The objective of this work was to identify corn (Zea mays) genotypes with forage potential and to evaluate the efficiency of testers to discriminate forage traits in topcrosses, considering the contribution of additive and nonadditive genes. The experiment was carried out in the 2015/2016 and 2016/2017 crop seasons, in a randomized complete block design with three replicates. Thirty S3 corn progenies were evaluated in topcrosses with the AG8025, P30B39, MLP102, 60.H23.1, and 70.H26.1 testers. The following traits were assessed: forage dry mass yield, neutral detergent fiber, acid detergent fiber, and forage dry mass degradability. Progenies 205.2, 159.6, and 199.2, in this order, presented the best performance for forage potential. Testers 60.H23.1 and 70.H26.1 better expressed the genetic variability between progenies. For all traits in both crop seasons, there is a predominance of the action of genes of nonadditive effects.

Super sweet is classified as a special type of corn, due to the presence of genes which promote sugar accumulation in grains, significantly reducing starch content in the endosperm. This study aimed to evaluate the agronomic performance of experimental super sweet corn hybrids, carrying the gene shrunken-2, in order to identify and select promising genotypes for Southern Brazil. The experiments were carried out in two sowing seasons in 2017/18, in the experimental field of UNICENTRO, Guarapuava-PR, Brazil. Thirty-two experimental hybrids resulting from an 8x4 partial diallel among super sweet corn inbred lines from four distinct populations were evaluated along with two commercial hybrids (BRS Vivi and Tropical Plus) used as checks. Traits of agronomic and commercial interest were evaluated: male flowering (MF), husk covering index (HCI), yield of husked ears (YHE), grain yield (GY), commercial prolificacy (CPR), percentage of commercial ears (PCE), color (COL) and soluble solids (SS) of the grains. We verified significant differences among the experimental hybrids, except for COL. There was no significant effect of sowing season regarding to SS. Genotypes x seasons interaction was significant for YHE, GY, CPR, PCE and COL. There are promising experimental hybrids showing performances superior to commercial super sweet corn hybrids used in Brazil. The experimental hybrids D2-61 x D5-41 and D3-10 x D5-43 were superior to the other experimental genotypes. The experimental hybrid D2-61 x D5-41 shows potential to meet the demands of the current super sweet corn market.

RESUMO – A utilização de híbridos comerciais é uma opção para gerar populações-base para obter novas linhagens superiores. Portanto, objetivou-se com a pesquisa selecionar linhagens S3 superiores para produtividade de grãos, avaliadas em dois espaçamentos, para ser avançadas no processo de endogamia. Para isso, foram avaliados 75 híbridos topcrosses juntamente com seis híbridos comerciais (DKB245 PRO2, P30F53 H, P30B39 H, AS1572, DKB315 PRO e SG6030 PRO). Foi utilizado o delineamento látice triplo 9x9 para avaliação de florescimento masculino (FM), altura de planta (AP), altura de espiga (AE), prolificidade (PR) e produtividade de grãos (PG). Houve diferença significativa entre genótipos para todas as características avaliadas, interação genótipo x espaçamento para a PG e AE. Não foi constatada diferença significativa para espaçamento entre linhas. Os híbridos topcrosses TC102-05, TC102-06, TC102-15, TC102-16, TC102-17, TC102-21 e TC102-24 se destacaram nos dois espaçamentos entre linhas, aliando características de produtividade de grãos, estatura e ciclo precoce, cujas respectivas linhagens deverão ser avançadas no processo de endogamia.Palavras-chave: Zea mays L., testador, linhagens parcialmente endogâmicas. EVALUATION OF S3 MAIZE LINES TOPCROSSED IN TWO ROW SPACINGS ABSTRACT – The use of commercial hybrids is an option to generate base populations for obtaining new superior lines. The objective of this study was to select S3 lines superior for grain yield, evaluated in two row spacings, to be advanced in the process of inbreeding. For this, 75 topcross hybrids were evaluated along with six commercial hybrids (DKB245 PRO2, P30F53 H, P30B39 H, AS1572, DKB315 PRO and SG6030 PRO). The 9x9 triple lattice design was used.to evaluate the agronomic traits of male flowering (MF), plant height (PH), ear heigth (EH), prolificacy (PR) and grain yield (GY). There was a significant difference between genotype for all traits evaluated, interaction genotype x spacing for EH and GY. No significant difference was observed for line spacing. The topcross hybrids TC102- 05, TC102-06, TC102-15, TC102-16, TC102-17, TC102-21 and TC102-24 were superior in the two row spacings, combining the characters of grain yield, stature and early cycle, whose lines should be advanced in the process of endogamy.Keywords: Zea mays L., tester, partially inbred lines.

Maize forage is commonly used as silage in milk and beef cattle livestock production systems. Despite the wide variety of maize hybrids with high potential for grain production, few available hybrids have been developed exclusively for forage aptitude. The present study aimed to select S3 maize progenies derived from the single hybrid AS1572 based on the combining ability of forage traits in topcrosses with testers AG8025, 70.H26.1, and MLP102. The 135 resulting topcross hybrids were assessed in partial diallel in Guarapuava and Rio Bonito do Iguaçu, Paraná State, Brazil. Were evaluated the contents of neutral detergent fiber (NDF, %DM) and acid detergent fiber (ADF, %DM), forage dry matter yield (DMY, t ha-1), and in situ digestibility of forage dry matter (DIG, %DM). For all evaluated traits, the variability allowed us to select superior progenies. Progenies 3.1, 22.1, and 39.1stood out in terms of NDF, ADF, and DIG, whereas progenies 47.1, 73.1, 79.1, and 90.2 were efficient in increasing the forage dry matter yield. The testers AG8025 and 70.H26.1, of narrow genetic base, are the best to explore genetic variability among progenies.

Resistance of maize inbred lines to major leaf diseases should be characterized for the development of new hybrids in breeding programs. Thus, this study aimed to assess the severity of leaf diseases in maize inbredlines with different kernel hardnessand two sowingseasons. We assessed four inbred lines and one check hybrid with dent kernels and four inbred lines and a check hybrid with flint kernels. Treatments were conducted in two sowing seasons, one in October, and another in December 2013. The symptoms of gray leaf spot (Cercospora zeae-maydis), northern leaf blight (Exserohilum turcicum), and white leaf spot (a complex of Phaeosphaeria maydis and Pantoea ananatis) were assessed every 10 days from flowering. The area under the disease progress curve was also calculated. Severity level of the diseases was higher in inbred lines when compared to the check hybrds (AG8041 PRO and P30R50YH), regardless of kernel hardness. Dent-kernel inbred lines showed a higher severity of northern leaf blight symptoms when compared to flint-kernelones. It is worth mentioning that disease severity increased as sowing was delayed. Keywords: Cercospora zeae-maydis. Exserohilum turcicum. Pantoea ananatis. Phaeosphaeria maydis. Zea mays. ResumoA caracterização de linhagens de milho quanto à resistência às principais doenças é fundamental para o desenvolvimento de novos híbridos em programas de melhoramento. Assim, o objetivo deste trabalho foi avaliar a severidade de doenças foliares em linhagens de milho com diferentes texturas de grãos em duas épocas de semeadura. Foram avaliadas quatro linhagens e um híbrido testemunha com grãos dentados e quatro linhagens e um híbrido testemunha com grãos duros. Os tratamentos foram conduzidos em duas épocas de semeadura, em outubro e em dezembro de 2013. A partir do florescimento, a cada 10 dias, foram avaliadas as doenças foliares cercosporiose (Cercospora zeae-maydis), helmintosporiose (Exserohilum turcicum) e mancha branca (complexo Phaeosphaeria maydis/Pantoea ananatis). Foi calculada a área abaixo da curva do progresso das doenças (AACPD foi maior nas linhagens, comparativamente aos híbridos testemunhas AG8041 PRO e P30R50YH, independentemente da textura dos grãos. As linhagens de textura dentada apresentaram maior severidade de sintomas da helmintosporiose, quando comparada às linhagens de grãos duros. Houve aumento da severidade das doenças avaliadas com o atraso da semeadura.