Antagonistic activity and biocontrol effects of Streptomyces sp. CX3 cell-free supernatant against blueberry canker caused by Botryosphaeria dothidea

Botryosphaeria dothidea is a hazardous fungal pathogen that can cause blueberry canker worldwide. In this study, the modes of antagonism by cell-free supernatant (CFS) of Streptomyces sp. CX3 against B. dothidea was investigated and the biocontrol efficacy of CFS under field conditions was also evaluated. The in vitro bioassay results showed that CFS significantly suppressed the mycelium biomass and growth and disrupted the mycelium morphology of B. dothidea. CFS also had the ability to damage the plasma membrane of B. dothidea as evidenced by increased electrical conductivity in the culture medium and malonaldehyde (MDA) content of pathogen hyphae. The determination of key enzymes in glycolysis pathway showed that CFS significantly increased the activity of hexokinase (HK), fructose-6-phosphate kinase (FPK), and pyruvate kinase (PK) of B. dothidea. And, the significant reduce of glucose content and the accumulate of pyruvate content in B. dothidea treated with CFS further confirmed that CFS may accelerate the glycolysis metabolism of B. dothidea, which reduced the accumulation of energy and nutrients in pathogenic fungus. Results of field experiments indicated that CFS could effectively reduce the lesion area on blueberry branches, and the protective effect of CFS was superior to curative effect. To the best of our knowledge, this is the first report regarding the use of extracts from Streptomyces sp. to control blueberry canker caused by B. dothidea under field conditions.

Automated summary

This study found that the cell-free supernatant (CFS) of Streptomyces sp. CX3 has antagonistic effects against the blueberry canker pathogen Botryosphaeria dothidea. The CFS not only suppressed the growth and reproduction of the pathogen, but also damaged its plasma membrane, reducing the accumulation of energy and nutrients. Field experiments confirmed the efficacy of CFS in controlling blueberry canker.