Traceability of glyphosate residues and its metabolite aminomethylphosphonic acid (AMPA) in glyphosate-resistant soybeans.

• Grant number: 24/16152-9
• Support Opportunities: Scholarships in Brazil - Master
• Start date: February 01, 2025
• End date: July 31, 2026
• Field of knowledge: Agronomical Sciences - Agronomy - Plant Health
• Principal Investigator: Kassio Ferreira Mendes
• Grantee: Laura Bordignon
• Host Institution: Centro de Energia Nuclear na Agricultura (CENA). Universidade de São Paulo (USP). Piracicaba , SP, Brazil

Abstract

Glyphosate is the most widely used herbicide on genetically modified Roundup Ready (RR)soybeans, which are resistant to the herbicide. These applications may lead to the presence ofglyphosate residues and its metabolite aminomethylphosphonic acid (AMPA) in RR soybeangrains treated with the herbicide. Therefore, studies on the traceability of glyphosate and AMPAresidues in RR soybean grains intended for human and animal consumption are essential.Additionally, the residues of these compounds in grains may be altered under water deficitconditions due to decreased absorption and translocation of the herbicide in the plant. Twoexperiments will be conducted in a growth chamber. The first experiment aims to understandthe relationship between the dose and number of herbicide applications with residual levels ofglyphosate and AMPA in grains and productive components of RR soybeans. Applications ofthree glyphosate doses (0.72; 2.16 e 4.32 kg a.e. ha-1) will be performed at three applicationtimings [30 days after planting (DAP) of the crop; 30/50 DAP; and 30/50/70 DAP], along witha control treatment with no herbicide application. The evaluations to be conducted include:plant height, number of true soybean leaves, grain yield, 100-seed weight, seed germinationtest, and glyphosate and AMPA residues in RR soybean grains by liquid chromatography withtandem mass spectrometry (LC-MS/MS). The second experiment seeks to analyze theabsorption and translocation of 14C-glyphosate in RR soybean plants after subjecting thesoybean plant to different levels of water stress. This experiment will be conducted under threeirrigation levels: no water deficit (constant irrigation), moderate water deficit (no irrigation for2 days before herbicide application), and severe water deficit (no irrigation for 5 days beforeapplication). Plant samples for absorption and translocation evaluations of 14C-glyphosate willbe collected at 3, 6, 12, 24, 48, and 72 hours after application (HAA) of the herbicide, with fourreplications. The absorption and translocation analysis will evaluate the amounts of absorbedproduct, unabsorbed product, and translocated product using liquid scintillation spectrometry(LSC), and image generation by RadioScanner. Thus, this study aims to promote the monitoringof glyphosate and AMPA residues in Brazilian RR soybean grains for domestic consumptionand export, leading to the rational use of glyphosate through more accurate recommendationsto producers, resulting in safer food.