Abstract
Virus yellows is a disease affecting sugar beet that can lead to significant economic losses in Europe. This disease is linked to a complex of three different viruses: Beet yellows virus (BYV), Beet mild yellowing virus (BMYV), and Beet chlorosis virus (BChV). The primary vector for these viruses is the peach-potato aphid, Myzus persicae, which has many host plant species besides sugar beet. However, there is limited information on alternative host plants from agroecosystems for these viruses. This knowledge is crucial because weeds and other plant species that host one or more of the viruses and can overwinter may serve as a virus source in the following year. We investigated whether plant species growing in or near sugar beet fields in Europe can act as host plants for one or more of these viruses. These plants can grow as weeds within sugar beet fields, in flower strips adjacent to fields, or as catch crops preceding the main crop. We selected 22 common plant species and inoculated them with M. persicae carrying a mixture of BYV, BMYV, and BChV. We inoculated 8 plants per species, pooled two plants respectively (resulting in 4 samples per plant species), and checked for the presence and identity of viruses using quantitative reverse transcription polymerase chain reaction (RT-qPCR). Out of the 22 plant species, four were infected with BYV, 17 with BMYV, and three with BChV. Depending on the plant species, one to four out of four samples were infected with one or two viruses. For instance, in Cirsium arvense, an economically significant weed species, we identified BYV in three samples and BMYV in one sample. In Phacelia tanacetifolia, a common species in flower strips and catch crops, we detected BYV in three samples and BMYV in four samples. Among the plant species identified as virus hosts, several can overwinter in mild conditions, such as C. arvense and P. tanacetifolia. Therefore, they can serve as a virus source in the following year. These findings should be considered not only for weed management but also when selecting flower mixtures for flower strips and catch crops as part of agri-environmental schemes in Europe. To clarify the risk of transmission from virus host plants identified in this study to sugar beet, further research is needed to test the re-infection from infested plants back to sugar beet.