Psammotettix alienus-mediated inoculations of barley and wheat strains of Wheat dwarf virus to wild gramineous species

Wheat dwarf virus (WDV, family Geminiviridae, genus Mastrevirus) is the causal agent of dwarfing, mottling and yellowing symptoms in wheat and barley. WDV is exclusively transmitted by leafhoppers from the genus Psammotettix in a persistent manner and infects plants of the Poaceae family. Phylogenetic analyses carried out with WDV genomic sequences showed that this viral species comprises several strains including the originally described wheat (WDV-w) and barley (WDV-b) strains. Psammotettix leafhoppers collected in different French cereal-growing areas were characterized using recordings of vibrational signals used during mating, morphometric analyses and sequences of the COI gene. Characterized P. alienus individuals were used as WDV vectors to assess the host ranges of isolates from the WDV-w and WDV-b strains. Thirty-seven wild gramineous species were identified in a 5-km² cereal-growing area located in Annoix (Cher, France) where WDV and Psammotettix leafhoppers are usually highly prevalent (Gauthier et al., 2017). Whenever seeds were available, susceptibility of wild gramineous species to WDV was tested using P. alienus-mediated WDV inoculations. The characterization of field-collected Psammotettix showed that P. alienus is the prevalent Psammotettix species and sometimes it is found syntopically with P. confinis. Leafhopper mediated transmission experiments highlighted that (i) the two WDV strains have different but slightly overlapping host ranges, (ii) three gramineous species not yet reported to be WDV hosts (i.e. Alopecurus myosuroides, Cynosurus cristatus and Poa annua) could be infected by WDV, and (iii) Setaria viridis, described in the literature as non-host for WDV, was successfully infected by the WDV-w isolate.