Despite the known influence of continuous cropping on soil microorganisms, little is known about the associated difference in the effects of continuous cropping on the community compositions of soil bacteria and fungi. Here, we assessed soil physicochemical property, as well as bacterial and fungal compositions across different years (Uncropped control, 1, 6, 11, 16, and 21 years) and in the watermelon system of a gravel mulch field in the Loess Plateau of China. Our results showed that long-term continuous cropping led to substantial shifts in soil bacterial and fungal compositions. The relative abundances of dominant bacterial and fungal genera (average relative abundance > 1.0%) significantly varied among different continuous cropping years (P < 0.05). Structural equation models demonstrated that continuous cropping alter soil bacterial and fungal compositions mainly by causing substantial variations in soil attributes. Variations in soil pH, nutrient, salinity, and moisture content jointly explained 73% and 64% of the variation in soil bacterial and fungal compositions, respectively. Variations in soil moisture content and pH caused by continuous cropping drove the shifts in soil bacterial and fungal compositions, respectively (Mantel R = 0.74 and 0.54, P < 0.01). Furthermore, the variation in soil bacterial and fungal composition showed significant correlation with watermelon yield reduction (P < 0.01). Together, long-term continuous cropping can alter soil microbial composition, and thereby influencing watermelon yield. Our findings are useful for alleviating continuous cropping obstacles and guiding agricultural production.

During an investigation of fungicolous fungi associated with mushrooms in China, four boleticolous fungi were collected from Sichuan Province. Based on the morphological features and multi-gene phylogenetic analyses this study introduces two new species, Hypomyces ampullaris, and H. sichuanensis. The new species are described and illustrated comprehensively and compared with their related fungi. Hypomyces ampullaris is similar to Sepedonium ampullosporum in forming candelabrum-like conidiophores and producing ampulliform conidia but differs from the latter in having shorter phialides and smaller ampulloconidia. Hypomyces sichuanensis is similar to H. chrysospermus, H. microspermus, and Sepedonium laevigatum in forming poorly developed verticills conidiophores and the shape and size of aleurioconidia. However, the asexual spores of H. sichuanensis averaged somewhat smaller than those of H. chrysospermus and S. laevigatum, and larger than that of H. microspermus. Additionally, H. ampullaris and H. sichuanensis distinct from their close relatives in no pigment discoloration of the PDA medium. These species introduced here, improve our understanding of the diversity of Hypomyces, especially of the boleticolous Hypomyces in China.