Impactos ecotoxicológicos de herbicidas à base de diquat e em combinação com flumioxazina: uma análise comparativa através de bioensaios com modelos vegetais

Abstract

Pesticides are a class of organic compounds used to control the growth, obstruction, or death of different organisms that cause damage to crops. However, several studies have reported multiple environmental harms associated with these substances. Herbicides are a type of pesticide used to control undesired plants and are divided into different classes. In this context, ecotoxicology emerges as a science aimed at studying the effects of contaminants and pollutants on living organisms and ecosystems. Frequently, herbicide active ingredients are reformulated to achieve better performance at lower doses. In this sense, the herbicide Burner was introduced to the agricultural market in 2022, promoted as “environmentally friendlier” due to requiring a smaller amount of product, being composed of a diquat salt and flumioxazin. This study aimed to evaluate the toxicity of the herbicide Spraykill, based on diquat and belonging to the bipyridylium class, and the herbicide Burner, based on diquat and flumioxazin, through cytogenotoxicity, germination, and seedling development bioassays, following ISO 18763 (2016) guidelines with some modifications. For the germination and development assays, the plant models Lactuca sativa L. (lettuce), Cenchrus americanus (L.) Morrone (pearl millet), Raphanus sativus L. (radish), and Triticum aestivum L. (wheat) were used. Cytogenotoxicity bioassays were performed with the model Allium cepa (L.). For the germination and development assays, ten solutions of each herbicide were prepared, with diquat concentrations ranging from 10.0 to 2000.0 mg/L in Spraykill® and from 0.4 to 85.0 mg/L in Burner®, plus a negative control containing only distilled water. For cytotoxicity assays, diquat concentrations ranged from 0.6 to 6.6 mg/L for Spraykill® and from 0.1 to 1.8 mg/L for Burner®. In the growth and development tests, the following parameters were evaluated: germination percentage, germination speed index, fresh mass, root length, and shoot length of seedlings. In the cytotoxicity assays, the mitotic index and the presence of nuclear and chromosomal aberrations were analyzed. Data analysis was performed using R software, applying ANOVA and Tukey’s test, with a significance level of p < 0.05. The results showed significant toxic effects on non-target species across all evaluated parameters, with Lactuca sativa standing out as the most sensitive species compared to the others. In the cytogenetic analysis, both herbicides significantly reduced the mitotic index, with Spraykill® being particularly noteworthy for exhibiting cytotoxic effects at concentrations approximately 157 times lower than those recommended for commercial use. Chromosomal and nuclear aberrations such as bridges, micronuclei, and buds were observed, especially in treatments with higher concentrations. EC50 values reinforced the higher toxicity of Burner®, whose effective concentrations were consistently lower than those observed for Spraykill®. Overall, the results demonstrate that both herbicides present cytotoxic and genotoxic potential, posing relevant environmental risks even at concentrations below those recommended for application.