Screening and identification of epiphytic and soil bacteria beneficial in the control of postharvest apple disease

This study aimed to isolate and evaluate bacterial strains with the potential to control storage diseases of apple trees. A total of 2,027 bacterial isolates were obtained from the phyllosphere of apple, strawberry, raspberry, and grape plants, as well as from soil associated with apple, strawberry, and raspberry crops. Screening using a dual-plate confrontation assay identified 1,678 isolates with antagonistic activity against Botrytis cinerea , the causative agent of grey mold. Subsequent testing on apple fruit enabled the selection of 13 isolates exhibiting the highest biocontrol efficacy. These isolates were identified as belonging to the species Serratia inhibens (22ZK, 24PK, 132M), Pseudomonas laurylsulfativorans (131M), Pseudomonas alvandae (133M), Pantoea agglomerans (T16/8, M13/07), Pantoea allii (T14/15, T08/33, T08/48), and Pantoea ananatis (T5/1, T14/1A, T14/8). The five most effective isolates (T5/1, T14/15, T16/8, T14/1A, and M13/07) reduced disease severity by 62.4% to 78.6%.Further antagonism assays against revealed that the selected isolates, besides B. cinerea also strongly inhibited growth of Monilinia fructigena and Colletotrichum acutatum in vitro.Pathogenicity tests confirmed that none of the 13 isolates induced hypersensitive reactions on tobacco or caused rot in potato tissues. However, five isolates (T08/33, T08/48, T5/1, T14/8, and T14/1A) were pathogenic in the red onion scale assay.