Fungal communities and functions response to long-term fertilization in paddy soils

Soil fungi play an important role in agricultural ecosystems, yet the understanding of the responses of fungi community and function to different fertilization is limited. Here we report the responses of fungal communities and functions to 34 years of application of inorganic fertilizer (NPK), rice straw combined with inorganic fertilizer (NPKS), and no fertilizer (CK). The fungal communities were identified by Illumina high-throughput sequencing and the functional groups were inferred with FUNGuild. Three predominant Phyla of Ascomycota, Basidiomycota, Zygomycota were identified in three treatments. A significantly lower proportion of Ascomycota (47%) but higher relative abundance of Basidiomycota (28%) were observed in the NPKS treatment compared with the CK (71% and 14%, respectively). A low proportion of Basidiomycota (10%), and no significant changes in Ascomycota (74%) were found in the NPK treatment in comparison to the CK (14% and 71%, respectively). The relative abundance of Zygomycota in the NPKS (8%) and NPK (9%) treatments were significantly higher than in the CK (5%). Diversity analysis showed that indexes including Shannon, Simpson, Chao 1 and ACE all significantly declined in NPK but increased in NPKS compared with CK. FUNGuild revealed that symbiotrophic fungi in the NPKS treatment (8%) were significantly higher than in the NPK (3%) and CK (3%) treatments, and dominated by the genera Redeckera and Tricholoma, the species Trichoderma atroviride and the order Scleroderma. However, a higher proportion of pathotrophic fungi in the NPK treatment (19%) were detected than in the NPKS (11%) and CK (10%) treatments, and dominated by the species Schizangiella serpentis. Redundancy analysis (RDA) showed that fungal community structure and function were more strongly related to moisture, EC and porosity in the soil. We suggest that the sole application of inorganic fertilizer results in great changes in fungal community composition and the hazard of excess growth of pathogenic fungi, whereas combined organic fertilizer and rice straw is beneficial to maintain a healthy ecological environment and the diversity of fungal communities in paddy soil.