Bioindicators selection to monitoring pyroxasulfone mobility and persistence in soil

Pyroxasulfone is a new herbicidal molecule with residual activity to be used in Brazilian agricultural areas, it is necessary to gather information about its behavior in the soil, as well as its persistence in the environment and the risk of environmental contamination. The objective of this work was to evaluate the sensitivity of species to pyroxasulfone in order to select potential plants to be used as bioindicators in herbicide soil activity experiments. Greenhouse experiments were conducted with four species as potential bioindicators including lettuce (Lactuca sativa), cucumber (Cucumis sativus), sorghum (Sorghum bicolor), and tomato (Solanum lycopersicum). The preemergence pyroxasulfone treatments at 0, 3.125, 6.25, 12.5, 25, 50, and 100 g a.i. ha-1. The percentage of injury of the treated species was evaluated by a visual scale of 0-100% at 7 and 14 days after treatment (DAT). We also evaluated the effect of the herbicide on plant height, root length, shoot fresh biomass, root fresh biomass, and total fresh biomass. Using the non-linear regression models, was possible to estimate the dose of pyroxasulfone required to obtain 50% of the response for the analyzed variable (I50). I50 values ​​were used to determine the susceptibility of the species evaluated. The pyroxasulfone dose-response experiments revealed three species with potential for bioassay studies. Overall, Lettuce was the most sensitive to herbicide. Sorghum may be useful species to detect pyroxasulfone soil activity based on plant height measurements (I50 = 9.7 g a.i. ha-1). Cucumber also showed to be a potential candidate as bioindicators. Tomato was considered tolerant of pyroxasulfone doses evaluated.