Abstract Background This manuscript presents data of screening and dose-response curves of a goosegrass population from Primavera do Leste, MT, Brazil, which results in the first official report of multiple resistance of goosegrass to ACCase and EPSPs inhibiting herbicides in Brazil. Objective Evaluate the control of a goosegrass population from Primavera do Leste, MT, Brazil, suspected of resistance to the glyphosate, fenoxaprop-p-ethyl, and haloxyfop-methyl herbicides, using dose-response curves. Methods The study was carried out in two stages, the first in Brasília, DF, Brazil, and the second in Piracicaba, SP, Brazil. The first stage consisted in the initial evaluation and identification of resistance, which was confirmed in the second. In the first stage, the herbicides glyphosate, fenoxaprop-p-ethyl, and haloxyfop-methyl were applied to susceptible and resistant goosegrass populations (F1 and F2 generations) with plants with 2 and 3 tillers, using nine rates (0, 0.25, 0.5, 1, 2, 4, 8, 16, and 32 times the recommended rate). In the second stage, the herbicides were applied to susceptible and resistant populations with plants with 4 leaves, using 12 rates (0, 0.03125, 0.0625, 0.125, 0.25, 0.5, 1, 2, 4, 8, 16, and 32 times the recommended rate). Results The high sensitivity of susceptible plants combined with the high resistance level of resistant ones resulted in high resistance factors for fenoxaprop-p-ethyl and haloxyfop-methyl, with values greater than 27.8. The resistance factor for glyphosate ranged from 3.3 to 11, depending on growth stage at application time. Conclusions The goosegrass population from Primavera do Leste, MT, Brazil, presented resistance to EPSPs (glyphosate) and ACCase (haloxyfop-methyl and fenoxaprop-ethyl) inhibiting herbicides.

RESUMO Produtividades elevadas de milho em sistemas com alta tecnologia estão relacionadas à correta implantação da lavoura. Neste trabalho objetivou-se avaliar os efeitos da variabilidade na distribuição de sementes de milho na linha de semeadura sobre os componentes de produção do milho. A pesquisa foi realizada em condições de Cerrado, no município de Urutaí, GO. O delineamento experimental utilizado foi de blocos casualizados em esquema fatorial 5 x 2, com quatro repetições. Avaliaram-se os efeitos de cinco coeficientes de variação (0, 20, 40, 60 e 80%) de desuniformidade na distribuição espacial de sementes na linha de semeadura em dois híbridos de milho (P30F53HX e P3646HX). Não foram observadas interações para as variáveis analisadas no milho; contudo, foram diminuídos, com o aumento da desuniformidade na distribuição das sementes na linha, o diâmetro do colmo, a massa de cem grãos, o número de fileiras por espiga, o número de grãos por fileiras e o comprimento da espiga. Também foram observadas reduções lineares no rendimento de grãos de milho com o aumento do coeficiente de variação na distribuição espacial das sementes na linha de semeadura. Entre os híbridos o 30F53HX apresentou maior massa de cem grãos.

ABSTRACT High corn yields in high-tech systems are related to proper crop implementation. This study aimed to evaluate the effects of variability in the distribution of seeds along the planting row on corn production components. The study was conducted under Cerrado conditions in the municipality of Urutaí, GO, Brazil. The experimental design was randomized blocks in a 5 x 2 factorial scheme, with four replicates. The effects of five coefficients of variation (0, 20, 40, 60 and 80%) of non-uniformity in the spatial distribution of seeds along the planting row of two corn hybrids (P30F53HX and P3646HX) were evaluated. No interactions were observed for the analysed corn variables. However, as the non-uniformity in seed distribution along the planting row increased, stalk diameter, hundred-grain weight, number of rows per ear, number of kernels per row and ear length decreased. Additionally, linear reductions were observed in corn grain yield with the increase in the coefficient of variation of the spatial distribution of seeds along the planting row. Between the hybrids, the 30F53HX showed higher hundred-grain weight.