Arbuscular mycorrhizal fungal communities in the rhizospheric soil of litchi and mango orchards as affected by geographic distance, soil properties and manure input

Utilization of arbuscular mycorrhizal (AM) resources to improve, or even maintain agroecosystem sustainability requires a thorough understanding of the biotic and abiotic factors that impact AM fungal communities. AM symbiosis is important in mango and litchi trees, two economically important fruit crops in China, but there is little information on the AM fungi associated with these trees or their responses to organic fertilizer. Using Illumina high-throughput sequencing we analyzed AM colonization, spore density, and community composition and diversity in the rhizospheric soil from 16 mango orchards and 16 litchi orchards located in southern China. Ours was a regional scale study and in general, we found that the majority of AM fungi OTUs belonged to the families Glomeraceae, followed by Gigasporaceae, Paraglomeraceae, Acaulosporaceae and Diversisporaceae. Glomus and Paraglomus were the genera that differed most in abundance between the rhizospheric soil of mango and litchi. AMF community composition was impacted by latitude and longitude and soil characteristics such as, NO3--N, NH4+-N, available-P, and soil organic carbon (SOC). The sampling sites were in areas of medium to low altitude, and there was no significant correlation between altitude and AM fungal richness. We found that higher soil nutrient content, particularly available-P, was negatively correlated with AM colonization. Our results also showed that some of the AM genera responded differently to environmental variables. Structural equation modeling (SEM) demonstrated that SOC not only had a direct positive effect on AMF richness, but also an indirect negative effect, due to increased soil fertility. Our findings have enabled a deeper insight into the impacts of organic fertilizer on AM fungal communities, which will be valuable when considering AM symbiosis in orchard management.