Abstract
Kiwifruit worldwide suffers from the devastating diseases of bacterial canker caused by Pseudomonas syringae pv. actinidiae (Psa) and gray mold caused by Botrytis cinerea. Here, an endophytic bacterium XL17 isolated from a rape crown gall was screened out for its potent antagonistic activities against Psa and B. cinerea. Strain XL17 and its cell-free culture filtrate (CF) inhibited the growth of Psa and B. cinerea, Psa-associated leaf necrosis, and B. cinerea-associated kiwifruit necrosis. Electron microscopy showed that XL17 CF could damage the cell structures of Psa and B. cinerea. Genome-based taxonomy revealed that strain XL17 belongs to Pseudomonas bijieensis within the P. corrugata subgroup of the P. fluorescens species complex. Among the P. corrugata subgroup containing 31 genomospecies, the presence of the phl 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 P. bijieensis XL17 producing DAPG and cyclic lipopeptides can be used to control bacterial canker and gray mold pathogens of kiwifruit.
Highlights
The genus Pseudomonas is one of the most complex and diverse genera among Gramnegative bacteria and consists of more than 300 species described to date [1]
The bacterial canker disease caused by Pseudomonas syringae pv. actinidiae (Psa) is the most prevalent and devastating pandemic disease of kiwifruit [6,7]
Psa strain ML2-12 was isolated from a bacterial canker stem of a kiwifruit plant grown in Taizhou, China
Summary
The genus Pseudomonas is one of the most complex and diverse genera among Gramnegative bacteria and consists of more than 300 species described to date (https://lpsn.dsmz.de/genus/pseudomonas, accessed on 2 October 2021) [1]. The genus Pseudomonas is one of the most complex and diverse genera among Gramnegative bacteria and consists of more than 300 species described to date Pseudomonas is ubiquitous in aquatic and terrestrial environments and in association with diverse hosts including plants and animals [1,2]. Among plant-associated Pseudomonas, both pathogenic and beneficial strains are reported in the same or different species. The P. syringae species complex contains plant pathogens of a wide range of plant species [3] while in Microorganisms 2022, 10, 425. Kiwifruit is susceptible to various pathogens that cause diseases at different growth stages, as well as after harvest. The bacterial canker disease caused by Pseudomonas syringae pv. Actinidiae (Psa) is the most prevalent and devastating pandemic disease of kiwifruit [6,7]. The gray mold disease caused by Botrytis cinerea is the most prevalent and devastating postharvest disease of kiwifruit, accounting for up to 30% of total postharvest losses in extreme cases [8,9]
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