Zucchini Vein Clearing Disease Is Caused by Several Lineages Within <i>Pseudomonas syringae</i> Species Complex

Lacault, Caroline; Briand, Martial; Jacques, Marie‐Agnès; Darrasse, Armelle

doi:10.1094/phyto-07-19-0266-r

Cited by 4 publications

(41 citation statements)

References 49 publications

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“…In this study, eleven P. syringae isolates obtained from a zucchini disease outbreak in Australia [ 2 ] were compared to the publicly available genomes of P. syringae phylogroup 2. As these Australian isolates were determined to be P. syringae clade 2b, their genetic diversity and effector profile in relation to previous reports [ 3 , 11 ] will further inform the genetic basis of their observed phenotypes. Genome-wide association studies (GWAS) were performed to identify potential genes associated with adaptation to cucurbit hosts and unique genes in clade 2b-a.…”

Section: Introductionmentioning

confidence: 61%

“…Comparative genomics of virulence factors in the P. syringae complex have shown that strains from phylogroup 2 harbor fewer type III effectors (T3Es) but can produce more phytotoxins, compared to strains from the other primary phylogroups [ 6 – 8 ]. Over the last few years, many P. syringae strains in phylogroup 2 associated with Cucurbitaceae have been isolated and their genetic diversity, pathogenicity and host-association have been studied in detail [ 2 , 3 , 9 – 11 ]. Pan-genome association analysis of P. syringae phylogroup 2 cucurbit-infecting strains identified seven genes that potentially contribute to niche adaptation to cucurbit hosts including T3Es hopZ5 , hopA1 and its chaperone shcA , type VI secreted effector vgrG , and three uncharacterised proteins [ 3 ].…”

Section: Introductionmentioning

confidence: 99%

“…Pan-genome association analysis of P. syringae phylogroup 2 cucurbit-infecting strains identified seven genes that potentially contribute to niche adaptation to cucurbit hosts including T3Es hopZ5 , hopA1 and its chaperone shcA , type VI secreted effector vgrG , and three uncharacterised proteins [ 3 ]. The presence/absence of some effectors such as avrRpt2 , hopZ5 , hopC1 and hopH1 were predicted to be associated with host range susceptibility and virulence [ 11 ].…”

Section: Introductionmentioning

confidence: 99%

“…Clade 2b-a is a branch group within clade 2b [ 3 ] and consists of P. syringae isolated from Cucurbitaceae including pumpkin ( Cucurbita moschata ), melon ( Cucumis melo ), squash ( Cucurbita pepo ), watermelon ( Citrullus lanatus ) and zucchini ( Cucurbita pepo ) [ 2 , 3 , 9 – 11 ]. This clade emerged from genome-wide homologous recombination between clade 2a and 2b [ 3 ].…”

Section: Introductionmentioning

confidence: 99%

“…This clade emerged from genome-wide homologous recombination between clade 2a and 2b [ 3 ]. Three clusters (A, B and C) were identified in clade 2b-a with a unique effector profile on each cluster [ 11 ].…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

Comparative genomics and genomic diversity of Pseudomonas syringae clade 2b-a in Australia

Djitro

Roach²,

Mann

et al. 2022

BMC Microbiol

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Background A zucchini disease outbreak with unusual symptoms associated with Pseudomonas syringae clade 2b was identified in Bundaberg, Australia during autumn 2016. To investigate the genetic diversity of the 11 Australian isolates obtained from the outbreak, the genomes were compared to the publicly available P. syringae strains in phylogroup 2. Results Average nucleotide identity refined the P. syringae clade 2b-a into four clusters (Cluster A, B, C1 and C2), an expansion from the previously identified A, B and C. Australian isolates were in Cluster A, C1 and C2. Genomic analyses highlighted several key factors that may contribute to the virulence of these isolates. Six orthologous groups, including three virulence factors, were associated with P. syringae phylogroup 2 cucurbit-infecting strains. A region of genome plasticity analysis identified a type VI secretion system pathway in clade 2b-a strains which could also contribute to virulence. Pathogenicity assays on isolates KL004-k1, KFR003-1 and 77-4C, as representative isolates of Cluster A, C1 and C2, respectively, determined that all three isolates can infect pumpkin, squash, watermelon and zucchini var. Eva with different levels of disease severity. Subsequently, type III effectors were investigated and four type III effectors (avrRpt2, hopZ5, hopC1 and hopH1) were associated with host range. The hopZ effector family was also predicted to be associated with disease severity. Conclusions This study refined the taxonomy of the P. syringae clade 2b-a, supported the association between effector profile and pathogenicity in cucurbits established in a previous study and provides new insight into important genomic features of these strains. This study also provided a detailed and comprehensive resource for future genomic and functional studies of these strains.

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Section: Introductionmentioning

confidence: 61%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Comparative genomics and genomic diversity of Pseudomonas syringae clade 2b-a in Australia

Djitro

Roach²,

Mann

et al. 2022

BMC Microbiol

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Characterization of Pseudomonas syringae Isolated from Systemic Infection of Zucchini in Australia

Djitro

Roach²,

Mann

et al. 2022

Plant Disease

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Zucchini plants, with symptoms including twisted petioles, necrotic leaves, crown-rot and internal fruit-rot, were found in Bundaberg, Australia at a commercial field for the first time during late autumn 2016, resulting in direct yield losses of 70 to 80%. Three Pseudomonas syringae strains that isolated from symptomatic leaf (KL004-k1), crown (77-4C) and fruit (KFR003-1) were characterised and their pathogenicity evaluated on pumpkin, rockmelon, squash and zucchini. Biochemical assays showed typical results for P. syringae. The three isolates differed, however, in that two produced fluorescent pigment (KFR003-1 and 77-4C) whilst the third, KL004-k1, was non-florescent. Multi-locus sequence analysis classified the isolates to phylogroup 2b. The SNP analysis of core genome from the Australian and closely related international isolates of P. syringae showed two separate clusters. The Australian isolates were clustered based on fluorescent phenotype. Pathogenicity tests demonstrated all three isolates moved systemically within the inoculated plants and induced necrotic leaf symptoms in zucchini plants. Their identities were confirmed with specific PCR assays for P. syringae and phylogroup 2. Pathogenicity experiments also showed the Eva variety of zucchini was more susceptible than Rosa for all three isolates. Isolate KL004-k1 was more virulent than 77-4C on pumpkin, rockmelon, squash and zucchini. This study expands the knowledge of P. syringae isolates that infect cucurbits and provides useful information for growers about the relative susceptibility of a range of cucurbit species.

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Development of Tools to Detect and Identify Strains Belonging to the Pseudomonas syringae Species Complex Responsible for Vein Clearing of Zucchini

Lacault,

Briand,

Jacques

et al. 2024

PhytoFrontiers™

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Vein clearing of zucchini (VCZ) is a disease caused by seedborne bacteria that affects young plants of Cucurbita pepo subsp. pepo. VCZ agents are distributed into four phylogenetic clusters within clades 2a and 2ba of phylogroup 2 of the Pseudomonas syringae species complex. All these strains are pathogenic to squash, but only certain strains can also attack melon and cucumber. Strains belonging to clades 2b and 2d are sometimes isolated from zucchini seeds but have not been associated with VCZ epidemics. Identification tools for VCZ agents are required to improve disease control. Primers were designed to implement a seven-gene multilocus sequence analysis (MLSA) scheme for a collection of 60 strains isolated from zucchini seeds. The MLSA showed a clear predominance of strains of cluster 2ba-A and the presence of VCZ strains in a fifth cluster (2ba-C). PCR tests were designed to characterize strains in the VCZ clusters, and a multiplex qPCR test was proposed to distinguish strains with a cucurbit host range extended to melon and cucumber, harboring hopZ5 and sylC, from other strains harboring avrRpt2 and sylC. Additional qPCR tests were also designed to gain insights into clade-2b and -2d strains that can be isolated from cucurbits. These tools evaluated in silico with the NCBI database and experimentally with a collection of 112 strains detected all target strains, except for the test dedicated to clade-2b strains, and excluded 96.7 to 100% of nontarget strains. These tools are intended to serve phylogenetic studies, epidemiological monitoring, and seed testing. [Formula: see text] Copyright © 2024 The Author(s). This is an open access article distributed under the CC BY 4.0 International license .

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Zucchini Vein Clearing Disease Is Caused by Several Lineages Within Pseudomonas syringae Species Complex

Cited by 4 publications

References 49 publications

Comparative genomics and genomic diversity of Pseudomonas syringae clade 2b-a in Australia

Comparative genomics and genomic diversity of Pseudomonas syringae clade 2b-a in Australia

Characterization of Pseudomonas syringae Isolated from Systemic Infection of Zucchini in Australia

Development of Tools to Detect and Identify Strains Belonging to the Pseudomonas syringae Species Complex Responsible for Vein Clearing of Zucchini

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