Mycorrhizas Mitigate Soil Replant Disease of Peach Through Regulating Root Exudates,Soil Microbial Population,and Soil Aggregate Stability

Soil replant disease is the main bottleneck interfering with tree growth of peach in soils with poor traits. A potted study was conducted to evaluate the effects of inoculation with an arbuscular mycorrhizal fungus (AMF), Acauloapora scrobiculata, on plant growth, mineral nutrients, soil enzyme activities, soil microbial populations, and root exudate compositions of peach (Prunus persica L. Batsch) seedlings grown in replant soil and non-replant soil. After 15 weeks in AMF inoculation, replant soil heavily inhibited root mycorrhizal colonization. In replant soil, AMF inoculation significantly increased shoot biomass and root phosphorus, potassium, calcium, copper, zinc, iron, and boron concentrations. Mycorrhizal peach seedlings showed a higher number of soil bacteria and total microbes but a lower number of soil fungi under replant conditions, as well higher soil urease and acid phosphatase activity and lower soil sucrase and catalase activity. Greater soil aggregate stability was observed in mycorrhiza-inoculated replant soil than in non-mycorrhizal soil due to the increase of water-stable aggregates in 2–4 mm and 1–2 mm size. In addition, a total of 92 substances were identified in root exudates, and the mycorrhizosphere had considerably more root exudate compositions. AMF inoculation had a significantly inhibitive effect on the relative abundance of allelochemical substances, including benzoic acid, benzaldehyde, diisooctyl phthalate, phenols, and sterols, while there was an increase in diphenyl-ethanedione and à-(benzoyloxy)-benzeneacetonitrile in replanted peach. It was concluded that AMF inoculation could partly mitigate soil replant disease of peach through modulating soil microbe balance, improving soil aggregate stability, and changing root exudate compositions.