Soil Microbial Community Submitted to Heating Decreases the Mycorrhizal Association with Brachiaria Roots

In highly weathered tropical soils, phosphorus (P) is not widely available and present low mobility, which become the symbiotic associations between the root and arbuscular mycorrhizal fungi (AMF) a beneficial nutrient soil exploration strategy for P acquisition. In general, microbial community interacts strongly with AMF, affecting mycorrhizal colonization in host plants. The objective was to understand how changes in the soil microbial dynamics effect in the root colonization by AMF. The experiment was conducted in a glasshouse with brachiaria (Brachiaria brizantha) inoculated with three AMF species: Rhizophagus clarus; Dentiscutata heterogama; Acalouspora colombiana. The plants were cultivated under different levels of microbial diversity: natural soil (30ºC), and from this soil was obtained the soil microbial treatments submitted to a heat (50, 80 or 100ºC for one hour). The root sampling was made at 30 days after inoculation with AMF, and mycorrhizal colonization rate was evaluated. The lowest rates of mycorrhizal colonization were observed when AMF was not inoculated compared to treatments where AMF spores were inoculated. When spores of A. colombiana were inoculated in natural soil (30ºC), brachiaria roots presented an average of 54% colonization, while 2% of colonization was observed in soil treated at 100ºC. When inoculated with R. clarus and D. heterogama, brachiaria presented 38% and 43% of colonization rate, respectively, when cultivated in natural soil (30ºC). In these cases, lower levels of colonization were obtained along the heat treatment scale. These results show that each AMF species has a particular dependence of the soil microbiota to properly establish the connection with the plants.