First report of Hibiscus soymovirus in Hibiscus rosa-sinensis in Colombia in mixed infection.

Hibiscus is native to southeast Asia but well suited to Colombia's arid soil and dry climates from the coast to the mountains of Bogotá. Viruses infecting hibiscus in Colombia are largely unexplored, with four viruses previously known: hibiscus chlorotic ringspot virus (HCRSV), hibiscus latent Fort Pierce virus (HLFPV), hibiscus latent Singapore virus (HLSV), and citrus leprosis virus C2 (CiLV-C2) (Padmanabhan et al., 2023). Mixed infections between these viruses were frequently detected. A recent virome analysis of a single hibiscus plant from Colombia revealed multiple viruses in mixed infection; : HCRSV, HLFPV, passion fruit green spot virus (PFGSV), a strain of physalis vein necrosis nepovirus, four novel carlavirus, one new potexvirus and a mitovirus. In addition, few smaller contigs of blunervirus and soymovirus were also identified in the high throughput sequencing (HTS) data, but their presence in the mixed infection could not be validated (A. Roy et al. 2023unpublish data). During Brevipalpus-transmitted virus (BTV) surveys, two asymptomatic and 15 hibiscus foliar samples showing green ringspots with central chlorotic spots in senescing areas, mosaic, and black or chlorotic spots were collected from six departments (states) in three geographical regions of Colombia: Tolima (n=4) and Cauca Valley (n=2) (Andean region), Meta (n=6) and Casanare (n=1) (Orinoquia region), and Quindío (n=1) and Risaralda (n=1) (coffee growing region). About 100 mg of 17 hibiscus leaf samples were separately processed for RNA isolation without DNase I treatment and tested for known BTVs, and for newly discovered hibiscus soymovirus (HSV; genus Soymovirus family Caulimoviridae) using PCR assays (Padmanabhan et al. 2023, Wang et al. 2023). To identify potential HSV infection in the samples, published SVF1/SVR1 and newly designed primer pairs (HSV-REP-F/-R and HSV-CPG-F/-R) were used to amplify the 430 nt transactivation (ORF-VI), 631 nt replicase (REP) and 401 nt coat protein gene (CPG), respectively (Supplementary 1). Of 17 samples tested, three from Tolima and one each from Meta and Quindío yielded all three expected size amplicons. Bi-directional sequencing followed by BLASTn analysis revealed 95-98% nt identity with the CPG, REP, and ORF-VI genes of HSV (OP757659). Ribo-depleted libraries were prepared using the RNA extracts of five HSV PCR positive samples. HTS yielded 11.6 to 50.3 million raw reads per sample library. Adapters were trimmed and filtered from the raw reads with Trimmomatic v0.39 and then assembled using SPAdes v3.15.5 (Padmanabhan et al., 2023). Contigs were blasted against the Arabidopsis proteome and a RefSeq-based viral protein database. Potential viral sequences were then blasted against the complete NCBI nr database. Assembled soymo contigs covered 99-100% of the HSV genome, with per-nucleotide read depths of 23.8 to 393. Contigs from the Tolima (Accessions; OR621030- OR621032 and Quindío samples (OR621033) covered 99-100% of the HSV genome and had >96-98% nt identity to Hawaiian isolate (OP757659) whereas the Meta sample contigs covered 78% of the genome with 9495% nt identity. HTS contigs shared >98-99% nt identities with their PCR amplicons. Along with HSV, other virus sequences (HCRSV, HLFPV, PFGSV, CiLV-C2, and mycoviruses) were variously detected from all five libraries. Due to mixed infection no symptom similarity was noticed among these 5 samples. The findings in hibiscus in Tolima, Meta and Quindío represent the first confirmed report of HSV infection in hibiscus in Colombia. The widespread distribution suggests the possibility of HSV dispersion via movement of planting material, and potential further spread to another hibiscus growing region.

First report of Passion fruit green spot virus in yellow Passion fruit (Passiflora edulis f. flavicarpa) in Casanare, Colombia.

Passiflora edulis, commonly known as passion fruit, is a vine species of passionflower native to South America. In Colombia, yellow passion fruit (P. edulis f. flavicarpa) is the most important species in terms of net production and local consumption. Recently two brevipalpus transmitted cileviruses, (i) passion fruit green spot virus (PfGSV) and (ii) hibiscus strain of citrus leprosis virus C2 (CiLV-C2H) were detected in passion fruit in Brazil and Hawaii, respectively (Ramos-González et al., 2020, Olmedo-Velarde et al., 2022). CiLV-C2H infects both citrus and hibiscus in Colombia (Roy et al., 2015, 2018) but there was no report of PfGSV elsewhere apart from Brazil and Paraguay (Costa-Rodrigues et al., 2022). Apart from emerging begomovirus diseases, five major viruses are known to infect passion fruit in Colombia: soybean mosaic virus (SMV), cowpea aphid-borne mosaic virus, passion fruit yellow mosaic virus, cucumber mosaic virus, and a tentative Gulupa bacilliform badnavirus A (Cardona et al., 2022). Current findings of CiLV-C2H in passion fruit and PfGSV in hibiscus motivated us to investigate the possibilities of cilevirus infection in passion fruit in Colombia. During surveys, along with healthy yellow passion fruit leaves, five symptomatic plant samples from Meta and three from Casanare were collected before sent to the Molecular Plant Pathology Laboratory at Beltsville, MD under APHIS permit. Passion fruit samples from Meta showed leaf mottling, rugose mosaic, and leaf distortion, whereas leaf variegation, chlorotic spots, yellowing, green spots in senescent leaves and green vein banding were observed in the Casanare samples (Supp. Fig. 1). Total RNA was extracted using RNeasy Plant Mini Kit (Qiagen, USA). To know the potential cilevirus infection in these samples, three PfGSV specific (Ramos-González et al. 2020) and a CiLV-C2 generic primer pairs (Olmedo-Velarde et al. 2021) were used in the RT-PCR assays. All five passion fruit samples from Meta failed to produce either CiLV-C2 or CiLV-C2H or PfGSV amplicon whereas all three Casanare samples successfully amplified 321, 244 and 299 nts of PfGSV-RNA1 and -RNA2 amplicons using C13F/C13R, C6F/C6R and C8F/C8R primers, respectively. Bi-directional amplicon sequencing followed by BlastN analysis revealed ≥99% nt identity with the PfGSV-RNA1 (MK804173) and -RNA2 (MK804174) genome sequences. An optimized ribo-depleted library preparation protocol was utilized to prepare two cDNA libraries using the RNA extracts of a PfGSV suspected positive (Casanare) and a negative (Meta) samples (Chellappan et al., 2022). HTS libraries of Casanare and Meta samples resulted in 22.7 to 29.5 million raw reads, respectively. After adapter trimming and filtering, clean reads were mapped to the Arabidopsis thaliana reference genome and unmapped reads were de novo assembled (Chellappan et al., 2022). BlastN analysis from the assembled contigs identified 1-3 contigs corresponding to PfGSV-RNA1 and -RNA2, respectively, from Casanare sample whereas 3 contigs of SMV were identified in Meta passion fruit sample. No other virus sequence was obtained from either of the libraries. Assembled contigs covered 99.33% of the RNA1 and 94.42% of the RNA2 genome, with read depths of 64,474 and 119,549, respectively. Meta sample contigs (OP564897) covered >99% of the SMV genome, which shared >99% nt identity with the Colombian SMV isolates (KY249378, MW655827). Both RNA-1 (OP564895) and -2 (OP564896) segments of the Casanare isolate shared 99% nt identity with PfGSV isolate (MK804173-74). Our discovery identified PfGSV in Colombia, for the first-time outside Brazil and Paraguay. The findings of PfGSV in yellow passion fruit increases the potential threat and possibility of PfGSV movement via Brevipalpus sp. from passion fruit to other hosts.

Immunodiagnosis of Citrus leprosis virus C using a polyclonal antibody to an expressed putative coat protein.

Citrus leprosis virus C (CiLV-C), a causal agent for citrus leprosis disease, is present in South and Central America and is a threat for introduction into the U.S. citrus industry. A specific, inexpensive and reliable antibody based detection system is needed for the rapid identification of CiLV-C. The CiLV-C is very labile and has not been purified in sufficient amount for antibody production. The p29 gene of CiLV-C genome that codes for the putative coat protein (PCP) was codon optimized for expression in Escherichia coli and synthesized in vitro. The optimized gene was sub-cloned into the bacterial expression vector pDEST17 and transferred into E. coli BL21AI competent cells. The expression of PCP containing N-terminal His-tag was optimized by induction with l-arabinose. Induced cells were disrupted by sonication and expressed PCP was purified by affinity chromatography using Ni-NTA agarose. The purified expressed PCP was then used as an immunogen for injections into rabbits to produce polyclonal antibody (PAb). The PAb specific to the expressed PCP was identified using Western blotting. The antibody was successfully used to detect CiLV-C in the symptomatic CiLV-C infected tissues using double antibody sandwich-enzyme-linked-immunosorbent (DAS-ELISA), indirect ELISA and dot-blot immunoassay (DBIA) formats.

A novel virus of the genus Cilevirus causing symptoms similar to citrus leprosis.

Citrus leprosis in Colombia was previously shown to be caused by cytoplasmic Citrus leprosis virus (CiLV-C). In 2011, enzyme-linked immunosorbent assay and reverse-transcription polymerase chain reaction (RT-PCR)-based diagnostic methods failed to identify CiLV-C from citrus samples with symptoms similar to citrus leprosis; however, virions similar to CiLV-C were observed in the cytoplasm of the symptomatic leaves by transmission electron microscopy. Furthermore, the causal organism was transmitted by the false spider mite, Brevipalpus phoenicis, to healthy citrus seedlings. A library of small RNAs was constructed from symptomatic leaves and used as the template for Illumina high-throughput parallel sequencing. The complete genome sequence and structure of a new bipartite RNA virus was determined. RNA1 (8,717 nucleotides [nt]) contained two open reading frames (ORFs). ORF1 encoded the replication module, consisting of five domains: namely, methyltransferase (MTR), cysteine protease-like, FtsJ-MTR, helicase (Hel), and RNA-dependent RNA polymerase (RdRp); whereas ORF2 encoded the putative coat protein. RNA2 (4,989 nt) contained five ORFs that encode the movement protein (MP) and four hypothetical proteins (p7, p15, p24, and p61). The structure of this virus genome resembled that of CiLV-C except that it contained a long 3' untranslated terminal region and an extra ORF (p7) in RNA2. Both the RNA1 and RNA2 of the new virus had only 58 and 50% nucleotide identities, respectively, with known CiLV-C sequences and, thus, it appears to be a novel virus infecting citrus. Phylogenetic analyses of the MTR, Hel, RdRp, and MP domains also indicated that the new virus was closely related to CiLV-C. We suggest that the virus be called Citrus leprosis virus cytoplasmic type 2 (CiLV-C2) and it should be unambiguously classified as a definitive member of the genus Cilevirus. A pair of CiLV-C2 genome-specific RT-PCR primers was designed and validated to detect its presence in citrus leprosis samples collected from the Casanare and Meta states in Colombia.