Biocontrol activity and patulin-removal effects of Bacillus subtilis, Rhodobacter sphaeroides and Agrobacterium tumefaciens against Penicillium expansum.

AIMS

This study was conducted to evaluate the biocontrol potential of Bacillus subtilis CICC 10034, Rhodobacter sphaeroides CGMCC 1.2182 and Agrobacterium tumefaciens CGMCC 1.2554 against patulin (PAT)-producer Penicillium expansum and their ability to remove PAT.

METHODS AND RESULTS

Bacillus subtilis effectively inhibited P. expansum both on apples and in in vitro experiments, which reduced the rot diameter on apples by 38% compared with the control. The reduction was followed by those induced by A. tumefaciens (27·63%) and R. sphaeroides (23·67%). None of the cell-free supernatant (CFS) was able to prevent pathogen growth. Three antagonists could suppress PAT production by P. expansum on apples by 98·5, 93·7 and 94·99% after treatment with B. subtilis, R. sphaeroides and A. tumefaciens respectively. In addition, the three strains led to a 0·56-1·47 log CFU g reduction in colony number of P. expansum on apples. Survival of antagonists on apple wounds revealed their tolerance to PAT. Furthermore, both live and autoclaved cells of three strains efficiently adsorbed artificially spiked PAT from medium.

CONCLUSIONS

The selected antagonists could be applied before harvesting to control apple infection by PAT-producing fungi and also during processing to act as PAT detoxifiers.

SIGNIFICANCE AND IMPACT OF THE STUDY

Since little information related to the capability of R. sphaeroides and A. tumefaciens to inhibit P. expansum is currently available, the results of this study provide some new perspectives to the biocontrol field.