Acalypha australis as a Potential Reservoir Host of Hop Stunt Viroid in Vineyards.

Vineyard-associated weeds can serve as reservoirs for grapevine pathogens, but their role in virus and viroid ecology remains unclear. This study aims to examine the presence of grapevine-associated viruses and viroids in symptomatic Acalypha australis plants growing under grapevines in Yeongdong, South Korea. RT-PCR screening conducted on neighboring grapevines revealed mixed infections with multiple viruses and viroids. In A. australis, hop stunt viroid (HSVd), grapevine rupestris stem pitting-associated virus, and grapevine virus E were detected via RT-PCR, with additional support from nanopore sequencing. Sequence and phylogenetic analyses showed that the HSVd isolates from A. australis and grapevine collected from the same vineyard were genetically identical. Mechanical inoculation confirmed HSVd infection in healthy A. australis plants. Additional screening identified HSVd infection in A. australis from Yeongcheon and Haman, and in neighboring grapevines. These findings suggest that A. australis may serve as a potential reservoir host of HSVd in vineyard agroecosystems.