Design and Evaluation of Synthetic Microbial Communities for Effective Fire Blight Disease Control in Apples

Fire blight disease caused by <i>Erwinia amylovora</i> has resulted in extreme economic losses to industrial plants of the Rosaceae family, including apples and pears, since the 1870s. Many countries have used pesticides and bactericides to manage the fire blight disease. However, chemical management leads to the emergence of a pesticide-resistant pathogen population. Therefore, attempts at managing the fire blight disease have been developed and applied using selected microorganisms as a biological control. However, a single strain of the biological control agent showed limited effect in reducing the disease. Here, we designed synthetic microbial communities (SynCom), which involve reconstituting multi-strains rather than relying on a single strain to enhance the disease control efficiency. We constructed the SynCom based on three categorized functions: i) anti-EA strain, ii) keystone taxa in healthy apples, iii) abundant metabolite strain in healthy apples than the fire blight infected apples. SynCom was significantly efficient in suppressing fire blight, achieving 0% disease severity in apple fruits, 1.67% in roses, and 5.4% in apple plants. Our finding presented that the well-designed SynCom showed significant effects in controlling the fire blight disease. Additionally, SynCom members should be selected based on multiple functions to maximize the impact on crop management.