Impact of vector dispersal and host-plant fidelity on the dissemination of an emerging plant pathogen.

Michael Maixner,Jes Johannesen,Xavier Foissac,Patrik Kehrli

doi:10.1371/journal.pone.0051809

Michael Maixner, Jes Johannesen + Show 2 more

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https://doi.org/10.1371/journal.pone.0051809

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Abstract

Dissemination of vector-transmitted pathogens depend on the survival and dispersal of the vector and the vector's ability to transmit the pathogen, while the host range of vector and pathogen determine the breath of transmission possibilities. In this study, we address how the interaction between dispersal and plant fidelities of a pathogen (stolbur phytoplasma tuf-a) and its vector (Hyalesthes obsoletus: Cixiidae) affect the emergence of the pathogen. Using genetic markers, we analysed the geographic origin and range expansion of both organisms in Western Europe and, specifically, whether the pathogen's dissemination in the northern range is caused by resident vectors widening their host-plant use from field bindweed to stinging nettle, and subsequent host specialisation. We found evidence for common origins of pathogen and vector south of the European Alps. Genetic patterns in vector populations show signals of secondary range expansion in Western Europe leading to dissemination of tuf-a pathogens, which might be newly acquired and of hybrid origin. Hence, the emergence of stolbur tuf-a in the northern range was explained by secondary immigration of vectors carrying stinging nettle-specialised tuf-a, not by widening the host-plant spectrum of resident vectors with pathogen transmission from field bindweed to stinging nettle nor by primary co-migration from the resident vector's historical area of origin. The introduction of tuf-a to stinging nettle in the northern range was therefore independent of vector's host-plant specialisation but the rapid pathogen dissemination depended on the vector's host shift, whereas the general dissemination elsewhere was linked to plant specialisation of the pathogen but not of the vector.

Highlights

The emergence of vector-transmitted plant symbionts/pathogens depends highly on vector dispersal and the host specificity of vector and pathogen [1]
H. obsoletus was analysed for mtDNA sequences NADH dehydrogenase subunit I (400 bp), Cytochrome Oxidase subunit I (CO I) (198 bp), tRNA(Leu) (67 bp) and Cytochrome Oxidase subunit II (CO II) (523 bp), using the primers and protocol in [32]
We investigated the origin and population history of an emerging insect-vectored plant pathogen by considering how vector dispersal and plant fidelity of both the pathogen and the vector interact on the dissemination process

Summary

Introduction

The emergence of vector-transmitted plant symbionts/pathogens depends highly on vector dispersal and the host specificity of vector and pathogen [1]. This indicates that vector populations using stinging nettle in this area originated from local bindweed populations and that two genetic host-race populations have evolved perhaps since the host shift over the past 25 years (Fig. 1a,b). The parallel associations among stolbur strains, vector populations and host plants in Germany and Alsace imply two independent vector transmission cycles of stolbur phytoplasma, one associated with stinging nettle as a new plant host and one associated predominately with field bindweed and involving other host plants [16]. In this case, monophyly of stolbur infecting field bindweed to stinging nettle in the geographic region of the host shift relative to regions outside is expected. The vector’s host-shift is independent of stolbur infection but essential for the dissemination in a new environment

Materials and Methods

Results

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Discussion