Pseudomonas bijieensis Strain XL17 within the P. corrugata Subgroup Producing 2,4-Diacetylphloroglucinol and Lipopeptides Controls Bacterial Canker and Gray Mold Pathogens of Kiwifruit

Abstract

Kiwifruit worldwide suffers from the devastating diseases of bacterial canker caused by <i>Pseudomonas syringae</i> pv. <i>actinidiae</i> (Psa) and gray mold caused by <i>Botrytis cinerea</i>. Here, an endophytic bacterium XL17 isolated from a rape crown gall was screened out for its potent antagonistic activities against Psa and <i>B. cinerea</i>. Strain XL17 and its cell-free culture filtrate (CF) inhibited the growth of Psa and <i>B. cinerea</i>, Psa-associated leaf necrosis, and <i>B. cinerea</i>-associated kiwifruit necrosis. Electron microscopy showed that XL17 CF could damage the cell structures of Psa and <i>B. cinerea</i>. Genome-based taxonomy revealed that strain XL17 belongs to <i>Pseudomonas bijieensis</i> within the <i>P. corrugata</i> subgroup of the <i>P. fluorescens</i> species complex. Among the <i>P. corrugata</i> subgroup containing 31 genomospecies, the presence of the <i>phl</i> operon responsible for the biosynthesis of the phenolic polyketide 2,4-diacetylphloroglucinol (DAPG) and the absence of the lipopeptide/quorum sensing island can serve as the genetic marker for the determination of a plant-protection life style. HPLC detected DAPG in extracts from XL17 CF. MALDI-TOF-MS analysis revealed that strain XL17 produced cyclic lipopeptides of the viscosin family and orfamide family. Together, phenotypic, genomic, and metabolic analyses identified that <i>P. bijieensis</i> XL17 producing DAPG and cyclic lipopeptides can be used to control bacterial canker and gray mold pathogens of kiwifruit.