The Ectomycorrhizosphere Effect Influences Functional Diversity of Soil Microflora

Abstract

The aims of this study were to determine whether the microbial activities in soil compartments are influenced by ectomycorrhizal symbiosis and to determine the functional diversity of fluorescent pseudomonads associated with the symbiosis of Uapaca sp. and ectomycorrhizal fungi. Uapaca sp. seedlings were cultured in soils collected under ectomycorrhizal tree species (Afzelia africana, Isoberlinia doka and Uapaca somon) in southwestern Burkina Faso. After 8 months of culture, the soil highly colonized by hyphae (hyphosphere soil, HS), as well as the non-colonized soil (bulk soil, BS) was sampled from each pot. The non-mycorrhizal and mycorrhizal short roots with their adherent soil were collected and vigorously shacked, to recover the rhizosphere soil (RS) and the mycorrhizosphere soil (MS). The patterns of in situ catabolic potential of microbial communities were measured. Results showed that the functional activities of soil microbial communities were mainly dependent on ungal activities. In addition, this effect was different between the hyphosphere and mycorrhizosphere zones. The number of fluorescent pseudomonads was significantly higher in the HS, MS and RS compartments than in the bulk soil. The highest size of fluorescent pseudomonad population was in the HS compartment. The ectomycorrhizal symbiosis has also modified the functional activities of fluorescent pseudomonads. This fungal qualitative effect was mainly detected in the HS compartment on the ability of fluorescent pseudomonads to solubilize tricalcium orthophosphate and to produce lipases. Close interactions occur between the ectomycorrhizal symbiosis and the soil bacterial communities that could increase the efficiency of the fungal symbiosis for the host plant development.