The choice of rice rotation system affects the composition of the soil fungal community and functional traits

Plant rotation is a common practice in upland rice production. However, the effects of plant rotation on the interactions between rice plants, soil and underground ecosystems need to be studied further. Here, quantitative PCR and high-throughput pyrosequencing of the ITS region was applied to investigate the fungal abundance, diversity, and composition of fungal functional guilds in rice field soils and after different rotation practices ((rice-fallow (RF), rice-Chinese milk vetch (RV) and rice-wheat (RW)) and their relationship with rice yields. The results showed that the six-year RV and RW rotations increased fungal abundance by 42.7 %-69.2 % relative to RF, but decreased the soil bacterial-to-fungi ratio and fungal diversity. For the functional guilds, RV rotation significantly increased the relative abundance of soil saprotrophs and pathotrophs by 73.30 % and 32.94 %, respectively, while that of symbiotrophs was decreased by 35.96 %, compared to RF. RW rotation was found to significantly decrease all three fungal functional guilds, but increased the symbiotroph-saprotroph ratio. A structure equal model analysis indicated that the diversity of saprotrophs was significantly and negatively correlated with rice yield. Altogether, this work provides a detailed description of how the soil fungal community, including saprotrophic, symbiotrophic and pathotrophic functional guilds, responded to different upland rice rotation practices after eight years of application.