Identification and Characterization of a Novel Efficient Resistance Response to the Furoviruses SBWMV and SBCMV in Barley

The interaction between the furoviruses Soilborne cereal mosaic virus (SBCMV) and Soilborne wheat mosaic virus (SBWMV) and their main host wheat is well documented; however, to date, only a few reports have addressed the response of other cereal species to these viruses. Here, we show that, in contrast to wheat, barley germplasm is a rich source of resistance to furoviruses. Moreover, we demonstrate that barley genotypes respond differentially to SBCMV and SBWMV, thereby providing an additional biological basis for classification of these viruses as two separate species. Following natural (soil) inoculation, some barley genotypes permitted foliar infection by SBWMV, whereas all 22 genotypes tested were resistant to SBCMV. Resistance is unlikely to be directed toward the virus vector, because Polymyxa graminis DNA was detected in the roots of all tested genotypes. Resistance to SBCMV in some barley genotypes was overcome by artificial virus inoculation onto the leaves, suggesting a block on virus translocation from roots to shoots as in resistant wheat genotypes. However, other genotypes were fully resistant following both inoculation techniques. One barley genotype, ‘Dayton,’ exhibited extreme resistance to both furoviruses. Further molecular analyses suggested that this novel and highly efficient resistance to furoviruses in barley operates by limiting virus spread from the primary inoculated cells.