TOLERÂNCIA DE LINHAGENS DE MILHO IRRIGADO AO HERBICIDA TEMBOTRIONE

Abstract

Corn lines have different behavior from commercial hybrids due to their high level of homozygosity, in relation to the effects caused by phytosanitary factors, which may make them more susceptible. Weed control in agriculture is essential to avoid competition and damage, and the lines can be very sensitive to herbicides used in maize crop. The active ingredient tembotrione is widely used in post-emergence in seed production fields. Therefore, this paper aimed to evaluate the tolerance of six irrigated corn lines to the tembotrione herbicide under the edaphoclimatic conditions of the Cerrado (Brazilian Savannah). The experiments were carried out under dry season, from May to September 2019, with conventional sprinkler irrigation, in the municipality of Goianésia, Goiás State (GO), Brazil. The experimental design was in randomized blocks, arranged in split plots with two factors; the first factor was corresponding to the six corn lines (Z9999L, ZKQMR3257L, 551CB, PGAG10051L, G55081L, and N34G34381L) and the second factor was corresponding to the doses of tembotrione herbicide (0, 120, 240, and 480 mL ha-1) with four replicates. Applications were carried out at the V3 phenological stage. The variables evaluated were: (a) grains per ear (GE); (b) finished product (FP); (c) productivity (kg. ha-1) (PROD); (d) photosynthesis (A); (e) stomatal conductance (gs); (f) evapotranspiration (E); (g) the potential quantum efficiency of photosystem II (Fv/Fm); and (h) the visual note of phytotoxicity (NF). Visual and physiological evaluations were carried out at seven, fourteen, and twenty-one days after herbicide application (DAA). It was found that there were no symptoms of toxicity (Visual Note) in the 43NG34381L genotype with the application of 480 mL ha-1, twice the recommended dose, being the most tolerant to the herbicide. The Z9999L, G55081L, and 551CB lines present low visual effects of toxicity, without any symptoms at fourteen and twenty-one DAA, although sensible to tembotrine at the recommended dose. The ZKQMR2357L and PGAG10051L lines were the most sensitive to the application of the tembotrione herbicide and showed symptoms of toxicity in all evaluations with the application of 240 mL ha-1 of the recommended dose in package. For Z9999L, ZKQMR2557L, and 43NG4381L lines, the downward trend was only significantly adjustable to linear regression for the Z9999L lineage, although there was a decrease in the production variables evaluated as the concentration of tembotrione increased.