Preparation of composite microbial culture and its biocontrol effect on apple replant disease

Antagonistic Bacillus sp. (Bacillus amyloliquefaciens QSB-6, Bacillus vallismortis HSB-2, Bacillus licheniformis XNRB-3, Bacillus velezensis XC1, Bacillus siamensis 2RS-9, Bacillus subtilis 4R-5, and Bacillus atrophaeus 9R-5) with common pathogens (Fusarium oxysporum, Fusarium solani, Fusarium proliferatum, Fusarium moniliforme, Alternaria alternata, Rhizoctonia solani, Albifimbria verrucaria, Phoma asparagi, and Phytophthora cactorum) which cause apple replant disease (ARD) were screened, and a composite microbial culture was prepared. The composite bacterial broth fermentation conditions were optimized by single factor and orthogonal experiments. When 2.6 × 109 amount composite microbial culture (at CFU·g−1) was added to the soil together with manure carrier (cow manure:straw=3:1) (T3), it significantly increased the biomass of Malus hupehensis Rehd. seedlings and young apple trees (Fuji New2001/M9T337), the population of soil bacteria, and activities of antioxidant enzymes as well as soil enzymes, and significantly reduced the population of soil fungi and the abundance of Fusarium sp. In conclusion, composite microbial culture could thus be used as a biological control agent for the management of ARD.