Competitive ability of maize with weed species as a function of the inserted transgenic trait

ABSTRACT New technologies developed to control weeds in crops have flourished in recent years. Therefore, the objective of this work was to study the competitive ability of maize hybrids 2B433 (Enlist®), Pioneer 30F53 (VYHR®), and 13K288 PWE (Enlist®) and a conventional (non-transgenic) variety with a distinct biotechnological background when competing against wild poinsettia (Euphorbia heterophylla) and Alexandergrass (Urochloa plantaginea). Crops and competitors were studied in distinct plant proportions: 20:0, 15:5, 10:10, 5:15 and 0:20 plants per pot or 100:0, 75:25, 50:50, 25:75, and 0:100% (crop:weed) in replacement series experiments. Fifty days after emergence, the leaf area and aboveground dry mass were measured. Concomitantly, the photosynthetic and carboxylation efficiency and CO2 concentration were assessed in the leaf mesophyll. Maize hybrid 2B433 (Enlist®) showed better physiological and morphological performance compared to the conventional variety, and hybrids 13K288 PWE (Enlist®) and 30F53 (VYHR®) showed better performance when competing with wild poinsettia or Alexandergrass. The increased competitive ability seems to be due to the greater leaf area and aboveground dry mass reported for 2B433 (Enlist®). Therefore, the competitive ability presented by the hybrids was distinct, and we found no evidence that the transgenic event present in these hybrids affected their competitive ability. RESUMO Novas tecnologias desenvolvidas para controlar plantas daninhas nas lavouras surgiram nos últimos anos. Diante disso objetivou-se com o trabalho estudar a habilidade competitiva dos híbridos de milho 2B433 (Enlist®), Pioneer 30F53 (VYHR®), 13K288 PWE (Enlist®) e uma variedade convencional (não transgênica), com antecedentes biotecnológicos distintos, ao competir com leiteiro (Euphorbia heterophylla) e papuã (Urochloa plantaginea). O milho e os competidores foram estudados em diferentes proporções de plantas: 20:0; 15:5; 10:10; 5:15 e 0:20 plantas vaso-1 ou 100:0; 75:25; 50:50; 25:75 e 0:100% (cultura: planta daninha) em experimentos de série substitutiva. Aos 50 dias após a emergência das espécies foi determinado a eficiência fotossintética e de carboxilação, a concentração de CO2 no mesofilo foliar, além da área foliar e a massa seca da parte aérea das plantas. O milho híbrido 2B433 (Enlist®) apresentou melhor desempenho fisiológico e morfológico em relação à variedade convencional, e os híbridos 13K288 PWE (Enlist®) e 30F53 (VYHR®) quando em compet