Tolerância da bactéria diazotrófica Gluconacetobacter diazotrophicus a herbicidas utilizados na cultura da cana-de- açúcar

Abstract

The objective of this work was to identify herbicides used in the sugarcane crop that affects neither the growth of nor the process of biological nitrogen fixation (BNF) by the diazotrophic bacterium Gluconacetobacter diazotrophicus. Eighteen herbicides (paraquat, ametryne, amicarbazone, diuron, metribuzin, [hexazinone + diuron], [hexazinone + clomazone], clomazone, isoxaflutole, sulfentrazone, oxyfluorfen, imazapic, imazapyr, [trifloxysulfuron sodium + ametryne], s-metolachlor, glyphosate, MSMA e 2.4-D) were tested in their respective commercial doses. For this, we determined the duration of lag phase, generation time and maximum cell density of G. diazotrophicus. We also evaluated the impact of herbicides on nitrogenase activity of G. diazotrophicus measured by the technique of acetylene reduction assay. Diuron, metribuzin, 2.4-D and MSMA caused a small reduction in maximum growth of G. diazotrophicus in vitro. Amicarbazone, [hexazinone + clomazone] and clomazone showed some bacteriostatic effect on G. diazotrophicus. Treatments containing the herbicide paraquat and glyphosate resulted inhibitory effect on BFN by G. diazotrophicus.