Viruses in natural populations of wild hop in the south of Western Siberia

Wild hops are abundant in the southern regions of Western Siberia, Russia, where the natural conditions are favorable for growing commercially valuable varieties. The genetic diversity present in wild hop populations serves as a valuable source of beneficial genes for developing new genotypes. However, before harnessing these traits, it's crucial to test the wild hops for the presence of harmful phytopathogenic viruses, which tend to accumulate in natural repositories. This study aimed to evaluate the prevalence of viral and viroid infections in wild hop populations in the Altai Territory and the Altai Republic. Plant material from wild hops (Humulus lupulus L. 1753) was collected during expeditions from July 15 to August 15 in both 2022 and 2023, covering 18 districts. Using DAS-ELISA and real-time RT-PCR, we assessed 243 samples for the presence of 16 viruses and 1 viroid. The frequency of infected plants varied based on the sampling location and the specific pathogen. Notably, three particularly damaging hop viruses – Hop latent virus (HpLV), Apple mosaic virus (ApMV), and Arabis mosaic virus (ArMV) – were identified, infecting 24.5%, 8.2%, and 5.5% of the studied plants, respectively. HpLV was found throughout the region, primarily in the moderate-arid steppe and forest-steppe, while ApMV was detected in three adjacent districts with a frequency ranging from 11.2% to 45.5%. ArMV was found in half of the plants in a single location. Additionally, minor viruses such as Strawberry latent ringspot (SLRSV), Tobacco necrosis virus (TNV), and Tobacco ringspot virus (TRSV) appeared sporadically in different zones. Potato mosaic viruses S and Y, as well as Potato leafroll virus (PLRV), were widely distributed in wild hop populations, with high frequencies in all natural zones except the foothills. Potato viruses M (PVM), Potato viruses A (PVA), and Potato viruses X (PVX) were common in the steppe and forest-steppe zones. It's important to note that the presence of viral infection in plants did not necessarily correlate with the expression of disease symptoms. Notably, Hop mosaic virus (HpMV), Petunia asteroid mosaic virus (PetAMV), Prunus necrotic ringspot virus (PNRSV), and Potato spindle tuber viroid (PSTVd) were not detected. The existence of natural reservoirs of viral infection poses a threat to commercial hop cultivars in areas where they coexist. As such, it is imperative to monitor and control the spread of these dangerous viruses.