RESISTANCE TO RPV BARLEY YELLOW DWARF VIRUS IN THE GENUS BROMUS

Susceptibility to barley yellow dwarf RPV (BYD-RPV) relative to BYD-PAV has been studied for 21 species of the genus Bromus. The following species belonging to sections Bromus (B. arvensis L., B. commutatus Shrad, B. danthoniae Trin., B. grossus Desf. ex DC., B. hordeaceus L., B. lanceolatus Roth., B. scoparius L.), Stenobromus (B. diandrus Roth., B. madritensis L., B. sterilis L., B. rubens L., B. tectorum L.), and Neobromus (B. trinii Desvaux) are all susceptible to BYD-RPV. Of the three species of the Pnigma section, B. erectus Hudson is susceptible to BYD-RPV, although the percentage of infected plants is low; B. setifolius Presl. is resistant to BYD-RPV; and the two biotypes of B. inermis Leyss. that were tested are both resistant to BYD-RPV. Most biotypes of the species in section Ceratochloa are resistant to BYD-RPV and susceptible to BYD-PAV. In B. catharticus Vahl. a few biotypes are also susceptible to both viruses. The resistance to BYD-RPV in different biotypes of Ceratochloa and in one biotype of B. setifolius cannot be explained by the resistance to the vector Rhopalosiphum padi L., as BYD-PAV is efficiently transmitted to these biotypes by the same aphid species. These results show that most biotypes of the species in section Ceratochloa are probably immune to BYD-RPV and that the virus has a restricted host range in the genus Bromus compared with BYD-PAV.