FUNGAL MICROBIOLOGY In Vivo Modulation of Arbuscular Mycorrhizal Symbiosis and Soil Quality by Fungal P Solubilizers Ivana F. Della Mónica 1,2 & Alicia M. Godeas 1 & José M. Scervino 1,3 Received: 20 March 2018 /Accepted: 5 June 2019 # Springer Science+Business Media, LLC, part of Springer Nature 2019 Abstract Phosphorus (P) is an essential nutrient with low bioavailability in soils for plant growth. The use of P solubilization fungi (PSF) has arisen as an eco-friendly strategy to increase this nutrient’s bioavailability. The effect of PSF inoculation and its combination with P-transporting organisms (arbuscular mycorrhizal fungi, AMF) on plant growth has been previously studied. However, these studies did not evaluate the combined effect of PSF and AMF inoculation on plant growth, symbiosis, and soil quality. Therefore, the aim of this study is to assess the impact of PSF on the AMF-wheat symbiosis establishment and efficiency, considering the effect on plant growth and soil quality. We performed a greenhouse experiment with wheat under different treatments (+/−AMF: Rhizophagus irregularis; +/−PSF strains: Talaromyces flavus, T. helicus L7B, T. helicus N24, and T. diversus) and measured plant growth, AMF root colonization, symbiotic efficiency, and soil quality indicators. No interaction between PSF and R. irregularis was found in wheat growth, showcasing that their combination is not better than single inoculation. T. helicus strains did not interfere with the AMF-wheat symbiosis establishment, while T. diversus and T. flavus decreased it. The symbiotic efficiency was increased by T. flavus and T. helicus N24, and unchanged with T. helicus L7B and T. diversus inoculation. The soil quality indicators were higher with microbial co-inoculation, particularly the alkaline phosphatases parameter, showing the beneficial role of fungi in soil. This work highlights the importance of microbial interactions in the rhizosphere for crop sustainability and soil quality improvement, assessing the effects of PSF on AMF-wheat symbiosis. Keywords Microbial interactions . Phosphatases . Phosphate-solubilizing fungi . Rhizophagus irregularis . Plant growth promotion . Talaromyces Introduction Crop productivity enhancement, one of the most challenging issues for supplying the increasing worldwide food demands, is highly dependent of phosphorus (P) availability in soils. This essential nutrient is generally found complexed with cations (Ca, Al, Fe, Mg) forming insoluble precipitates, unavailable for plant uptake, thus limiting yields [1]. To supply plant nutrient needs, traditional agriculture management commonly adds agro- chemicals, rendering contamination of soils, eutrophication of waters, and lowering of microbial biodiversity [2]. This negative impact on the agroecosystem could be decreased by applying eco-friendly alternatives such as the use of bioinoculants that maximize the soil nutrient availability and help the plants in a natural way to absorb them efficiently [3]. In soils, some fungal species can solubilize inorganic precipi- tated P and mineralize organic P making it accessible for plant uptake [4, 5]. These organisms are called P-solubilizing fungi (PSF). Previous reports have shown that PSF inoculation not only increased the soil P bioavailability but also promoted the plant growth and yields due to improved P uptake and release of plant growth hormones, siderophores, and biocontrol substances [6–9]. PSF inoculation can be combined with a soil-to-plant P- transporting group of microorganisms: the arbuscular * Ivana F. Della Mónica ivanadm@bg.fcen.uba.ar; ifdellamonica@gmail.com 1 Departamento de Biodiversidad y Biología Experimental, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Instituto de Biodiversidad y Biología Experimental y Aplicada (IBBEA) UBA-CONICET, Pabellón II, 4P Ciudad Universitaria, Intendente Güiraldes 2160, 1428 Buenos Aires, Argentina 2 Departamento de Biodiversidad y Biología Experimental, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Instituto de Micología y Botánica (INMIBO) UBA-CONICET, Pabellón II, 4P Ciudad Universitaria, Intendente Güiraldes 2160, 1428 Buenos Aires, Argentina 3 Instituto de Investigaciones en Biodiversidad y Medioambiente (INIBIOMA), CONICET-UNCo, Quintral 1250, 8400 San Carlos de Bariloche, Río Negro, Argentina Microbial Ecology https://doi.org/10.1007/s00248-019-01396-6