Barley Yellow Dwarf Virus Influences Its Vector’s Endosymbionts but Not Its Thermotolerance

Abstract

The barley yellow dwarf virus (BYDV) of cereals is thought to substantially increase the high-temperature tolerance of its aphid vector, Rhopalosiphum padi, which may enhance its transmission efficiency. This is based on experiments with North American strains of BYDV and R. padi. Here, we independently test these by measuring the temperature tolerance, via Critical Thermal Maximum (CTmax) and knockdown time, of Australian R. padi infected with a local BYDV isolate. We further consider the interaction between BYDV transmission, the primary endosymbiont of R. padi (Buchnera aphidicola), and a transinfected secondary endosymbiont (Rickettsiella viridis) which reduces the thermotolerance of other aphid species. We failed to find an increase in tolerance to high temperatures in BYDV-infected aphids or an impact of Rickettsiella on thermotolerance. However, BYDV interacted with R. padi endosymbionts in unexpected ways, suppressing the density of Buchnera and Rickettsiella. BYDV density was also fourfold higher in Rickettsiella-infected aphids. Our findings indicate that BYDV does not necessarily increase the temperature tolerance of the aphid transmission vector to increase its transmission potential, at least for the genotype combinations tested here. The interactions between BYDV and Rickettsiella suggest new ways in which aphid endosymbionts may influence how BYDV spreads, which needs further testing in a field context.

Genetic diversity in vector populations influences the transmission efficiency of an important plant virus

“…Despite the broad effects intra-species diversity (genotype, B. aphidicola strain, facultative endosymbiont presence and strain) has on aphid phenology and behaviour, relatively few studies have examined how these traits impact aphid-virus interactions. Recent studies have started to explore the potential influence facultative endosymbionts might have on the aphid-BYDV relationship [24][25][26]; however, transmission efficiency is often not directly examined [25] or the observed endosymbiont effects cannot be disentangled from the confounding effect of aphid genotype [24]. Genetic variation has been found to underpin transmission efficiency in another aphid-yellow dwarf virus combination [27], but this remains understudied for Rh.…”

Genetic diversity in vector populations influences the transmission efficiency of an important plant virus

“…Despite the broad effects intra-species diversity (genotype, B. aphidicola strain, facultative endosymbiont presence and strain) has on aphid phenology and behaviour relatively few studies have examined how these traits impact aphid-virus interactions. Some recent studies have started to explore the potential influence facultative endosymbionts might have on the aphid-BYDV relationship [24][25][26], however transmission efficiency is often not directly examined [25] or the observed endosymbiont effects cannot be disentangled from the confounding effect of aphid genotype [24]. Genetic variation has been found to underpin transmission efficiency in another aphid-yellow dwarf virus combination [27], but this remains understudied for R. padi, S. avenae, and BYDV-PAV.…”