Surfactin-producing Bacillus velezensis 1B-23 and Bacillus sp. 1D-12 protect tomato against bacterial canker caused by Clavibacter michiganensis subsp. michiganensis

Bacillus strains are known to produce cyclic lipopeptides that are capable of providing protection against plant pathogens. Such abilities could be utilized to protect greenhouse tomatoes against diseases including bacterial canker caused by Clavibacter michiganensis subsp. michiganensis (Cmm). In the present study, Bacillus velezensis strain 1B-23 and Bacillus sp. strain 1D-12 were assessed for their potential biocontrol abilities against Cmm strain 98–1 (Cmm98–1). Both Bacillus strains interfered with growth of Cmm98–1 in vitro, as determined by agar plate assays to screen for microbial antagonism. Inoculation of Cmm98–1 infected tomato plants with B. velezenis 1B-23 or Bacillus sp. 1D-12 lead to significantly reduced disease incidence in a greenhouse setting. Liquid Chromatography coupled to Mass Spectrometry (LC-MS) of 1B-23 and 1D-12 extracts identified [Leu7]surfactin C13 (often called surfactin A), [Leu7]surfactin C14 (often called surfactin B) and [Leu7]surfactin C15 (often called surfactin C) in fractions of extracts that inhibited growth of Cmm98–1.