Interactions Within Susceptible Hosts Drive Establishment of Genetically Distinct Variants of an Insect-Borne Pathogen

Abstract

Coinfections are common, leading to pathogen interactions during transmission and establishment in a host. However, few studies have tested the relative strengths of pathogen interactions in vectors and hosts that determine the outcome of infection. We tested interactions between two genetically distinct variants of the mealybug-transmitted Grapevine leafroll-associated virus 3. The transmission efficiency of each variant in single variant inoculations by two vector species was determined. The effects of vector species, a coinfected source, and simultaneous inoculation from multiple hosts to one host on variant establishment were examined. Within-vector interactions could have a role in transmission from hosts containing mixed infections, but not when vectors were moved from separate singly infected source plants to a single recipient plant. The invasive Planococcus ficus (Signoret) was a more efficient vector than Pseudococcus viburni (Signoret). Transmission efficiency of the two variants did not differ in single variant inoculations. Overall infections were the same whether from singly or coinfected source plants. In mixed inoculations, establishment of one variant was reduced. Mixed inoculations from two singly infected source plants resulted in fewer mixed infections than expected by chance. Therefore, the observed outcome was determined subsequent to host inoculation rather than in the vector. The outcome may be due to resource competition between pathogens. Alternatively apparent competition may be responsible; the pathogens' differential ability to overcome host defenses and colonize the host may determine the final outcome of new infections. Detailed knowledge of interactions between pathogens during transmission and establishment could improve understanding and management of disease spread.

Disease progression of vector-mediated Grapevine leafroll-associated virus 3 infection of mature plants under commercial vineyard conditions

“…While our findings are informative, similar studies should be performed with other mealybug species, genetically distinct variants of GLRaV-3, grape cultivars, and in different climatic conditions to evaluate the general applicability of the results (Bahder et al 2013;Blaisdell et al 2015;Salem-Fnayou et al 2006). For example, berry quality of white wine varieties is affected by GLRaV-3 infection, yet resulting disease symptoms are not readily identifiable (Kovacs et al 2001).…”

“…Furthermore, Pl. ficus is a known vector of GLRaV-3 (Blaisdell et al 2015;Engelbrecht and Kasdorf 1990). Field cuttings were collected on 4 October 2012 and the stem bases were placed in flasks of water.…”

Viral Diversity in Autochthonous Croatian Grapevine Cultivars

“…To identify GLRaV-3 specific variants the Qiagen One-Step RT-PCR kit was used following the protocols with fluorescently labeled primers as described by Sharma et al (2011) for group I, II, III, and IV, and Blaisdell et al (2015) for group VI. For other variants that may not be identified by the above-mentioned primers, a coat protein (CP) primer set was used (Sharma et al 2011).…”

Ferrisia gilli(Hemiptera: Pseudococcidae) Transmits Grapevine Leafroll-Associated Viruses

“…Therefore, all mealybugs colonizing grapevines should be considered as potential vectors of GLRaV. However, transmission efficiency can differ greatly among mealybug species (e.g., Blaisdell et al 2015).…”