Early-Stage Phenotyping of Sweet Potato Virus Disease Caused by Sweet Potato Chlorotic Stunt Virus and Sweet Potato Virus C to Support Breeding.

Sweet potato virus disease (SPVD) is a global constraint to sweetpotato (Ipomoea batatas) production, especially under intensive cultivation in the humid tropics such as East Africa. The objectives of this study were to develop a precision SPVD phenotyping protocol, to find new SPVD-resistant genotypes, and to standardize the first stages of screening for SPVD resistance. The first part of the protocol was based on enzyme-linked immunosorbent assay results for sweet potato chlorotic stunt virus (SPCSV) and sweet potato virus C (SPVC) with adjustments to a negative control (uninfected clone Tanzania) and was performed on a prebreeding population (VZ08) comprising 455 clones and 27 check clones graft inoculated under screenhouse conditions. The second part included field studies with 52 selected clones for SPCSV resistance from VZ08 and 8 checks. In screenhouse conditions, the resistant and susceptible check clones performed as expected; 63 clones from VZ08 exhibited lower relative absorbance values for SPCSV and SPVC than inoculated check Tanzania. Field experiments confirmed SPVD resistance of several clones selected by relative absorbance values (nine resistant clones in two locations; that is, 17.3% of the screenhouse selection), supporting the reliability of our method for SPVD-resistance selection. Two clones were promising, exhibiting high storage root yields of 28.7 to 34.9 t ha-1 and SPVD resistance, based on the proposed selection procedure. This modified serological analysis for SPVD-resistance phenotyping might lead to more efficient development of resistant varieties by reducing costs and time at early stages, and provide solid data for marker-assisted selection with a quantitative tool for classifying resistance.[Formula: see text] Copyright © 2023 The Author(s). This is an open access article distributed under the CC BY 4.0 International license.

Phylogenetics and Evolution of Potato Virus V: Another Potyvirus that Originated in the Andes.

Potato virus V (PVV) causes a disease of potato (Solanum tubersosum) in South and Central America, Europe, and the Middle East. We report here the complete genomic sequences of 42 new PVV isolates from the potato's Andean domestication center in Peru and of eight historical or recent isolates from Europe. When the principal open reading frames of these genomic sequences together with those of nine previously published genomic sequences were analyzed, only two from Peru and one from Iran were found to be recombinant. The phylogeny of the 56 nonrecombinant open reading frame sequences showed that the PVV population had two major phylogroups, one of which formed three minor phylogroups (A1 to A3) of isolates, all of which are found only in the Andean region of South America (Peru and Colombia), and the other formed two minor phylogroups, a basal one of Andean isolates (A4) that is paraphyletic to a crown cluster containing all the isolates found outside South America (World). This suggests that PVV originated in the Andean region, with only one minor phylogroup spreading elsewhere in the world. In minor phylogroups A1 and A3, there were two subclades on long branches containing isolates from S. phureja evolving more rapidly than the others, and these interfered with dating calculations. Although no temporal signal was directly detected among the dated nonrecombinant sequences, PVV and potato virus Y (PVY) are from the same potyvirus lineage and are ecologically similar, so "subtree dating" was done via a single maximum likelihood phylogeny of PVV and PVY sequences, and PVY's well-supported 157 ce "time to most common recent ancestor" was extrapolated to date that of PVV as 29 bce. Thus the independent historical coincidences supporting the datings of the PVV and PVY phylogenies are the same; PVV arose ≥2,000 years ago in the Andes and was taken to Europe during the Columbian Exchange, where it diversified around 1853 ce, soon after the European potato late blight pandemic. PVV is likely to be more widespread than currently realized and is of biosecurity relevance for world regions that have not yet recorded its presence.[Formula: see text] Copyright © 2022 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

Phylodynamics of sunflower chlorotic mottle virus, an emerging pathosystem.

Distribution and epidemiological patterns of sunflower chlorotic mottle virus (SCMoV) in sunflower (Helianthus annuus L.) growing areas in Argentina were studied from 2006 to 2017. The virus was detected exclusively in the Pampas region (Entre Ríos, Santa Fe, Córdoba, La Pampa and Buenos Aires provinces). Phylodynamic analyses performed using the coat protein gene of SCMoV isolates from sunflower and weeds dated the most recent common ancestor (MRCA) back to 1887 (HPD95% = 1572-1971), which coincides with the dates of sunflower introduction in Argentina. The MRCA was located in the south of Buenos Aires province and was associated with sunflower host (posterior probability for the ancestral host, ppah = 0.98). The Bayesian phylodynamic analyses revealed the dispersal patterns of SCMoV, suggesting a link between natural host diversity, crop displacement by human activities and virus spread.

Molecular characterization and complete genome of alstroemeria mosaic virus (AlMV).

Even though alstroemeria mosaic virus (AlMV) is one of the most important viruses affecting alstroemeria plants, its genome is only partially available in public sequence databases. High throughput sequencing (HTS) of RNA from alstroemeria plants with symptoms of mosaic and streaking, collected in Lasso-Ecuador, indicated the presence of AlMV and lily symptomless virus. In this study, we aimed to assemble and characterize the complete genome sequence of AlMV. Reads from Illumina sequencing of ribosomal RNA-depleted total RNA were assembled into contigs that were mapped to the sunflower chlorotic mottle virus genome, revealing the 9774 [corrected] bp complete genome sequence of AlMV. Multiple sequence alignment of the AlMV polyprotein with close homologs allowed the identification of ten mature proteins P1, HC-Pro, P3, 6K1, CI, 6K2, NIa-VPg, NIa-Pro, NIb and CP. Furthermore, several potyvirus motifs were identified in the AlMV polyprotein including those related to potyvirus aphid transmission 334KMTC337, 592PTK594 and 2800DAG2802. Phylogenetic analysis based in the polyprotein showed that AlMV belongs to the potato virus Y clade and its closest relative is sunflower ring blotch virus. This study describes the first complete genome of AlMV and its placement within the genus Potyvirus, providing valuable information for future studies on this economically important virus.

Biological and Molecular Properties of Wild potato mosaic virus Isolates from Pepino (Solanum muricatum).

In 1976, a virus with flexuous, filamentous virions typical of the family Potyviridae was isolated from symptomatic pepino (Solanum muricatum) plants growing in two valleys in Peru's coastal desert region. In 2014, a virus with similar-shaped virions was isolated from asymptomatic fruits obtained from pepino plants growing in six coastal valleys and a valley in Peru's Andean highlands. Both were identified subsequently as Wild potato mosaic virus (WPMV) by serology or high-throughput sequencing (HTS). The symptoms caused by two old and seven new isolates from pepino were examined in indicator plants. Infected solanaceous hosts varied considerably in their sensitivities to infection and individual isolates varied greatly in virulence. All seven new isolates caused quick death of infected Nicotiana benthamiana plants and more than half of them killed infected plants of Physalis floridana and S. chancayense. These three species were the most sensitive to infection. The most virulent isolate was found to be BA because it killed five of eight solanaceous host species whereas CA was the least severe because it only killed N. benthamiana. Using HTS, complete genomic sequences of six isolates were obtained, with one isolate (FE) showing evidence of recombination. The distances between individual WPMV isolates in phylogenetic trees and the geographical distances between their collection sites were found to be unrelated. The individual WPMV isolates displayed nucleotide sequence identities of 80.9-99.8%, whereas the most closely related virus, Potato virus V (PVV), was around 75% identical to WPMV. WPMV, PVV, and Peru tomato virus formed clusters of similar phylogenetic diversity, and were found to be distinct but related viruses within the overall Potato virus Y lineage. WPMV infection seems widespread and of likely economic significance to pepino producers in Peru's coastal valleys. Because it constitutes the fifth virus found infecting pepino and this crop is entirely vegetatively propagated, development of healthy pepino stock programs is advocated.

Characterization of the genome of a novel ilarvirus naturally infecting Cape gooseberry (Physalis peruviana).

As part of an initiative to characterize viruses infecting Cape gooseberry in the province of Antioquia (Colombia), we report the genome sequence of a new member of the genus Ilarvirus (family Bromoviridae). This virus was identified in a Cape gooseberry plot in the municipality of Marinilla in a mixed infection with potato virus Y (PVY) as part of high-throughput sequencing initiative. Results were confirmed by nested RT-PCR and DAS-ELISA. Phylogenetic analysis suggested that the Cape gooseberry ilarvirus is a new member of subgroup 1 and it is most closely related to ageratum latent virus (AgLV). The name "Cape gooseberry ilarvirus 1" (CGIV-1) is proposed for this new ilarvirus.

Identification and characterization of a new potyvirus infecting cucurbits.

A new potyvirus, tentatively named cucurbit vein banding virus (CVBV), was identified in crops of cucurbits in San Pedro (Buenos Aires, Argentina). The complete genome sequences of two isolates of CVBV were obtained by next-generation sequencing (Illumina). The genomic RNA consisted of 9968 and 9813 nucleotides, respectively, and displayed typical potyvirus organization. The percentage identity for these two genome sequences, using BLASTn, was 77% to sweet potato virus c and 73% to tomato necrotic stunt virus. BLASTx analysis of the complete polyprotein showed that the most closely related virus is plum pox virus, with 48% amino acid sequence identity for both isolates. Sequence comparisons and phylogenetic analyses indicate that CVBV belongs to a previously undescribed species in genus Potyvirus.

Complete genome sequence of sunflower ring blotch virus, a new potyvirus infecting sunflower in Argentina.

The complete genome sequence of sunflower ring blotch virus (SuRBV), a previously undescribed potyvirus infecting sunflower in Argentina, is reported. The SuRBV genome comprises 9555 nucleotides (nt) and encodes a polyprotein of 3061 amino acids, flanked by 5' and 3' untranslated regions of 117 and 255 nt, respectively. Phylogenetic analysis showed that SuRBV belongs to the potato virus Y (PVY) subgroup and clusters together with sunflower chlorotic mottle virus and bidens mosaic virus. Percentage nucleotide identity between the whole genomes of SuRBV and BiMV was 70.6%, suggesting SuRBV should be considered a distinct species in the genus Potyvirus.

Biological, serological and molecular typing of potato virus Y (PVY) isolates from Tunisia.

In Tunisia, potato virus Y (PVY) currently presents a significant threat to potato production, reducing tuber yield and quality. Three hundred and eighty-five potato samples (six different cultivars) collected in autumn 2007 from nine regions in Tunisia were tested for PVY infection by DAS-ELISA. The virus was detected in all regions surveyed, with an average incidence of 80.26%. Subsequently, a panel of 82 Tunisian PVY isolates (PVY-TN) was subjected to systematic biological, serological and molecular typing using immunocapture reverse-transcription polymerase chain reaction and a series of PVYOC- and PVYN-specific monoclonal antibodies. Combined analyses revealed ~67% of PVYNTN variants of which 17 were sequenced in the 5'NTR-P1 region to assess the genetic diversity and phylogenetic relationship of PVY-TN against other worldwide PVY isolates. To investigate whether selective constraints could act on viral genomic RNA, synonymous and non-synonymous substitution rates and their ratio were analyzed. Averages of all pairwise comparisons obtained in the 5'NTR-P1 region allowed more synonymous changes, suggesting selective constraint acting in this region. Selective neutrality test was significantly negative, suggesting a rapid expansion of PVY isolates. Pairwise mismatch distribution gave a bimodal pattern and pointed to an eventually early evolution characterizing these sequences. Genetic haplotype network topology provided evidence of the existence of a distinct geographical structure. This is the first report of such genetic analyses conducted on PVY isolates from Tunisia.

Biological and molecular characterization of a highly divergent johnsongrass mosaic virus isolate from Pennisetum purpureum.

The complete genome sequence (9,865 nucleotides) of a highly divergent johnsongrass mosaic virus isolate (JGMV-CNPGL) was determined using Illumina sequencing. This isolate infected 10 genotypes of gramineous plants including maize. A comparative analysis of the complete genome showed 80 % nucleotide (nt) sequence identity (86 % amino acid (aa) sequence identity) to a johnsongrass mosaic virus isolate from Australia. The coat protein (CP) identity values, however, were lower than those for the whole genome (78 % and 80 % for nt and aa, respectively) and were close to the species demarcation values (77 % nt and 80 % aa). Unexpectedly, the amino-terminal portion of CP of JGMV-CNPGL showed only 38 % sequence identity to other JGMV isolates. The biological implications of this sequence divergence remain to be elucidated.

Genome sequence of a divergent Colombian isolate of potato virus V (PVV) infecting Solanum phureja.

Deep sequencing analysis of the transcriptome of a Solanum phureja cv. Criolla Colombia plant with symptoms typical of a virus disease revealed an infection with potato virus V (PVV). The PVV-phureja genome comprises 9904 nt, exhibits 83% nucleotide identity with currently fully sequenced PVV isolates and contains one large ORF that codes for a polyprotein of 3065 residues flanked by 5' and 3' UTR of 217 and 448 nt, respectively. Phylogenetic analysis of the PVV-phureja polyprotein indicates that it is divergent with respect to most PVV isolates. This is the first complete PVV genome of an isolate infecting a host different to S. tuberosum and, to this date, the only one from the South American Andes.

Genome sequence of a virus isolate from tamarillo (Solanum betaceum) in Colombia: evidence for a new potyvirus.

Based on the results of a deep sequencing transcriptome study of tamarillo (Solanum betaceum), we report the genome sequence of a virus from this host plant. Since this probably represents a new member of the genus Potyvirus, the name tamarillo leaf malformation virus (TaLMV) has been proposed. Phylogenetic analysis reveals that TaLMV is the closest relative of Colombian datura virus (CDV), followed by three other potyviruses: tobacco etch virus, potato virus A and tobacco vein mottling virus. This is the first sequence of a potyvirus infecting Solanum betaceum containing the complete polyprotein coding region.

Complete genome sequence of arracacha mottle virus.

Arracacha mottle virus (AMoV) is the only potyvirus reported to infect arracacha (Arracacia xanthorrhiza) in Brazil. Here, the complete genome sequence of an isolate of AMoV was determined to be 9,630 nucleotides in length, excluding the 3' poly-A tail, and encoding a polyprotein of 3,135 amino acids and a putative P3N-PIPO protein. Its genomic organization is typical of a member of the genus Potyvirus, containing all conserved motifs. Its full genome sequence shared 56.2 % nucleotide identity with sunflower chlorotic mottle virus and verbena virus Y, the most closely related viruses.

Complete nucleotide sequence of an Argentinean isolate of sweet potato virus G.

Sweet potato virus G belongs to the largest plant virus genus Potyvirus. This virus was detected for the first time in Argentina and then sequenced using the method of next-generation pyrosequencing. The complete genome was found to be 10,798 nucleotides excluding the poly-A tail with a predicted genome organization typical for a member of the genus Potyvirus. This is the first report of the complete genomic sequence of a SPVG isolated from South America.

Complete genome sequence of pepper yellow mosaic virus, a potyvirus, occurring in Brazil.

The complete genomic sequence of pepper yellow mosaic virus (PepYMV), a member of the genus Potyvirus, was determined. The sequence was 9745 nucleotides long, excluding the 3' poly(A) tail. The genome contained a large open reading frame encoding a polyprotein of 3085 amino acids, which contained the typically conserved motifs found in members of the genus Potyvirus and an additional P3-PIPO (pretty interesting potyvirus ORF). In a pairwise comparison with other potyvirus sequences, the full genome of PepYMV shared a maximum of 63.84 % nucleotide sequence identity with pepper mottle virus (PepMoV), followed by verbena virus Y (VVY, 62.11 %), potato virus Y (PVY, 62.07 %) and Peru tomato mosaic virus (PTV, 62.00 %). Based upon a phylogenetic analysis, PepYMV was most closely related to PepMoV and PTV, within the PVY subgroup cluster, like most potyviruses isolated in solanaceous hosts in South America.

Phylogeography and molecular epidemiology of Papaya ringspot virus.

Papaya ringspot virus (PRSV) is the most important virus affecting papaya and cucurbit plants in tropical and subtropical areas. PRSV isolates are divided into biotypes P and W: both the P and W types naturally infect plants in the family Cucurbitaceae, whereas the P type naturally infects papaya (Carica papaya). Understanding the origin and nature of the PRSV genetic diversity and evolution is critical for the implementation of control strategies based on cross-protection and the deployment of transgenic plants that show resistance to virus isolates highly similar to the transgene. The molecular epidemiology of PRSV was evaluated by analyzing the nucleotide sequence of the capsid protein (CP) and helper component-proteinase (HC-Pro) genes of isolates from around the world, including newly characterized ones from Colombia and Venezuela, using a relaxed molecular clock-based approach and a phylogeographic study. Our results confirm previous estimates on the origin of PRSV around 400 years ago and suggest distinct dispersion events from the Indian Peninsula to the rest of Asia, via Thailand, and subsequently to the Americas. A historical reconstruction of the P- and W-type characters in the phylogenetic study supports the need to revise the hypothesis that PRSV-P derives from PRSV-W since our results suggest that the ancestral state could be either of the two biotypes. Moreover, estimates of epidemic growth predict an increasing genetic diversity of the virus over time that has direct implications for control strategies of PRSV based on cross-protection and the use of transgenic plants.

Analysis of complete genomic sequences of isolates of the Sweet potato feathery mottle virus strains C and EA: molecular evidence for two distinct potyvirus species and two P1 protein domains.

The complete nucleotide sequence of the isolate C1 of Sweet potato feathery mottle virus (SPFMV) strain C and the 5' region of several other strains were determined and analyzed together with the sequences of isolates representing the EA, RC and O strains. This provided molecular evidence for the reclassification of SPFMV strains into two species and the occurrence of a complex recombinant isolate. Analysis also revealed a hypervariable domain in the P1 protein, which separates an N-terminal region unique to SPFMV and members of the ipomovirus species Sweet potato mild mottle virus from the C-terminal protease domain, which is conserved among all potyviruses.

Molecular characterization of Sunflower chlorotic mottle virus: a member of a distinct species in the genus Potyvirus.

The complete nucleotide (nt) and deduced amino acid (aa) sequences of the C (common) and CRS (chlorotic ringspot) Argentine strains of SuCMoV have been determined. The SuCMoV-C RNA genome consists of 9,965 nt, whereas indels within the P1 coding region of SuCMoV-CRS make its genomic length 15 nt shorter. Nucleotide and aa sequence identities between the polyproteins of the C and CRS strains of SuCMoV were 92.3 and 95.6%, respectively. Pairwise comparisons between the polyproteins of the C and CRS strains of SuCMoV and the viruses of the Potato virus Y (PVY) subgroup revealed identities of 66.5-66.9% at the nt level and 69.7-69.8% at the aa level. These results and phylogenetic analyses show that although SuCMoV strains cluster together with the potyviruses belonging to the PVY subgroup, SuCMoV should be considered a member of a distinct species in the genus Potyvirus.

Presence of necrotic strains of Potato virus Y in Mexican potatoes.

As part of a routine screening for the possible presence of the necrotic strains of potato virus Y affecting potatoes in Mexico, five PVY isolates were submitted to biological and molecular analysis. Considering their serological properties, two belong to the common strain (O) and three to the necrotic strain (N). All the isolates induced vein necrosis in Nicotiana tabacum. To characterize the isolates, 5' NTR and P1 genes were sequenced and compared with sequences from GenBank database. Nucleotide sequence similarity ranged from 47-100% in the 5' NTR and from 63-100% in the P1 coding region. The lowest amino acid similarity between sequences of P1 gene was 55%. In phylogenetic trees of 5'NTR analysis, two PVY(O) Mexican isolates clustered with other PVY(O) isolates. In turn, the three PVY(N) isolates grouped with PVY(N-NTN) isolates. The phylogenetic analysis of P1 sequences (nucleotide and amino acid) showed two PVY(O) isolates grouping next to N-NTN cluster. A detailed analysis of the PVY(O) isolates showed two potential recombination regions in the P1 gene, in contrast to 5'NTR where no recombination was detected.

Rapid identification of viruses causing sugarcane mosaic by direct sequencing of RT-PCR products from crude extracts: a method for large scale virus surveys.

Sugarcane mosaic virus (SCMV) and sorghum mosaic virus (SrMV) diversity studies are important to characterize virus populations in sugarcane producing areas, enabling (i) identification of shifts in predominant strains, (ii) detecting associations of strains with specific varieties, and (iii) possibly exposing the appearance of new strains which may affect the performance of varieties in a region. Recent studies have shown significant sequence variability within SCMV populations around the world, indicating that isolate identification would be best achieved by direct analysis of sequence data. Because virus sequence-based studies that require the characterization of large numbers of isolates may be impractical using standard sample preparation and processing methodology, a simple protocol that yields quality sequence information, requiring neither viral RNA purification nor cloning of RT-PCR products was developed. Rapid virus release extracts are obtained by submerging a portion of leaf tissue into an extraction buffer, followed by a brief incubation at 95 degrees C. An aliquot of the extract is pipetted into an RT-PCR amplification mix for the detection of SCMV and the SrMV coat protein gene fragments. RT-PCR fragments are sequenced directly using oligonucleotide primers similar to the RT-PCR primers, yielding sequence information of an adequate quality. This rapid, cost effective protocol is practical for large scale virus diversity and evolutionary studies.