Biology

AsMaV is a typical member of the emaravirus genus affecting Eurasian aspen and widespread in Fennoscandia. The virus has been confirmed as the causal agent of the mosaic disease of aspen (Rehanek et al. 2022) which is characterized by distinct leaf symptoms such as mosaic, mottle, yellow blotching, variegation, and chloroses along veins. The mosaic disease of aspen has been shown to be graft-transmissible in Populus tremula (von Bargen et al. 2020). AsMaV was confirmed as causal agent of the disease by detection of AsMaV using virus-specific RT-PCR in grafted scions and symptomatic rootstocks, in combination with HTS analyses, showing that AsMaV was the only virus detectable in the infected scions and rootstocks. Mechanical transmission to a set of herbaceous indicator plants failed to establish a stable AsMaV infection in Nicotiana benthamiana, N. tabacum cv. samsun, N. clevelandii, Cucumis sativus, Chenopodium quinoa, C. amaranticolor or Phaseolus vulgaris. However, the virus was detectable by virus-specific RT-PCR in P. vulgaris and N. benthamiana, that were directly rub inoculated with plant sap from P. tremula. Despite this, no symptoms were induced, and propagation to new indicator plants of the same species was unsuccessful. As other emaraviruses, AsMaV is considered to be naturally dispersed by eriophyoid mites. Although several mite species were found to infest mosaic-diseased aspen (Phyllocoptes populi, Eriophyes diversipunctatus), the vector has not been identified until now (von Bargen et al. 2020).

AsMaV-infected leaves of Eurasian aspen (P. tremula) showing vein yellowing (left) and yellow blotching (right)