Hop Latent Viroid: A Hidden Threat to the Cannabis Industry.

Hop latent viroid (HLVd) is the biggest concern for cannabis and hop growers worldwide. Although most HLVd-infected plants remain asymptomatic, research on hops has demonstrated a decrease in both the α-bitter acid and terpene content of hop cones, which affects their economic value. The HLVd-associated "dudding" or "duds" disease of cannabis was first reported in 2019 in California. Since then, the disease has become widespread in cannabis-growing facilities across North America. Although severe yield loss associated with duds disease has been recorded, little scientific information is available to growers in order to contain HLVd. Consequently, this review aims to summarise all of the scientific information available on HLVd so as to be able to understand the effect of HLVd on yield loss, cannabinoid content, terpene profile, disease management and inform crop protection strategies.

Occurrence and distribution of viruses infecting potato in Russia.

Potato viral disease has been a major problem in potato production worldwide including Russia. Here, we detected Potato Virus M (PVM), P (PVP), S (PVS), Y (PVY), and X (PVX) and Potato Leaf Roll Virus (PLRV) by RT-PCR on potato leaves and tubers from the Northwestern (NW), Volga (VF), and Far Eastern (FE) federal districts of Russia. Each sample was co-infected with up to five viruses. RT-PCR disclosed all six viruses in NW, three in VF, and five in FE. Phylogenetic analyses of PVM and PVS strains resolved all PVM isolates in Group O (ordinary) and all PVS isolates in Group O. Seven PVY strains were detected, and they included only recombinants. PVY recombinants were thus the dominant potato virus strains in Russia, although they widely varied among the regions. Our research provides insights into the geographical distribution and genetic variability of potato viruses in Russia.

Analysis of Synonymous Codon Usage Bias in Potato Virus M and Its Adaption to Hosts.

Potato virus M (PVM) is a member of the genus Carlavirus of the family Betaflexviridae and causes large economic losses of nightshade crops. Several previous studies have elucidated the population structure, evolutionary timescale and adaptive evolution of PVM. However, the synonymous codon usage pattern of PVM remains unclear. In this study, we performed comprehensive analyses of the codon usage and composition of PVM based on 152 nucleotide sequences of the coat protein (CP) gene and 125 sequences of the cysteine-rich nucleic acid binding protein (NABP) gene. We observed that the PVM CP and NABP coding sequences were GC-and AU-rich, respectively, whereas U- and G-ending codons were preferred in the PVM CP and NABP coding sequences. The lower codon usage of the PVM CP and NABP coding sequences indicated a relatively stable and conserved genomic composition. Natural selection and mutation pressure shaped the codon usage patterns of PVM, with natural selection being the most important factor. The codon adaptation index (CAI) and relative codon deoptimization index (RCDI) analysis revealed that the greatest adaption of PVM was to pepino, followed by tomato and potato. Moreover, similarity Index (SiD) analysis showed that pepino had a greater impact on PVM than tomato and potato. Our study is the first attempt to evaluate the codon usage pattern of the PVM CP and NABP genes to better understand the evolutionary changes of a carlavirus.

The Biology and Phylogenetics of Potato virus S Isolates from the Andean Region of South America.

Biological characteristics of 11 Potato virus S (PVS) isolates from three cultivated potato species (Solanum spp.) growing in five Andean countries and 1 from Scotland differed in virulence depending on isolate and host species. Nine isolates infected Chenopodium quinoa systemically but two others and the Scottish isolate remained restricted to inoculated leaves; therefore, they belonged to biologically defined strains PVSA and PVSO, respectively. When nine wild potato species were inoculated, most developed symptomless systemic infection but Solanum megistacrolobum developed systemic hypersensitive resistance (SHR) with one PVSO and two PVSA isolates. Andean potato cultivars developed mostly asymptomatic primary infection but predominantly symptomatic secondary infection. In both wild and cultivated potato plants, PVSA and PVSO elicited similar foliage symptoms. Following graft inoculation, all except two PVSO isolates were detected in partially PVS-resistant cultivar Saco, while clone Snec 66/139-19 developed SHR with two isolates each of PVSA and PVSO. Myzus persicae transmitted all nine PVSA isolates but none of the three PVSO isolates. All 12 isolates were transmitted by plant-to-plant contact. In infective sap, all isolates had thermal inactivation points of 55 to 60°C. Longevities in vitro were 25 to 40 days with six PVSA isolates but less than 21 days for the three PVSO isolates. Dilution end points were 10-3 for two PVSO isolates but 10-4 to 10-6 with the other isolates. Complete new genome sequences were obtained from seven Andean PVS isolates; seven isolates from Africa, Australia, or Europe; and single isolates from S. muricatum and Arracacia xanthorhiza. These 17 new genomes and 23 from GenBank provided 40 unique sequences; however, 5 from Eurasia were recombinants. Phylogenetic analysis of the 35 nonrecombinants revealed three major lineages, two predominantly South American (SA) and evenly branched and one non-SA with a single long basal branch and many distal subdivisions. Using least squares dating and nucleotide sequences, the two nodes of the basal PVS trifurcation were dated at 1079 and 1055 Common Era (CE), the three midphylogeny nodes of the SA lineages at 1352, 1487, and 1537 CE, and the basal node to the non-SA lineage at 1837 CE. The Potato rough dwarf virus/Potato virus P (PVS/PRDV/PVP) cluster was sister to PVS and diverged 5,000 to 7,000 years ago. The non-SA PVS lineage contained 18 of 19 isolates from S. tuberosum subsp. tuberosum but the two SA lineages contained 6 from S. tuberosum subsp. andigena, 4 from S. phureja, 3 from S. tuberosum subsp. tuberosum, and 1 each from S. muricatum, S. curtilobum, and A. xanthorrhiza. This suggests that a potato-infecting proto-PVS/PRDV/PVP emerged in South America at least 5,000 years ago, became endemic, and diverged into a range of local Solanum spp. and other species, and one early lineage spread worldwide in potato. Preventing establishment of the SA lineages is advised for all countries still without them.

Potato Virus M-Like Nanoparticles: Construction and Characterization.

Virus-like particles (VLPs) are multisubunit self-assembly competent protein structures with identical or highly related overall structure to their corresponding native viruses. To construct a new filamentous VLP carrier, the coat protein (CP) gene from potato virus M (PVM) was amplified from infected potato plants, cloned, and expressed in Escherichia coli cells. As demonstrated by electron microscopy analysis, the PVM CP self-assembles into filamentous PVM-like particles, which are mostly 100-300 nm in length. Adding short Gly-Ser peptide at the C-terminus of the PVM, CP formed short VLPs, whereas peptide and protein A Z-domain fusions at the CP N-terminus retained its ability to form typical PVM VLPs. The PVM-derived VLP carrier accommodates up to 78 amino acid-long foreign sequences on its surface and can be produced in technologically significant amounts. PVM-like particles are stable at physiological conditions and also, apparently do not become disassembled in high salt and high pH solutions as well as in the presence of EDTA or reducing agents. Despite partial proteolytic processing of doubled Z-domain fused to PVM VLPs, the rabbit IgGs specifically bind to the particles, which demonstrates the functional activity and surface location of the Z-domain in the PVM VLP structure. Therefore, PVM VLPs may be recognized as powerful structural blocks for new human-made nanomaterials.

The global trade in fresh produce and the vagility of plant viruses: a case study in garlic.

As cuisine becomes globalized, large volumes of fresh produce are traded internationally. The potential exists for pathogens infecting fresh produce to hitchhike to new locations and perhaps to establish there. It is difficult to identify them using traditional methods if pathogens are novel, scarce, and/or unexpected. In an attempt to overcome this limitation, we used high-throughput sequencing technology as a means of detecting all RNA viruses infecting garlic (Allium sativum L.) bulbs imported into Australia from China, the USA, Mexico, Argentina and Spain, and those growing in Australia. Bulbs tested were grown over multiple vegetative generations and all were stably infected with one or more viruses, including two species not previously recorded in Australia. Present in various combinations from 10 garlic bulbs were 41 virus isolates representing potyviruses (Onion yellow dwarf virus, Leek yellow stripe virus), carlaviruses (Shallot latent virus, Garlic common latent virus) and allexiviruses (Garlic virus A, B, C, D, and X), for which 19 complete and 22 partial genome sequences were obtained, including the first complete genome sequences of two isolates of GarVD. The most genetically distinct isolates of GarVA and GarVX described so far were identified from Mexico and Argentina, and possible scenarios explaining this are presented. The complete genome sequence of an isolate of the potexvirus Asparagus virus 3 (AV3) was obtained in Australia from wild garlic (A. vineale L.), a naturalized weed. This is first time AV3 has been identified from wild garlic and the first time it has been identified beyond China and Japan. The need for routine generic diagnosis and appropriate legislation to address the risks to primary production and wild plant communities from pathogens spread through the international trade in fresh produce is discussed.

Rapid detection of lily symptomless virus with CdTe quantum dots by flow cytometry.

Lily symptomless virus (LSV) is the most common lily virus, being detected in many species and hybrids. We established a microsphere-based fluorescent immunoassay for the determination of LSV, using a polyclonal antibody against LSV covalently bound to carboxy-modified microspheres able to capture LSV antigen. A monoclonal antibody against LSV conjugated to quantum dots (QDs) was used as a fluorescent probe, enabling LSV to be fluorescently detected by a combination of encoded beads and QDs. This method was 16 times more sensitive than ELISA in the detection of LSV, and could potentially be applied to the simultaneous detection of inhomogeneous matter.

Role of the zinc-finger and basic motifs of chrysanthemum virus B p12 protein in nucleic acid binding, protein localization and induction of a hypersensitive response upon expression from a viral vector.

The genomes of carlaviruses encode cysteine-rich proteins (CRPs) of unknown function. The 12 kDa CRP of chrysanthemum virus B (CVB), p12, has been shown previously to induce a hypersensitive response (HR) when expressed from potato virus X (PVX). This study demonstrated that a p12-induced HR was preceded by induction of a number of genes related to pathogenesis, stress and systemic acquired resistance. p12 localized predominantly to the nucleus. Interestingly, it was found that p12 bound both RNA and DNA in vitro, but notably exhibited a preference for DNA in the presence of Zn(2+) ions. Mutational analysis of the p12 conserved sequence motifs demonstrated that the basic motif is required for p12 translocation to the nucleus, thus representing part of the protein nuclear localization signal, whereas the predicted zinc finger motif is needed for both Zn(2+)-dependent DNA binding and eliciting an HR in PVX-infected leaves. Collectively, these results link, for the first time, nuclear localization of the protein encoded by a cytoplasmically replicating virus and its DNA-binding capacity with HR induction. Furthermore, these data suggest that p12 may mediate induction of the host genes by binding to the plant genomic DNA, and emphasize that CVB p12 is functionally distinct from other known nuclear-localized proteins encoded by the plant positive-stranded RNA viruses.

Effect of pH, ions, bovine serum albumin and heterologous antisera on the stability of immunosorbed flexuous potato viruses.

Electron microscopic studies on the stability of immunosorbed (trapped) virions of potato viruses X, S and Y0 (PVX, PVS and PVY0) revealed disintegration and dislodging of PVY0 virions upon incubation with (1) antisera to PVX, PVS, or both diluted in saline, (2) 0.86% NaCl (saline) or 0.1 mol/l CaCl2 but not with 0.1 mol/l CaSO4 or 0.1 mol/l MgSO4. PVX virions, on the other hand, showed partial dislodging upon incubation with an antiserum to PVS diluted in saline, but complete disintegration and dislodging with saline. 0.1 mol/l CaCl2 caused partial dislodging while MgCl2, CaSO4 or MgSO4 (all 0.1 mol/l) had no apparent adverse effect. PVS virions were not affected by saline, CaCl2, MgCl2, CaSO4 or MgSO4 (all 0.1 mol/l) and were only partially dislodged by antisera to PVX or PVY0. Disintegration and/or dislodging of the PVX and PVY0 virions was prevented when (1) they were fixed with glutaraldehyde prior to incubation or (2) the virus extract contained bovine serum albumin (BSA) or (3) heterologous antisera were diluted in 0.1 mol/l phosphate buffer (PB) before use except the PVS antiserum which still caused disintegration and dislodging of PVY0 virions. Prior fixation of virions prevented their disruption and dislodging by saline only in the case of PVY0 but not PVX. On the other hand, BSA reverted the adverse effect of saline but not that of the PVS antiserum on PVY0 virions. The results presented here suggest (1) a disruptive effect of Cl' on PVX and PVY0 virions particularly when it was associated with Na+ and (2) an interaction between the immunosorbed virions of PVX or PVY0 and the antiserum to PVS.