During summer 2022, a cluster of Madagascar periwinkle plants with white and mauve flowers were observed with foliar mild yellow mosaic symptoms on a private property in Harlingen, Cameron County, Texas. The symptoms were reproduced on mechanically inoculated periwinkle and Nicotiana benthamiana plants. Virions of 776 to 849 nm in length and 11.7 to 14.8 nm in width were observed in transmission electron microscopy of leaf dip preparations made from symptomatic periwinkle leaves. Highthroughput sequencing (HTS) analysis of total RNA extracts from symptomatic leaves revealed the occurrence of two highly divergent variants of a novel Potyvirus species as the only virus-like sequences present in the sample. The complete genomes of both variants were independently amplified via RT-PCR, cloned, and Sanger sequenced. The 5' and 3' of the genomes were acquired using RACE methodology. The assembled virus genomes were 9,936 and 9,944 nucleotides (nt) long and they shared 99.9-100% identities with the respective HTS-derived genomes. Each genome encoded hypothetical polyprotein of 3,171 amino acids (aa) (362.6 kDa) and 3,173 aa (362.7 kDa), respectively, and they shared 77.3%/84.4% nt/aa polyproteins identities, indicating that they represent highly divergent variants of the same Potyvirus species. Both genomes also shared below species threshold polyprotein identity levels with the most closely phylogenetically related known potyviruses thus indicating that they belong to a novel species. The name periwinkle mild yellow mosaic virus (PwMYMV) is given to the potyvirus with complete genomes of 9,936 nt for variant 1 (PwMYMV-1) and 9,944 nt for variant 2 (PwMYMV-2). We propose that PwMYMV be assigned into the genus Potyvirus (family Potyviridae).
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