Effects of 6S-2 on Apple Tree Growth and Replanted Soil Microbial Environment.

strain 6S-2 with biocontrol effects and potential growth-promoting properties was made into a fungal fertilizer for the prevention of apple replant disease (ARD). 6S-2 fertilizer not only promoted the growth of Rehd seedlings in greenhouse and pot experiments, but also increased the branch elongation growth of young apple trees. The soil microbial community structure changed significantly after the application of 6S-2 fertilizer: the relative abundance of increased significantly, the relative abundance of (especially the gene copy numbers of four species) and decreased, and the relative abundance of and increased. The bacteria/fungi and soil enzyme activities increased significantly after the application of 6S-2 fertilizer. The relative contents of alkenes, ethyl ethers, and citrullines increased in root exudates of Rehd treated with 6S-2 fertilizer and were positively correlated with the abundance of . The relative contents of aldehydes, nitriles, and naphthalenes decreased, and they were positively correlated with the relative abundance of . In addition, levels of ammonium nitrogen (NH-N), nitrate nitrogen (NO-N), available phosphorus (AP), available potassium (AK), organic matter (SOM), and pH in rhizosphere soil were also significantly related to changes in the microbial community structure. In summary, the application of 6S-2 fertilizer was effective in alleviating some aspects of ARD by promoting plant growth and optimizing the soil microbial community structure.