Effects of climatic variations on the selectivity of S-metolachlor, fomesafen, and imazamox herbicides for common bean genotypes

The objective of this study was to assess the effect of crop seasons with contrasting climate conditions on the selectivity of fomesafen, imazamox, and S-metolachlor herbicides for common bean genotypes. Experiments were conducted under a split-plot arrangement with three replications, with herbicides (fomesafen, imazamox, S-metolachlor, and a control) in the plots and genotypes (IPR-Campos-Gerais, BRS-Perola, Caviano, BAF03, and BAF36) in the subplots; crop seasons (2022-2023 and 2023-2024) were considered a third factor. Phytotoxicity, chlorophyll content, plant height, number of leaves, stem diameter, root length, shoot weight dry, root basal angle, number of pods, number of beans per pod, bean dry weight, and bean yield were evaluated. Herbicide applications affected the growth and bean yield of genotypes, which varied between crop seasons. Plants were more affected when grown in the second crop season due to the El Niño effect, which causes large rainfall volumes and significantly increases temperatures in southern Brazil. This indicates that climatic variations, mainly water regime, were a determining factor for reductions in root and shoot growth, explaining the lower performance of genotypes in the second crop season. The commercial cultivars showed better performance than the two accessions. Climate variations affected the yield of common bean genotypes, which had higher performance in the first crop season. Key words: Phaseolus vulgaris, climate change, phytotoxicity, susceptibility, tolerance.