STUDY OF THE EFFECT OF Azospirillum brasilense Az39 ON THE RESIDUALITY OF GLYPHOSATE USED IN CORN CROPS

PAULA CARDOZO; CARLOS SOSA; MATÍAS CARDENA; CLAUDIA TRAVAGLIA; FABIANA D´ERAMOS; MARCELA MORESSI

Congreso; 8º Congreso Latinoamericano de Residuos de Plaguicidas; 2021

Currently, there is an increasing need to expand to the maximum the knowledge of thephysical-chemical characteristics, the form of action and the environmental impact ofherbicides, in order to make a rational use of them1. In the development of a herbicide,aspects such as its chemical formula, its behavior within the plant to the impact on theenvironment should be studied, in order to offer the farmer effective and safe tools. Thus,studies related to forms of degradation of herbicides that remain as residues are importantto achieve a minimum environmental impact1.The time that a herbicide remains active in the soil, after it produced its effect, is calledpersistence. Any factor that alters the disappearance or decomposition of herbicidesaffects their persistence. Nowadays, different strategies are being developed to eliminatethese substances in an economic and ecological way. Numerous studies have shownthat soils contaminated with pesticides can be decontaminated by the action of specificmicroorganisms2.In this work, an in vitro assay was carried out on the interaction between the RhizobacteriaAzospirillum brasilense Az39 and glyphosate in order to determine if the microorganismwas capable of reducing the accumulation of glyphosate?s residues.For the study, a bacterial inoculum was prepared using the Azospirillum brasilense Az39strain, grown in LB medium. From it, in vitro survival tests of the bacterial culture againstglyphosate were performed, as well as its ability to use it as a carbon source. In the firstcase, a selective medium for nitrogen-fixing bacteria was used: NFb (nitrogen free broth),to which glyphosate sources were added. While for the second case, the same culturemedium was prepared but without the addition of the carbon source, which was replacedby glyphosate. The concentration of glyphosate and AMPA was determined in thesetreatments where the culture medium conserved all the nutritional sources for the growthof A. brasilense Az39, representing the availability of nutrients that the bacteria usuallyhave. Their quantification was carried out using HPLC Chromatography with MS / MSdetection after derivatization with FMOC3.The obtained results showed a 30% decrease in the glyphosate concentration in theculture medium inoculated with A. brasilense compared to the treatment without bacterialinoculation. The treatment in which the Az39 culture was inactivated did not showsignificant differences with respect to the treatment without Az39. In the control treatment(-), neither glyphosate nor AMPA was detected. The ability of Azospirillum brasilenseAz39 to use glyphosate as a carbon source was demostrated, even in the presence of allits nutritional sources, which is promising for its degradation in the floor.