The biocontrol potential of Streptomyces polychromogenes YKL‐11 against apple replant disease: Inhibition of the growth of pathogenic Fusarium and remodelling of soil microbial flora

Apple replant disease (ARD) severely restricts the sustainable development of the apple industry. Streptomyces is important for the development of biocontrol bacteria for plant diseases and has broad prospects for use in agriculture. This study focused on Fusarium, one of the main pathogens involved in the development of ARD. The antagonistic strain Streptomyces polychromogenes YKL-11 was isolated from the rhizosphere soil of healthy apple trees in old orchards. High-throughput sequencing was used to investigate the effects of YKL-11 on the microbial community in replanted soil, and its biocontrol efficacy was evaluated through pot and field experiments. YKL-11 can significantly erode and disrupt the mycelial structure of Fusarium, causing its spores to atrophy and deform, thereby efficiently inhibiting the growth of this fungus. The results of the pot experiment showed that the application of YKL-11 could significantly promote the growth of apple seedlings, while effectively reducing the soil population of Fusarium oxysporum, F. moniliforme, F. solani and F. proliferatum. A microbiome analysis revealed that YKL-11 optimizes the microbial community. Composition in replanted soil by enriching beneficial genera such as Chaetomium and Trichoderma while inhibiting harmful genera, including Fusarium, Cephalotrichum and Neocosmospora. Overall, S. polychromogenes YKL-11 can effectively alleviate ARD. The results of this study provide a new theoretical basis and practical ideas for the green biological control of ARD.