Key indicators for renewal and reconstruction of perennial trees soil: Microorganisms and phloridzin.

Perennial tree soil inhibits the growth of replanting apples, but the mechanism that underlies this inhibition is poorly understood. A total of 57 perennial tree soils were selected for the collection of soil samples in the Bohai Bay in May 2018. The severity of apple replant disease (ARD) for each soil was determined by calculating the rate of inhibition of growth replanted apple trees. A high-throughput sequencing analysis of internal transcribed spacer (ITS) was used to determine the soil fungal community. A correlation analysis was used to determine the relationship between the rate of inhibition of apple growth and soil factors. The degree of inhibition of plant growth varied substantially among the 57 soil samples examined. Different perennial tree soils have varying degrees of ARD. There was no significant difference in the composition of fungal community at the phylum level, but the genus level differed substantially. The abundances of Fusarium and Mortierella species and the contents of phloridin in the soil and soil organic matter (SOM) were significantly correlated with ARD severity. Structural equation modeling also emphasized that the degree of occurrence of ARD was directly or indirectly affected by Fusarium, Mortierella, phloridin and SOM. A correlation analysis can only be used as an indicator, and further research is merited to reveal how soil parameters affect ARD.