Pseudomonas exacerbates the apple replant disease induced by Fusarium

In this study, rhizosphere soils from apple trees continuously cropped were employed as materials, and the occurrence mechanism of Apple Replant Disease (ARD) was revealed from the microbiome through high-throughput sequencing, co-occurrence network, NetShift and correlation analysis. Core microbes were isolated, and their roles were verified through reinoculation experiments. The results indicated that the rhizosphere soil bacterial diversity of apples decreased and the fungal diversity increased, and the rhizosphere microbial network transformed from a "bacterial type" to a "fungal type". Pseudomonas might be a key soil genus in the occurrence of ARD, correlation analysis revealed for the first time that Pseudomonas was negatively correlated with bacterial diversity but positively correlated with Fusarium. Reinoculation experiments verified that adding key Pseudomonas ASVs indeed exacerbated the occurrence of replant diseases in strawberry and apple. The findings of this study provide new insights into the mechanism underlying the occurrence of ARD.

本研究以连作苹果树的根际土壤为实验材料，借助高通量测序、共现网络分析、NetShift以及相关性分析，从微生物组层面揭示苹果连作障碍（Apple Replant Disease, ARD）的发生机制。研究分离得到核心微生物，并通过重新接种实验验证其功能。结果显示，苹果根际土壤细菌多样性显著降低，真菌多样性则有所升高，根际微生物网络也从“细菌主导型”转变为“真菌主导型”。假单胞菌属（Pseudomonas）可能是ARD发生过程中的关键土壤菌群，相关性分析首次揭示：假单胞菌属与细菌多样性呈负相关，而与镰刀菌属（Fusarium）呈正相关。重新接种实验证实，添加关键的假单胞菌属扩增子序列变体（Amplicon Sequence Variants, ASVs）确实会加重草莓与苹果树的连作障碍发生程度。本研究结果为ARD的发生机制提供了全新的研究视角。