The Virome of Rhubarb Consists of Diverse Viruses Belonging to at Least Four Families.

Abstract

Culinary rhubarb (Rheum spp.) comprises herbaceous perennials that are primarily clonally propagated. Like other asexually reproduced crops, rhubarb is vulnerable to virus transmission, but its virome remains poorly characterized. In April 2024, foliar virus-like symptoms including chlorotic and necrotic leaf spots, chlorosis, and stunting were observed on cultivar 'Kerwin' in the rhubarb collection at Cornell AgriTech in Geneva, NY. Symptomatic leaf tissue tested positive for tomato ringspot virus (ToRSV) in double antibody sandwich enzyme-linked immunosorbent assay using specific antibodies. Subsequently, the virome of 40 rhubarb entries was determined using high-throughput sequencing (HTS) and bioinformatic analyses. Sequence information suggested the presence of ToRSV (genus Nepovirus, family Secoviridae), cherry leafroll virus (CLRV, genus Nepovirus, family Secoviridae), Arabis mosaic virus (ArMV, genus Nepovirus, family Secoviridae), broad-leafed dock virus A (BLDVA, genus Macluravirus, family Potyviridae), tobacco streak virus (TSV, genus Ilarvirus, family Bromoviridae), and beet curly top virus (BCTV, genus Curtovirus, family Geminiviridae) in composite leaf samples. The occurrence of these RNA and DNA viruses was confirmed in composite and individual samples after deconvolution by RT-PCR or PCR, respectively, using one or two primer pairs, in combination with bidirectional Sanger sequencing of the amplicons. The symptoms of cultivar 'Kerwin' could not be definitively assigned to ToRSV due to co-infection with BLDVA. This is the first characterization of the rhubarb virome by HTS and the first report of ToRSV, BLDVA, TSV and BCTV in culinary rhubarb. These findings have implications for the propagation of clean material, distribution of germplasm, and future breeding efforts in rhubarb.