Optimization of the glomalin-related soil protein extraction and quantification method, extracted from systems with soybean predominance

COMMATTEO JAQCUELINE GISELLE; BARBIERI, PABLO ANDRÉS; COVACEVICH, FERNANDA

Virtual

Congreso; XXX Reunión Latinoamericana de Rizobiología y V Congreso Latinoamericano sobre Microorganismos Promotores del Crecimiento Vegetal; 2021

Glomalin is a soil particle binding glycoprotein and has been postulated as an indicator of arbuscular mycorrhizal fungi (AMF) activity, which could plays a key role in soil stability. The term glomalin-related soil protein (GRSP) is used to describe the different fractions extracted in soil. Total GRSP (T-GRSP) corresponds to the protein fraction strongly bounds to soil particles and is obtained after several extractions. The objective of this study was to optimize the GRSP extraction and quantification method and to determine the effect of agricultural management of the parameter. For this analysis, soil (Typic Argiudoll) samples were collected from three longterm field experiments at three sites of the Argentinean Humid Pampas: Balcarce, Marcos Juárez and General Villegas (sites 1, 2 and 3 respectively), on 2017/18 growing season, in two sampling seasons (autumn and winter). Samples were extracted from: 1) soybean monoculture (Sb); 2) cover crop/soybean (CC/Sb); and 3) soybean in rotation with Maize and Wheat (CC/Sbrot). Our protocol (called Optimized Method, OpM) was customized by adding modifications to the Standard Method (SM). We used tubes of 10 mL instead of 50 mL (where solution losses could be higher) and centrifuge equipment is more efficiently used. T-GRSP concentration was obtained by the sum of absorbance (A595) determined after each GRSP-extraction cycle, instead of quantifying the T-GRSP in the total volume of the supernatant, composed by a mixture of each extraction cycle supernatants. Finally, the extraction process was stopped when the GRSPquantification approached zero. The OpM revealed more differences among treatments than SM. Highest T-GRSP concentrations were recorded at site 1 in which highest T-GRSP contents were obtained with both methods in management systems other than Sb. At sites 2 and 3, differences among treatments were only found when using the OpM, and highest concentrations were recorded at the alternative cropping systems (CC/S and/or CC/Sb-rot). As expected, a strong correlation was observed between the first cycle of extraction of the T-GRSP (1stECGRSP) and T-GRSP. We highlight that OpM contributes both to optimization in the extractionquantification precision and in the reduction of the process time. The OpM allowed to detect effect of management practices towards sustainable management of GRSP concentration