Resumo: Época de semeadura e ponto de corte de plantas de milho forrageiro são fatores importantes na produção de forragem de alto rendimento. O objetivo deste trabalho foi avaliar a participação dos componentes da planta em diferentes épocas de semeadura e estádios de colheita, em híbridos comerciais de milho recomendados para produção de forragem. O delineamento foi em blocos casualizados, com três repetições, esquema fatorial 4x2, sendo quatro híbridos de milho (P30B39H, DKB245, 2B688H e DKB330Y) e duas épocas de semeadura (outubro e novembro). O experimento foi conduzido no município de Guarapuava, PR. As avaliações foram realizadas nos estádios R4 e R5, sendo avaliados a porcentagem em matéria seca da folha (PPFOL), colmo (PPCOL), brácteas e sabugo (PPSAB), e grãos (PPGR) por meio de fracionamento da planta. O hibrido DKB245 apresentou menor participação de folhas, colmo, brácteas e sabugo, e maior participação de grãos nos estádios reprodutivos grãos farináceos e grãos farináceos duros, independente da época de semeadura. Com o avanço do estádio reprodutivo grãos farináceos para grãos farináceos duros houve elevação do percentual de grãos nos híbridos avaliados e redução na participação de folhas, colmos, brácteas e sabugo, nas duas épocas de semeadura (outubro e novembro). No estádio grãos farináceos duros os genótipos avaliados foram menos influenciados pelo efeito da época de semeadura, tendo maior participação de grãos para todos os genótipos, sendo a época indicada para a colheita da forragem. Palavras-chave:Forragem. Fragmentação da planta. Ponto de colheita. Zea mays L. Abstract:The sowing dates and harvesting times of forage maize are important factors in high-yield forage production. The objective of this study was to evaluate the participation of plant components for different sowing dates and harvest stages, in commercial maize hybrids recommended for the production of forage. The experimental design was of randomised blocks, three replications, in a 4 x 2 factorial scheme, being four maize hybrids (P30B39H, DKB245, 2B688H and DKB330Y) and two sowing dates (October and November). The experiment was carried out in Guarapuava, in the state of Paraná, Brazil (PR). Evaluations were done at stages R4 and R5, when the percentage of dry matter was evaluated by means of fractionation for the leaves (PPFOL), stem (PPCOL), grain (PPGR), and bracts and cob (PPSAB). The hybrid DKB245 displayed less participation of the leaves, stem, bracts and cob, and a higher participation of grain at the farinaceous and hard farinaceous grain reproductive stages, irrespective of sowing time. With the advancement of the farinaceous grain reproductive stage to hard farinaceous grain, there was an increase in the percentage of grain in the hybrids under evaluation and a reduction in the participation of the leaves, stem, bracts and cob for the two sowing dates (October and November). At the hard farinaceous grain stage, the genotypes under evaluation were less influenced by the effect of sowing time, there being a greater p...

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.

Questions about the faithful inheritance of the trait popping expansion (PE) in popcorn persist even eight decades after the first correlated study was initiated, raising doubts with regard to the best-suited breeding plans to obtain consistent genetic progress. The objective was to fill this scientific gap by implementing a genetic-statistical system based on analyses of segregating and non-segregating generations, for a more thorough examination of the partitioning of the genetic variance components in the expression of popping expansion in popcorn. Four crosses between popcorn (P) and dent corn (D) inbred lines were used [D29.109 x P9.4.6; D70H26.1 x P9.4.6; D60H23.1 x P9.4.6; D53H20.2 x P13] to establish the generations F1, F2, BC1 and BC2, which were evaluated together with the parents at two locations in the Northwest of Paraná, in randomized complete block design with three replications. The parents were chosen for their high divergence in PE to adequately establish generations. Additivity in PE expression was predominant in all crosses and at both locations. Intrapopulation breeding methods are the most suitable for selection gain in PE. Popping expansion can be used as an early predictor of promising inbred lines to obtain superior hybrids for popping expansion. Backcross methods are realistic and should be preferred in popcorn breeding. It is recommended to transfer the PE alleles from popcorn to common maize lines to combine vigor and high popping expansion.