Shifts in soil microbial diversity and functions during continuous cropping of strawberry

Soil microbial community is particularly essential in the sustainable cropping systems, which may partially account for the vulnerability of soils in continuous cropping (CC). However, the succession patterns and drivers of microbial communities in CC strawberry fields need to be further elucidated. Shifts in the structure and function of soil bacteria and fungi during strawberry CC (0, 2, 5, 15, and 18 years) were investigated using the Illumina MiSeq sequencing technology. The results demonstrated declines in diversity, richness index, and bacterial/fungal ratios in long-term CC soils. Variance partition analysis identified pH, available nitrogen, and available phosphorus as primary environmental factors affecting bacterial communities, whereas pH, available potassium, and available phosphorus dominated fungal communities. During strawberry CC, the relative abundances of the major genera Bacillus, Trichoderma, and Arthrobotrys first rose and then declined, while those of the other main genera Sclerotiniaceae and Fusarium gradually rose. Furthermore, the microbial functional annotation revealed that CC significantly altered the functional microbial flora, with a marked decrease in the relative abundance of arbuscular mycorrhizal fungi, but an increase in those of potential plant fungal pathogens in CC soils. The structural equation model revealed that CC significantly affected pH and potential plant fungal pathogens, with a standardized total effects of -0.77 and 0.82, respectively. Thus, strawberry CC significantly altered soil physicochemical properties, microbial communities and functions. These results provide theoretical guidance for the ecological restoration of strawberry CC sickness.