Series of resistance genes in barley (Hordeum vulgare L.) that control Barley yellow mosaic virus multiplication and the root-to-leaf systemic movement.

The infection of young winter barley (Hordeum vulgare L.) root system in winter by Barley yellow mosaic virus (BaYMV) can lead to high yield losses. Resistance breeding is critical for managing this virus, but there are only a few reports on resistance genes that describe how the genes control BaYMV propagation and the systemic movement from the roots to the leaves. Here we report a real-time quantitative PCR analysis of the virus in barley roots and leaves carrying BaYMV resistance genes (rym1-rym15 and an unknown gene) to elucidate the molecular mechanisms underlying the barley response to BaYMV. The resistance mechanism directly targets the virus. Moreover, the resistance genes/cultivars were classified into the following three groups according to their BaYMV titer: (1) immune (BaYMV was undetectable in the roots or leaves); (2) partially immune (BaYMV was detected in the roots, but not in the leaves); (3) susceptible (BaYMV was detected in the roots and leaves). Our results clarified the functions of the resistance genes in barley roots and leaves following a BaYMV infection. We anticipate our analysis to be a starting point for more understanding the correspondence between resistance genes of Triticeae and the soil-borne viruses.