Synergistic antibacterial activity of and phage MATE 2 for an effective biocontrol strategy against black rot disease in broccoli.

Black rot, caused by pv. (), is considered the most destructive disease affecting cruciferous vegetables, resulting in significant losses worldwide. The need for biocontrol agents against that can reduce reliance on chemical pesticides, enhance sustainability, and ensure crops and environmental health is crucial. Combining phages with other antibacterial agents (i.e., antibiotics and bacteriocins) to treat bacterial infections is gaining increased attention due to the frequently observed synergistic effects. This study introduces for the first time the combination of a lytic phage, i.e., phage MATE 2 (MATE 2) with nisin-producing subsp. () bacterium as an eco-friendly, cost-effective, and practical strategy for controlling in cruciferous vegetables. The antibacterial efficacy of MATE 2 and , individually and in combination, against was investigated through a series of assays and experiments conducted on broccoli plants. The time-killing curves results showed that under conditions of reduced population concentration (10 CFU/mL), MATE 2 at 10 PFU/mL exerted a persistent inhibitory effect on growth for 7 days. The Spot assays and v-qPCR analysis showed that both and its bacteriocin nisin have significant antibacterial potential to contrast . Furthermore, combined application of MATE 2 and in broccoli plants by foliar spraying generated significant synergistic efficacy in preventing infections, achieving a 71% reduction in symptoms, compared with 64 and 38% for single applications, respectively. In this study, the positive synergistic effect of the combined application of phage and beneficial bacteria in preventing black rot disease underscores this eco-friendly and cost-effective approach as a promising control measure against plant bacterial diseases.