A novel endophytic strain of Lactobacillus plantarum CM-3 with antagonistic activity against Botrytis cinerea on strawberry fruit

The fungal pathogen Botrytis cinerea causes grey mold, a severely damaging disease of strawberry. Lactic acid bacteria (LAB) are known for their biopreservative activity. Meanwhile, LAB dominate in plant organs over time, and are of pivotal importance for plant defense. The goal of the present study was to isolate endophytic LAB and to evaluate for their biocontrol activities against B. cinerea. Of the tested endophytic bacteria isolates, Lactobacillus plantarum CM-3 demonstrated the highest potential for in vitro and in vivo control of B. cinerea. The in vitro results showed that L. plantarum CM-3 reduced the mycelial growth of B. cinerea on Potato Dextrose Agar (PDA) between 55.27% and 79.80%. Spore germination of the pathogen was greatly inhibited in the presence of living cell suspensions. In in vivo biocontrol assays, the decay incidence and lesion diameter of grey mold decay of strawberries treated by L. plantarum CM-3 cells were significantly (P < 0.05) reduced compared with the control fruit. At concentrations of 1 x 10(8) and 1 x 10(9) CFU mL(-1), the incidence of gray mold was reduced by 48.23% and 75.00% respectively, compared to the control, after storage at 20 degrees C for 6 d. Moreover, rapid colonization of L. plantarum CM-3 in wounds was observed both in the presence or absence of B. cinerea at 20 degrees C during the storage period. The concentrations of the antagonist had significant effects on biocontrol effectiveness both in vitro and in vivo. However, cell-free filtrates of the strain failed to provide any protection against B. cinerea. Findings of the present study suggested that L. plantarum CM-3 could be a promising biocontrol agent for application during the post-harvest storage and marketing of horticultural products. This study reports the first assessment of endophytic LAB isolated from strawberry fruit and selection of isolates for the biocontrol of B. cinerea.