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One large contig with high sequence similarity to Asian prunus virus 2 was identified by high-throughput sequencing from a camellia (Camellia japonica) tree with ringspot symptoms. The complete genome of this new virus was determined to be 8829 nucleotides long, excluding the 3′ poly(A) tail. Its genome organization resembles that of known foveaviruses but contains an additional open reading frame in the 3′-terminal region. Phylogenetic analysis also places this virus with members of the genus Foveavirus in the family Betaflexiviridae in the same subgroup. The virus, which is provisionally named \"camellia ringspot-associated virus 4″, shares 50–56% nucleotide sequence identity with other foveaviruses and should represent a new species in the genus.

Asymmetric sequential hydrogenations of α‐methylene γ‐ or δ‐keto carboxylic acids are established in one‐pot using a bimetallic Ru/Ru catalyst system, achieving the stereodivergent synthesis of all four stereoisomers of both chiral γ‐ and δ‐lactones with two non‐vicinal carbon stereocenters in high yields (up to 99%) and with excellent stereoselectivities (up to >99% ee and >20:1 dr). The compatibility of the two chiral Ru catalyst systems is investigated in detail, and it is found that the basicity of the reaction system plays a key role in the sequential hydrogenation processes. The protocol can be performed on a gram‐scale with a low catalyst loading (up to 11000 S/C) and the resulting products allow for many transformations, particularly for the synthesis of several key intermediates useful for the preparation of chiral drugs and natural products. Asymmetric sequential hydrogenations of α‐methylene γ‐ or δ‐keto carboxylic acids are established in one‐pot using a bimetallic Ru/Ru catalyst system, achieving the stereodivergent synthesis of all four stereoisomers of both chiral γ‐ and δ‐lactones in high yields (up to 99%) and with excellent stereoselectivities (up to >99% ee and >20:1 dr).

An emerging virus-like flower yellowing disease (FYD) of green Sichuan pepper (Zanthoxylum armatum v. novemfolius) has been recently reported. Four new RNA viruses were discovered in the FYD-affected plant by the virome analysis using high-throughput sequencing of transcriptome and small RNAs. The complete genomes were determined, and based on the sequence and phylogenetic analysis, they are considered to be new members of the genera Nepovirus (Secoviridae), Idaeovirus (unassigned), Enamovirus (Luteoviridae), and Nucleorhabdovirus (Rhabdoviridae), respectively. Therefore, the tentative names corresponding to these viruses are green Sichuan pepper-nepovirus (GSPNeV), -idaeovirus (GSPIV), -enamovirus (GSPEV), and -nucleorhabdovirus (GSPNuV). The viral population analysis showed that GSPNeV and GSPIV were dominant in the virome. The small RNA profiles of these viruses are in accordance with the typical virus-plant interaction model for Arabidopsis thaliana. Rapid and sensitive RT-PCR assays were developed for viral detection, and used to access the geographical distributions. The results revealed a correlation between GSPNeV and the FYD. The viruses pose potential threats to the normal production of green Sichuan pepper in the affected areas due to their natural transmission and wide spread in fields. Collectively, our results provide useful information regarding taxonomy, transmission and pathogenicity of the viruses as well as management of the FYD.

A new badnavirus was identified in an ornamental camellia tree with yellow mottle symptom. The complete circular double-stranded DNA genome of this virus was found to consist of 8,203 bp. Its genome organization is typical of badnaviruses, containing three open reading frames (ORFs). ORFs 1 and 2 encode putative proteins with unknown functions. ORF3 encodes a large polyprotein that contains almost all of the conserved domains of badnaviruses. The virus shares 55-62% nucleotide sequence identities with other badnaviruses in the RT+RNase H region. Phylogenetic analyses placed it in group I of the genus Badnavirus. Therefore, this virus, which is tentatively named “camellia Lemon Glow virus”, should represent a new species of the genus Badnavirus. This virus was found to be present in approximately a quarter of camellia trees tested.

A new virus with sequence similarities to members of the genus Cavemovirus in the family Caulimoviridae was identified in an Epiphyllum hybrid. The complete genome of the virus, tentatively named “epiphyllum virus 4” (EpV-4), was determined to be 7,296 nucleotides long. Its circular genome organization is typical of cavemoviruses, containing four open reading frames. This virus and the two known cavemoviruses share 67-69% and 72-75% overall nucleotide sequence identity in the replicase gene. Phylogenetic analysis placed EpV-4 in a same cluster with the two recognized cavemoviruses. Thus, EpV-4 should be considered a representative of a third species of the genus Cavemovirus. The virus was transmitted by grafting.

A novel positive-stranded RNA virus provisionally named \"citrus virus C\" (CVC) was discovered in citrus trees displaying mottling symptoms. Its genome comprises 7,215 nucleotides (nt), excluding the 3’ poly(A) tail, and contains two open reading frames (ORFs) that encode a replication-associated polyprotein (RP) and a putative coat protein (CP). The CVC genome contains a 16-nt ‘marafibox’, which is highly conserved in most viruses belonging to the genus Marafivirus of the same family. Sequence analysis suggested that the virus is most closely related to grapevine Red Globe virus (GRGV), which is yet to be officially classified in the family Tymoviridae. The sequence identities between CVC and GRGV in the whole genome (50.7%, nt) and CP (49.4% for amino acid, and 53.9% for nt) are lower than the thresholds (80% in the genome and 90% in the CP) for species demarcation in the family. Therefore, it is legitimate to propose that CVC is a member of new species in the family Tymoviridae.

Contigs with the highest sequence similarity (73%) to Apricot pseudo-chlorotic leaf spot virus (genus Trichovirus, family Betaflexiviridae) were identified by high-throughput sequencing from a symptomless sweet cherry accession. The complete genome sequence of this new virus is 7460 nucleotides, excluding the 3′ poly(A) tail. Its genome organization is very similar to several trichoviruses infecting fruit trees, with three open reading frames encoding putative replicase, movement protein and coat protein (CP). The virus shares amino acid sequence identities of 60–73% at replicase and 53–76% at CP with other trichoviruses. Phylogenetic analyses group it and other trichoviruses in a cluster. These results support that this virus, which is tentatively named cherry latent virus 1, should be considered a new member in the genus Trichovirus.

Chinese bayberry (Myrica rubra) is an economically significant fruit tree native to eastern Asia and widely planted in south-central China. However, studies about the viruses infecting M. rubra remain largely lacking. In the present study, we employed the metatranscriptomic method to identify viruses in M. rubra leaves exhibiting yellowing and irregular margin symptoms collected in Fuzhou, a city located in China’s Fujian province in the year 2022. As a consequence, a novel member of the genus Totivirus was identified and tentatively named “Myrica rubra associated totivirus 1” (MRaTV1). The genome sequencing of MRaTV1 was determined by overlapping reverse transcription polymerase chain reaction (RT-PCR) and rapid amplification of cDNA ends (RACE). The two deduced proteins encoded by MRaTV1 have the highest amino acid (aa) sequence identity to the coat protein (CP) and RNA-dependent RNA polymerase (RdRP) of Panax notoginseng virus A (PNVA), a member of the genus Totivirus within the family Totiviridae, at 49.7% and 61.7%, respectively. According to the results of the phylogenetic tree and the species demarcation criteria of the International Committee on Taxonomy of Viruses (ICTV) for the genus Totivirus, MRaTV1 is considered a new member of the genus Totivirus.

Citrus tristeza virus (CTV) is one of the most important citrus viruses in the world. In this study, we established a reverse-transcription droplet digital polymerase chain reaction (RT-ddPCR) method for the sensitive and accurate quantification of CTV. Quantitative linearity, sensitivity and accuracy of RT-ddPCR were compared to those of reverse-transcription real time PCR (RT-qPCR) by using 10-fold serial dilutions of the CTV RNA transcripts. Both methods showed a high degree of linearity (R2 = 0.991) and quantitative correlation, although RT-ddPCR revealed 100-fold higher sensitivity than RT-qPCR. The detection results for heat-treatment citrus samples also showed that the positive detection rate of RT-ddPCR (73.2%) was higher than that of RT-qPCR (53.6%). In summary, the results indicated that RT-ddPCR may contribute to improved analytical sensitivity and accuracy for CTV detection.

Background ‘Rapid Apple Decline’ (RAD) is a newly emerging problem of young, dwarf apple trees in the Northeastern USA. The affected trees show trunk necrosis, cracking and canker before collapse in summer. In this study, we discovered and characterized a new luteovirus from apple trees in RAD-affected orchards using high-throughput sequencing (HTS) technology and subsequent Sanger sequencing. Methods Illumina NextSeq sequencing was applied to total RNAs prepared from three diseased apple trees. Sequence reads were de novo assembled, and contigs were annotated by BLASTx. RT-PCR and 5′/3’ RACE sequencing were used to obtain the complete genome of a new virus. RT-PCR was used to detect the virus. Results Three common apple viruses and a new luteovirus were identified from the diseased trees by HTS and RT-PCR. Sequence analyses of the complete genome of the new virus show that it is a new species of the genus Luteovirus in the family Luteoviridae . The virus is graft transmissible and detected by RT-PCR in apple trees in a couple of orchards. Conclusions A new luteovirus and/or three known viruses were found to be associated with RAD. Molecular characterization of the new luteovirus provides important information for further investigation of its distribution and etiological role.