Biological control of Pseudomonas syringae pv. aptata on sugar beet with Bacillus pumilus SS-10.7 and Bacillus amyloliquefaciens (SS-12.6 and SS-38.4) strains

Aim: Assessment of biological control of Pseudomonas syringae pv. aptata using crude lipopeptide extracts (CLEs) of two Bacillus amyloliquefaciens strains (SS-12.6 and SS-38.4) and one Bacillus pumilus strain (SS-10.7).

Methods and results: The minimum inhibitory concentration (MIC) of CLEs and their combinations against the pathogen and potential interaction between the extracts were determined in vitro. The most effective antibacterial activity was achieved with the CLE from B. amyloliquefaciens SS-12.6, with an MIC value of 0·63 mg ml^-1 . Interactions between CLE combinations were mostly indifferent. The biocontrol potential of CLEs, mixtures of CLEs, and cell culture of B. amyloliquefaciens SS-12.6 was tested on sugar beet plants inoculated with P. syringae pv. aptata P53. The best result in inhibiting the appearance of tissue necrosis (up to 92%) was achieved with B. amyloliquefaciens SS-12.6 cell culture.

Conclusion: This work demonstrated significant biocontrol potential of the CLE and cell culture of B. amyloliquefaciens SS-12.6 which successfully suppress leaf spot disease severity on sugar beet plants.

Significance and impact of the study: The findings of biocontrol of sugar beet emerging pathogen will contribute to growers in terms of alternative disease control management. This study represents first assessment of biological control of P. syringae pv. aptata.