[Identification of Pantoea agglomeran XM2 with biocontrol activity against postharvest pear black spot].

OBJECTIVE: We isolated the bacterial strain XM2 from prunes (Prunus domestica L.) fruit surface. XM2 was identified and tested as an antagonist for postharvest biological control of black spot disease (Alternaria alternata) on pear fruits. METHODS: Strain XM2 was identified according to its morphological, physiological and biochemical characteristics and 16S rDNA sequence analysis. Inhibition tests were performed in wounds of pear fruits using different types of XM2 inocula, different concentration and inoculation time of XM2 and A. alternata. Effect of XM2 on mycelia morphology of A. alternata was observed under microscope. RESULTS: Strain XM2 was identified as Pantoea agglomeran. Biological control of XM2 against black spot disease was significantly better than the control, and the best inhibitory was observed when inoculated with suspension (97.73% of control effect). Higher XM2 concentration and lower A. alternata concentration showed better inhibitory effect. Similarly, the earlier inoculation of XM2 than A. Alternata, the better inhibitory effect on disease development. Microscopic observation found that XM2 broke part of the mycelia, making cell contents spilled and hyphae distorted. CONCLUSION: Pantoea agglomeran XM2 has the potential as an effective antagonist against postharvest pear blank spot disease.