Impact of Vector Dispersal and Host-Plant Fidelity on the Dissemination of an Emerging Plant Pathogen

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.

The molecular epidemiology of bois noir grapevine yellows caused by ‘Candidatus Phytoplasma solani’ in the Republic of Macedonia

“…East and causes serious economic losses in grapevine production (Johannesen et al 2012;Aryan et al 2014;Cvrković et al 2014).…”

“…In the case of BN, grapevines are an erroneous food substrate for H. obsoletus and, consequently, a dead-end host for 'Ca. P. solani' (Johannesen et al 2012). The epidemiology of BN is coupled to the infection of herbaceous host plants, which are the primary food sources for H. obsoletus nymphs and pathogen reservoirs.…”

“…P. solani' consists of two genetically divergent strain types, tuf-a and tuf-b, which are involved in the two diverse epidemiological cycles of BN (Langer and Maixner 2004). The tuf-b type is primarily associated with field bindweed (Convolvulus arvensis), the major host plant of H. obsoletus in the eastern and southeastern occurrences of the disease (Langer and Maixner 2004;Johannesen et al 2012), although it infects a number of diverse weedy plants ( Riedle-Bauer et al 2008;Johannesen et al 2012;Cvrković et al 2014). Tuf-a strains of 'Ca.…”

“…Phytoplasma solani' are spread via an epidemic cycle sourced in stinging nettle (Urtica dioica) which is the only documented herbaceous reservoir of this 'Ca. P. solani' genotype (Langer and Maixner 2004;Johannesen et al 2012). The nettlesourced epidemiological cycle is the most common in the northwestern disease range (Germany, Switzerland and northern France), and it was recently registered as the cause of an epidemic BN outbreak in Austria (Aryan et al 2014).…”

“…Phytoplasma solani' through a multilocus sequencing approach (Cimerman et al 2009;Fabre et al 2011;Pacifico et al 2009). These two genes have higher sequence variability than the tuf gene, and thus they are more widely used in epidemiological studies of BN phytoplasmas (Johannesen et al 2012;Aryan et al 2014;Cvrković et al 2014;Kostadinovska et al 2014).…”