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Potato aucuba mosaic virus (PAMV), a positive single-strand RNA virus, has one of the longest genomes of the viruses in the genus Potexvirus. In 2019, potato samples with mottle and crinkling symptoms from Huzhou, Zhejiang province, China, were identified to be infected with PAMV, potato virus X (PVX), and potato virus Y (PVY) by transcriptome sequencing. To study the effects of single infection by PAMV, the full-length sequence of PAMV from Huzhou (MT193476) was determined and an infectious full-length cDNA clone was constructed. This cDNA clone was infectious by agro-infiltration, leading to systemic symptoms in Nicotiana benthamiana, tomato, pepper, and potato.

In this report, the full genome sequence of a novel mycovirus, designated as "Rhizoctonia solani partitivirus SM03" (RsPV-SM03), was determined in Rhizoctonia solani AG-4 HG III isolate SM03. RsPV-SM03 genome consists of two dsRNAs (dsRNA-1 and dsRNA-2), each of them contains one single open reading frame (ORF). ORF1 of dsRNA-1 encodes a putative RNA-dependent RNA polymerase (RdRp), while ORF2 of dsRNA-2 encodes a putative viral coat protein (CP). Phylogenetic analysis indicated that the RdRp and CP of RsPV-SM03 are closely related to those of other members of the genus Alphapartitivirus, family Partitiviridae, suggesting that RsPV-SM03 represents a novel species in the genus Alphapartitivirus.

The complete nucleotide sequence of a novel mycovirus, designated as "Rhizoctonia fumigata bipartite virus 1" (RfBV1), from Rhizoctonia fumigata AG-Ba isolate C-314 Baishi was determined. The genome of RfBV1 is composed of two double-stranded RNAs (dsRNA). dsRNA-1 (2311 bp) contains one open reading frame (ORF), which codes for the putative RNA-dependent RNA polymerase (RdRp) of the virus. dsRNA-2 (1690 bp) contains one ORF, which encodes a putative protein whose function is unknown. Phylogenetic analysis indicated that the RdRp of RfBV1 clustered with several unassigned bipartite viruses belonging to the CThTV-like viruses group, but not the family Amalgaviridae or Partitiviridae. Our study suggests that RfBV1 is a novel mycovirus related to the CThTV-like viruses.

Tombusvirus-like associated RNAs (tlaRNAs) are positive-sense single-stranded RNAs found in plants co-infected with some viruses of the genus Polerovirus. Pod pepper vein yellows virus (PoPeVYV) was recently reported as a new recombinant polerovirus causing interveinal yellowing, stunting, and leaf rolling in Capsicum frutescens plants at Wenshan city, Yunnan province, China. The complete genome sequence of its associated RNA has now been determined by next-generation sequencing and reverse transcription (RT) polymerase chain reaction (PCR). PoPeVYV-associated RNA (PoPeVYVaRNA) (GenBank Accession No. MW323470) has 2970 nucleotides and is closely related to other group II tlaRNAs, particularly tobacco bushy top disease-associated RNA (TBTDaRNA, GenBank Accession No. EF529625). In infection experiments on Nicotiana benthamiana and C. frutescens plants, synergism between PoPeVYVaRNA and PoPeVYV was demonstrated, leading to severe interveinal yellowing of leaves and stunting of plants. The results provide further information on the genetic and biological properties of the various agents associated with pepper vein yellows disease (PeVYD).

Pepper vein yellows viruses (PeVYV) are phloem-restricted viruses in the genus Polerovirus, family Luteoviridae. Typical viral symptoms of PeVYV including interveinal yellowing of leaves and upward leaf curling were observed in pod pepper plants (Capsicum frutescens) growing in Wenshan city, Yunnan province, China. The complete genome sequence of a virus from a sample of these plants was determined by next-generation sequencing and RT-PCR. Pod pepper vein yellows virus (PoPeVYV) (MT188667) has a genome of 6015 nucleotides, and the characteristic genome organization of a member of the genus Polerovirus. In the 5’ half of its genome (encoding P0 to P4), PoPeVYV is most similar (93.1% nt identity) to PeVYV-3 (Pepper vein yellows virus 3) (KP326573) but diverges greatly in the 3’-part encoding P5, where it is most similar (91.7% nt identity) to tobacco vein distorting virus (TVDV, EF529624) suggesting a recombinant origin. Recombination analysis predicted a single recombination event affecting nucleotide positions 4126 to 5192 nt, with PeVYV-3 as the major parent but with the region 4126-5192 nt derived from TVDV as the minor parent. A full-length clone of PoPeVYV was constructed and shown to be infectious in C. frutescens by RT-PCR and the presence of icosahedral viral particles.

Tombusvirus-like associated RNAs (tlaRNAs) are positive-sense single-stranded RNAs found in plants co-infected with viruses of the genus Polerovirus. TlaRNAs depend upon capsid proteins supplied in trans by the co-infecting polerovirus vector for transmission and intra-host systemic movement. Here, the full-length genomes of five tlaRNAs were determined using a combination of RT-PCR and next-generation sequencing, and evidence is provided for an additional tlaRNA associated with potato leafroll virus. Phylogenetic analyses based on conserved domains of the RdRp placed tlaRNAs as a monophyletic clade clustering with members of the family Tombusviridae and comprising three different subclades. Full-length clones of tlaRNAs from two of three subclades were confirmed to replicate autonomously, and each produces a subgenomic RNA during infection.