Microbial interactions: effect of biocontrol and P solubilizing fungi in pre-symbiotic stages of arbuscular mycorrhizal fungi.

Abstract

Microbial interactions: effect of biocontrol and P solubilizing fungi in pre-symbiotic stages of arbuscular mycorrhizal fungi. Phosphorus (P) is an essential macronutrient with a low bioavailability in soils, thus limiting the plant growth. The use of P solubilizing fungi (HS) is a promising alternative to increase the efficiency of P-fertilizers. However, it is not fully understood if HS have antagonist effects on beneficial soil microbiota, such as arbuscular mycorrhizal fungi (HMA). This work studies the effect of HS with biocontrol abilities against phytopathogenic fungi on the pre-infective stages development of HMA, the first step in mycorrhizal root colonization. Spores of the HMA Gigaspora rosea were exposed in vitro to different exudate concentrations (0; 0,01; 0,1; 1; 3%) of different HS fungal strains (Talaromyces helicus strain L7B, T. helicus strain N24, T. diversus and Penicillium purpurogenum) in a system containing semi-liquid medium. Spores germination, elongation, ramification and morphology of the pre-infective mycelium of HMA were evaluated. We observed that only T. diversus increased germination while T. helicus L7B promoted the elongation, ramification and produced changes in the mycelial morphology without affecting spores’ germination. These results showed that germination and pre-infective development of G. rosea can be modified in length and ramification as a function of the identity of the HS strain used, suggesting that microbial interactions can positively impact on plant P nutrition through the modification of the previous stage to mycorrhizal symbiosis.