Genetic patterns reveal historical and contemporary dispersal of a tree pathogen

Sakalidis, Monique L.; Feau, Nicolas; Dhillon, Braham; Hamelin, Richard

doi:10.1007/s10530-016-1120-7

Cited by 18 publications

(22 citation statements)

References 71 publications

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“…The detection of S. musiva in woody tissue is important for three reasons: (i) pathogen spread is linked to the movement of dormant cuttings (Goss et al ., ; Carnegie & Cooper, ; Sakalidis et al ., ); (ii) the low detection efficiency of current diagnostic approaches (Waterman, ; Stanosz & Stanosz, ; Feau et al ., ; Weiland & Stanosz, ); and (iii) the apparent presence of the pathogen in symptomless hosts (Waterman & Aldrich, ). To address these needs, a qPCR assay was developed capable of detecting and quantifying S. musiva in poplar stems.…”

Section: Discussionmentioning

confidence: 99%

“…The distribution of S. musiva has expanded with the spread of hybrid poplar plantations across North America and around the world (Callan et al ., ; Dos Santos et al ., ; Sakalidis et al ., ). The movement of S. musiva has been facilitated by the exchange of dormant cuttings between private and public breeding programmes, across international borders, for decades (Sakalidis et al ., ). Pathogen detection is a critical early step for successful disease management.…”

Section: Introductionmentioning

confidence: 97%

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Multiplex qPCR for detection and quantification of Sphaerulina musiva in Populus stems

2018

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Septoria canker is one of the major limiting factors in the use of hybrid poplar in agroforestry. The use of qPCR for quantification of fungal biomass in host tissue following infection can improve the speed and accuracy of both detection and phenotyping, potentially improving the management of this disease. This study reports the use of a multiplexed hydrolysis probe qPCR assay to detect and quantify the pathogen Sphaerulina musiva in artificially inoculated and naturally infected Populus trees. Species‐specific probes and primers were designed based on conserved gene sequences of S. musiva β‐tubulin and Populus spp. eukaryotic initiation factor IV (eIF4AII). Experiments were performed on greenhouse‐inoculated poplar stems at 1, 3 and 7 weeks post‐inoculation. The qPCR assay detected significant differences among clones and isolates in symptomless samples after 1 week. These differences were not apparent by visual phenotyping. The assay also detected differences among isolates, collected from a range of geographic locations, 3 weeks post‐inoculation. For naturally infected samples, the S. musiva detection rate ranged from 92% to 100%. The primers also proved robust for direct endpoint PCR‐based detection of S. musiva spores, with a minimum detection threshold of 10 spores. The primers proved to be sensitive and specific for S. musiva detection, making them a useful tool for diagnostics and comparisons among isolates and clones in the early stages of infection.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 97%

Multiplex qPCR for detection and quantification of Sphaerulina musiva in Populus stems

2018

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“…Transport of infected planting material is suggested to have enabled the spread of the pathogen across the North American continent (Sakalidis et al, 2016). Transport of infected planting material is suggested to have enabled the spread of the pathogen across the North American continent (Sakalidis et al, 2016).…”

Section: Spreadmentioning

confidence: 99%

Pest categorisation of Sphaerulina musiva

Jeger¹,

Bragard²,

Caffier³

et al. 2018

EFS2

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“…As another explanation, we cannot exclude the possibility that the observed lack of differentiation in the used marker is due to human activities. The exchange of tree material may possibly initiate/sustain gene flow between geographically distant pathogen populations, even if the pathogen is incapable of dispersing over long distances (Sakalidis, Feau, Dhillon, & Hamelin, 2016). For Septoria musiva, a pathogen causing stem cankers as well as leaf spot disease (and a close relative of S. populicola), a range expansion was facilitated by human activities (Sakalidis et al, 2016).…”

Section: Discussionmentioning

confidence: 99%

“…The exchange of tree material may possibly initiate/sustain gene flow between geographically distant pathogen populations, even if the pathogen is incapable of dispersing over long distances (Sakalidis, Feau, Dhillon, & Hamelin, 2016). For Septoria musiva, a pathogen causing stem cankers as well as leaf spot disease (and a close relative of S. populicola), a range expansion was facilitated by human activities (Sakalidis et al, 2016). However, our results do not support this scenario: we neither find evidence of populations that may have acted as sources of colonization, nor do we find pronounced genetic distances between geographically close sites, both of which could be interpreted as signatures of human-assisted colonization (Sakalidis et al, 2016).…”

Section: Discussionmentioning

confidence: 99%

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Supplemental Information 1: Supplemental Information: Figures and Tables

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Understanding the genetic variability and dispersal capabilities of plant pathogens is important to better predict pathogen spread and virulence, especially under global change conditions. The outcome of host-pathogen interactions directly depends on the dispersal capacity of the pathogens, on environmental conditions, and disease resistance of the host. Here, we analysed the distribution of finely resolved phylogenetic lineages of a poplar-specific fungal pathogen (Sphaerulina populicola) in western North America, across a 3,200 km latitudinal gradient of the host tree's (Populus balsamifera) distribution. We specifically tested whether dispersal limitations or environmental filters limit the spread and establishment of the pathogen into new areas. We assessed the genetic diversity of the pathogen with ITS1 oligotypes, recorded by metabarcoding leaf-associated fungal communities. The distribution of the recorded 16 S. populicola oligotypes showed no geographic patterns, indicating the lack of dispersal limitation of the pathogen throughout the investigated area. Climatic conditions also did not seem to restrict the occurrence and abundance of the pathogen oligotypes. Finally, we found strong variation in oligotype presence within single localities, which may suggest the importance of biotic factors in regulating the infection of this well-dispersing fungal pathogen. Our interpretation implies that the future prevalence of S. populicola-related disease will likely depend on the dynamics of host-pathogen interactions, since the pathogen does not seem dispersallimited at a continental scale.

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Genetic patterns reveal historical and contemporary dispersal of a tree pathogen

Cited by 18 publications

References 71 publications

Multiplex qPCR for detection and quantification of Sphaerulina musiva in Populus stems

Multiplex qPCR for detection and quantification of Sphaerulina musiva in Populus stems

Pest categorisation of Sphaerulina musiva

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