Potential of natamycin in enhancing the antagonistic activity ofBacillus amyloliquefaciensBGP20 against post-harvest bacterial soft rot of green pepper

Bacillus amyloliquefaciens BGP20 is a promising antagonist in controlling post-harvest bacterial soft rot of vegetables caused by Erwinia carotovora subsp. carotovora (Ecc). The objective of this study was to screen a kind of natural and safe additive which could enhance the bio-control activity of BGP20 against post-harvest bacterial soft rot of green pepper. The results of this study indicated that the additive natamycin had stronger inhibition against the pathogen Ecc compared with bamboo vinegar and chitosan in the 2× Yeast extract and Tryptone (2YT) medium. However, natamycin had a slight negative effect on the growth of BGP20 in the 2YT medium. In preventative treatments, natamycin significantly improved the bio-efficacy of BGP20, and enhanced its competitive position against Ecc in the wounds of green pepper. Compared with the treatment with BGP20 alone, the viable count of BGP20 after 72 h of incubation increased by 115.8% in the wounds of green pepper treated with BGP20 and 0.1% natamycin, while that of Ecc decreased by 92.1%. In addition, natamycin remarkably promoted the flocculation of Ecc cells in the 2YT medium, while promoting the dispersion of BGP20. Natamycin had no negative effects on the spore germination of BGP20 and its shelf life. These results indicated that natamycin had perfect compatibility with the antagonist BGP20, and it had a great potential in enhancing the bio-control activity of BGP20 against post-harvest bacterial soft rot of green pepper in preventative treatments.