First Report of Tomato leaf curl Albatinah virus (ToLCABV) and its Associated Betasatellite Infecting Papaya in Oman.

Leaf curl disease with severe curling, vein darkening, and vein thickening was observed on papaya plants in a field in Qurayat district of Oman during December 2013. Disease incidence ranged from 50 to 70%, particularly in young papaya plants. The presence of a large population of whiteflies and symptoms observed on papaya plants suggested that the causal agent could be begomoviruses (family Geminiviridae) and associated satellites. Four leaf samples with mild and severe leaf curling were collected from the field. Total nucleic acid extracted from symptomatic and healthy plants using the CTAB method were used as a template to amplify circular DNAs using Φ29 DNA polymerase, and products were digested with restriction enzymes to identify fragments of 2.6 to 2.8 kb typical of geminiviruses. BamHI yielded fragments of ~2.8 and 1.4 kb when the digested products were resolved by electrophoresis on a 1% agarose gel. These fragments were cloned and sequenced using a primer walking strategy in both directions. Sequencing results confirmed the exact sizes of 1,303, 1,358, and 2,765 bp; the sequences were deposited in GenBank under the accession numbers HG969296, HG969297, and HG969260, respectively. BLAST results showed that the first two sequences are Tomato leaf curl betasatellite (ToLCB; isolates Pap-2 and Pap-3) showing 97% sequence identity with a previously reported ToLCB sequence (Accession No. KF229728). Both satellites encode a single gene in the complementary sense strand referred to as ßC1, which showed 97% sequence identity to ToLCB (HE800551). The viral sequence (isolate Pap-6) showed four genes in the complementary sense (the replication-associated protein [Rep] gene, the transcription-activator protein [TrAP] gene, the replication-enhancer protein [REn] gene, and the C4 gene) and two genes (pre-coat protein [V2] and coat protein [CP]) in virion-sense (2). BLAST analysis showed 95.2% sequence identity to Tomato leaf curl Albatinah virus (ToLCABV; FJ956700), reported earlier to infect tomato in Oman (3). Amino acid sequence comparison of the four predicted proteins (Rep, TrAP, Ren, and C4) encoded by Pap-6 shared 95, 96, 100, and 100% sequence identity, whereas virion-sense proteins (V1 and V2) shared 99% sequence identity with ToLCABV (FJ956700). According to the recommendations of the International Committee on Taxonomy of Viruses, these results indicate that the virus identified in association with papaya leaf curl disease in Oman is a variant of ToLCABV (1). All infected samples showed the presence of ToLCABV, while no hybridization was observed in healthy control DNA using ToLCABV probe. These findings are indicative of the rapid spread of diseases involving Begomovirus and betasatellites, which often result in increased host range, as is evident from this study. References: (1) C. M. Fauquet et al. Arch. Virol. 148:405, 2003. (2) L. Hanley-Bowdoin et al. Crit. Rev. Plant Sci. 18:71, 1999. (3) A. J. Khan et al. Arch. Virol. 159:445, 2013.

Identification of Chili leaf curl virus Causing Leaf Curl Disease of Petunia in Oman.

Petunias (Petunia × hybrida) are the most important ornamental plants in Oman. In 2012, petunias were observed in public parks and airport landscape in Dhofar region with symptoms of upward leaf curling, yellowing and vein clearing, and size reduction in leaves. Almost all plants in the surveyed landscape showed high infestation of Bemisia tabaci and symptoms that suggested infection with a begomovirus. Six symptomatic samples were collected from three different sites. All symptomatic samples were found PCR-positive with diagnostic primers for begomovirus (3) when DNA extracted from infected leaves was used as template. Nucleic acids extracted from the symptomatic leaves were used to amplify circular DNA molecules by rolling circle amplification method. The amplified concatameric products were digested with restriction enzyme PstI, which yielded a product ∼2.8 kb in size. The putative begomovirus fragment was cloned and sequenced in both orientations. Partial sequences of six clones were 99 to 100% similar and thus only two clones, PT-2 and PT-3, were fully sequenced. The whole genomes of both clones were 2,761 bp, and both were deposited in GenBank under accession numbers HF968755 and HF968756 for the isolates PT-2 and PT-3, respectively. Both sequences had six open reading frames; Rep, TrAP, REn, and C4 genes in complementary sense; and CP and V2 genes in virion-sense, typical of the begomovirus genome organization. Upon alignment, the two sequences showed 99.4% nucleotide identity with each other, thus representing isolates of a single begomovirus species. BlastN comparison showed PT-2 and PT-3 from petunia were 94 to 95% identical to the sequences of ChCLV from Oman (JN604490 to JN604500), which were obtained from other hosts. ClustalV multiple sequence alignment showed that isolates PT-2 and PT-3 shared maximum sequence identity of 93.3 and 92.8%, respectively, with an isolate of ChLCV-OM (JN604495). According to ICTV rules for begomoviruses, PT-3 should be considered to be a new strain of ChLCV-OM and PT-2 a variant of the already existing ChLCV-OM strain. We propose the name for this new strain as the "Petunia strain" of Chili leaf curl virus (ChLCV-Pet). Two infectious clones were constructed from the PT-2 and PT-3 sequences, clones as 1.75-genome sequences in a binary vector, suitable for agroinfection to confirm their infectivity. Both clones, PT-2 and PT-3, produced typical leaf curl disease symptoms upon inoculation on petunia 18 days post inoculation. The presence of the same virus in symptomatic field infected and inoculated petunia was confirmed by Southern blot using 650 bp DIG labeled probe prepared from CP region of PT-3 isolate. ChLCV-OM, a monopartite begomovirus, is widely associated with leaf curl disease of tomato and pepper in Oman, with its origin traced to the Indian subcontinent (2). Identification of a new strain of ChLCV from petunia provides evidence of an ongoing rapid evolution of begomoviruses in this region. Although petunia has been tested as an experimental host for some begomoviruses (1,4), this is the first report of petunia as natural host for ChLCV, a begomovirus previously reported in tomato and pepper in Oman. References: (1) Cui et al. J. Virol. 78:13966, 2004. (2) Khan et al. Virus Res. 177:87, 2013. (3) Khan et al. Plant Dis. 97:1396, 2013. (4) Urbino et al. Arch. Virol. 149:417, 2003.

Identification of Cotton leaf curl Gezira virus in Papaya in Oman.

Papaya is an important fruit crop in Oman covering some 130 ha with an annual production of 20 tonnes. In 2011, during surveys of farms in the Quriyat region of Oman, papaya plants were found severely affected by leaf curl disease. Leaves with severe curling, vein darkening, and vein thickening were collected for study. Disease incidence ranged from 30 to 50%, particularly in fields with young papaya. A begomovirus (family Geminiviridae) was suspected as the causal agent based on symptoms (1) and the presence of whiteflies in the field. Samples (four to five) were collected from three farms. Total nucleic acids extracted from symptomatic leaves using the CTAB method were used as templates to amplify circular DNAs using Φ29 DNA polymerase and products were digested with restriction enzymes to identify fragments of 2.6 to 2.8 kb typical of geminiviruses. PstI yielded a fragment of ~1.8 kb when the digested product was analyzed by electrophoresis on a 1% agarose gel. The fragment was cloned and sequenced using primer walking strategy in both directions. The sequencing confirmed the exact size (1,764 bp) and the sequence was deposited in GenBank (HE800524). The viral sequence from Oman (isolate Pap-2) showed four open reading frames (ORFs) in the complementary sense (replication associated protein [Rep] gene, the C2 gene, the replication enhancer protein [REn] gene, and the C4 gene) and the virion-sense ORFs (V1 and V2) were missing in the sequence. An initial comparison to NCBI database sequences using BLAST showed the clone from Oman had the highest level of sequence identity to Cotton leaf curl Gezira virus (CLCuGeV) (FJ868828) cloned from okra in Sudan. Subsequent pair wise sequence comparison was done using ClustalV algorithm. Full length sequences of CLCuGeV from database were trimmed according to the size and genomic coordinates of Pap-2 isolate. The Pap-2 isolate sequence was found to have 83.3 to 95.1% sequence identity to CLCuGeV sequences with maximum value to the Sudan isolate. Amino acid sequence comparison showed that the four predicted proteins (Rep, C2, REn, and C4) encoded by the Pap-2 isolate shared 95.3%, 97.8%, 97.7%, and 87.6% sequence identity, respectively, with the homologous proteins of CLCuGeV-SD (FJ868828). The absence of virion-sense protein sequences indicated it to be a subgenomic molecule of CLCuGeV. According to the recommendations of International Committee on Taxonomy of Viruses, these results indicate that the virus identified in association with papaya leaf curl disease in Oman is a variant of CLCuGeV. CLCuGeV is a begomovirus of African origin which is distinct from the begomoviruses of the Middle East and Asia. To our knowledge, this is the first report of CLCuGeV, or any other cotton infecting begomovirus, from papaya in Oman. The presence of a recombinant fragment of CLCuGeV in a Tomato yellow leaf curl virus isolate from Iran (2), and the association of CLCuGeV with cotton in Pakistan (3) and hollyhock in Jordan (GU945265) suggests this virus has moved into the Middle East and Asia from Africa. The identification of CLCuGeV in Oman shows the widespread occurrence of this virus species. This discovery is important since Oman, and other countries in the area, are a hub of international trade and travel, particularly by air and sea, meaning that the virus could spread further. References: (1) R. W. Briddon and P. G. Markham. Virus Res. 71:151, 2000. (2) P. Lefeuvre et al. PLoS Pathog. 6:e1001164, 2010. (3) M. N. Tahir et al. PLoS ONE 6:e20366, 2011.