Populus genotypes differ in infection by, and systemic spread of, Poplar mosaic virus

Abstract

The spatial and temporal dynamics of Poplar mosaic virus (PopMV) infection were investigated using four different genotypes of Populus . Four Populus clones were vegetatively propagated under sterile conditions and used as hosts for PopMV infection in controlled growth-room experiments. The presence of PopMV RNA was assessed using reverse transcriptase PCR. The presence of infectious PopMV particles was assessed by the ability of extracts from Populus leaves to generate PopMV symptoms on the propagation host, Nicotiana megalosiphon . Neither PopMV RNA nor infectious particles accumulated to detectable levels in one of the four clones (CT6009), suggesting that this clone had preformed resistance to PopMV. PopMV RNA and infectious particles were restricted to the inoculated leaf in two of the clones (AP37 and NM6), suggesting that these clones restricted either the rate of virus accumulation or the spread of PopMV itself. In contrast, PopMV systemically infected one clone (52-226), indicating that this host was either fully susceptible, or had delayed resistance.

Genotype and time of day shape the Populus drought response

“…Trees of the genus Populus have highly variable and genotype‐specific responses to a variety of environmental stimuli. For example, hybrid poplar clones display a broad range of within‐genus susceptibility to the pathogen poplar mosaic virus (Smith and Campbell, 2004). Similarly, exposure to elevated carbon dioxide and ozone induces significant clone‐specific responses (Oksanen et al.…”

The response of the poplar transcriptome to wounding and subsequent infection by a viral pathogen

“…The experimental material was collected at single time-point that ensured that the inoculated leaves were completely PopMV-infected, but at a time that was likely beyond that which would document only a wound response. Previous studies had determined that inoculated clones of Populus hybrid 52-226 were definitely PopMV infected by 14 dpi (Smith & Campbell, 2004b), so this was chosen as the time-point for these experiments. It is possible that this time-point was beyond that which documents the maximum changes in transcript abundance in response to PopMV; however, it may allow a better discrimination of PopMV-mediated effects from those induced by wounding.…”

“…The natural vector for transmission of PopMV is not known, although it is clear that the virus can be readily transmitted after wounding, allowing the virus to spread if plants are propagated by cuttings (Biddle & Tinsley, 1971c). PopMV was reported to induce chlorosis of the leaves of infected Populus (Biddle & Tinsley, 1971a; Atkinson & Cooper, 1976) but recent analyses suggest that this symptom is not necessarily diagnostic for the presence of the virus (Smith & Campbell, 2004b). Little is known about the long‐term effects of PopMV on Populus growth and development, but a reduction in the growth of several nursery cultivars has been documented (Biddle & Tinsley, 1971c).…”

“…Little is known about the long‐term effects of PopMV on Populus growth and development, but a reduction in the growth of several nursery cultivars has been documented (Biddle & Tinsley, 1971c). There is growing evidence to suggest that spread of PopMV within infected Populus hosts is contingent on the genotype of the host (Cooper & Edwards, 1981; von Kontzog & Ebrahim‐Nesbat, 1992) (Smith & Campbell, 2004b), but the basis for this is not yet known. To date, the molecular responses that are invoked in Populus following PopMV infection remain to be documented.…”

“…As a first step in characterizing the molecular responses of Populus to PopMV, we examined alterations in the activity of the Populus transcriptome following PopMV infection. Making use of a compatible Populus –PopMV pathosystem that was recently shown to permit systemic spread of the virus by 14 d post inoculation (Smith & Campbell, 2004b), we characterized the changes in the host transcript accumulation using spotted cDNA microarrays. Here we show that relatively modest, but highly reproducible changes in transcriptome activity are invoked by wounding and PopMV infection.…”