-182 x Tropical, while for CEW was the highest value for cross BALU-94 x Mista.