Crop inoculation with Glomus cubense isolate (INCAM-4, DAOM-241198) promotes yield in banana, cassava, forages, and others. Yield improvements range from 20 to 80% depending on crops, nutrient supply, and edaphoclimatic conditions. However, it is difficult to connect yield effects with G. cubense abundance in roots due to the lack of an adequate methodology to trace this taxon in the field. It is necessary to establish an accurate evaluation framework of its contribution to root colonization separated from native arbuscular mycorrhizal fungi (AMF). A taxon-discriminating primer set was designed based on the ITS nrDNA marker and two molecular approaches were optimized and validated (endpoint PCR and quantitative real-time PCR) to trace and quantify the G. cubense isolate in root and soil samples under greenhouse and environmental conditions. The detection limit and specificity assays were performed by both approaches. Different 18 AMF taxa were used for endpoint PCR specificity assay, showing that primers specifically amplified the INCAM-4 isolate yielding a 370 bp-PCR product. In the greenhouse, Urochloa brizantha plants inoculated with three isolates (Rhizophagus irregularis, R. clarus, and G. cubense) and environmental root and soil samples were successfully traced and quantified by qPCR. The AMF root colonization reached 41-70% and the spore number 4-128 per g of soil. This study demonstrates for the first time the feasibility to trace and quantify the G. cubense isolate using a taxon-discriminating ITS marker in roots and soils. The validated approaches reveal their potential to be used for the quality control of other mycorrhizal inoculants and their relative quantification in agroecosystems.

Agroécologie AgroSup Dijon CNRS Université Bourgogne INRAE Université Bourgogne Franche Comté 21000 Dijon France

Arbuscular Mycorrhizal Group Department Biofertilizers and Plant Nutrition Instituto Nacional de Ciencias Agrícolas Gaveta Postal No 1 San José de Las Lajas 32700 Mayabeque Cuba

Department of Applied Sciences Faculty of Bioscience Engineering Ghent University 5 Vaerwyckweg 1 9000 Ghent Belgium

Department of Botany Center for Life Science and Health Federal University of Rio de Janeiro State Rio de Janeiro RJ 22290 255 Brazil

Mycorrhiza Laboratory Embrapa Agrobiologia BR 464 km 07 Bairro Ecologia Seropédica RJ 23891 000 Brazil

Plant Pathology Group Centro Nacional de Sanidad Agropecuaria Mayabeque Cuba

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