An Unwanted Association: The Threat to Papaya Crops by a Novel Potexvirus in Northwest Argentina.

An emerging virus isolated from papaya (Carica papaya) crops in northwestern (NW) Argentina was sequenced and characterized using next-generation sequencing. The resulting genome is 6667-nt long and encodes five open reading frames in an arrangement typical of other potexviruses. This virus appears to be a novel member within the genus Potexvirus. Blast analysis of RNA-dependent RNA polymerase (RdRp) and coat protein (CP) genes showed the highest amino acid sequence identity (67% and 71%, respectively) with pitaya virus X. Based on nucleotide sequence similarity and phylogenetic analysis, the name papaya virus X is proposed for this newly characterized potexvirus that was mechanically transmitted to papaya plants causing chlorotic patches and severe mosaic symptoms. Papaya virus X (PapVX) was found only in the NW region of Argentina. This prevalence could be associated with a recent emergence or adaptation of this virus to papaya in NW Argentina.

Geographical distribution, genetic studies and vector transmission of alfalfa enamovirus-1 infecting alfalfa crop in Argentina.

Alfalfa (Medicago sativa L.) growing areas of Argentina were surveyed between 2010 and 2018 to determine the geographical distribution and analyse the genetic diversity among alfalfa enamovirus-1 (AEV-1) isolates. The virus was detected in all 17 surveyed alfalfa-producing provinces, with a prevalence of 64%. The plant virus AEV-1 is widely distributed in the country, and its transmission vector has been unknown until now. Here we show that the black aphid Aphis craccivora can transmit AEV-1. The CP sequence identity among 16 AEV-1 isolates from Argentina was from 98 to 100% and from 98.9 to 100% at nucleotide and amino acid levels, respectively, indicating a low level of sequence variation among these isolates. The phylogenetic analysis based on the complete nucleotide sequence of the CP gene indicated that AEV-1 isolates are closely related and clustered in a monophyletic group. These results suggest that AEV-1 has spread very recently in Argentina. In the present study, we report the geographical distribution of AEV-1 in the main alfalfa-growing areas of Argentina and, for the first time, identify an insect vector and describe the CP gene diversity of an enamovirus worldwide.

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.

Redefining the medicago sativa alphapartitiviruses genome sequences.

In alfalfa samples analyzed by hightroughput sequencing, four de novo assembled contigs encoding gene products showing identities to alphapartitiviruses proteins were found based on BlastX analysis. The predicted amino acid (aa) sequences of two contigs presented 99-100% identity to the RNA-dependent RNA polymerase (RdRp) and the capsid protein (CP) of the recently reported medicago sativa alphapartitivirus 1 (MsAPV1). In addition, the remaining two contigs shared only 56% (CP) and 70% (RdRp) pairwise aa identity with the proteins of MsAPV1, suggesting that these samples presented also a novel Alphapartitivirus species. Further analyses based on complete genome segments termini and the presence/absence of alphapartitivirus RNA in several samples and public alfalfa RNA datasets corroborated the identification of two different alphapartitivirus members. Our results likely indicate that the reported MsAPV1 genome was previously reconstructed with genome segments of two different alphapartitiviruses. Overall, we not only revisited the MsAPV1 genome sequence but also report a new tentative alphapartitivirus species, which we propose the name medicago sativa alphapartitivirus 2. In addition, the RT-PCR detection of both MsAPV1 and MsAPV2 in several alfalfa cultivars suggests a broad distribution of both viruses.

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.