Detection and molecular characterization of Egyptian isolates of grapevine viruses.

Selected commercial and/or local vineyards and nurseries in three different governorates of Egypt (Alexandria, El-Beheira and El-Menofia) were surveyed for symptoms indicative of infection by grapevine viruses. Leaf samples from red-fruited and white-fruited Vitis vinefera were tested for grapevine leafroll associated viruses (GLRaV-1, GLRaV-2, and GLRaV-3), grapevine viruses A and B (GVA, GVB), grapevine rupestris stem pitting virus (GRSPaV), grapevine fanleaf virus (GFLV), and grapevine fleck virus (GFKV) from early April to late October 2010. Incidence of these viruses was assessed by RT-PCR in 60 different samples. Selected amplicons were sequenced. While GVA was the most wide spread (30%), GLRaV-1, GVB, GFLV, and GFKV were not detected during the survey. However, GVA, GLRaV-2, GLRaV-3, and GRSPaV were detected in the form of single infection or in mixed infections of 2 to 4 viruses. Phylogenetic analysis was performed on all Egyptian isolates of GLRaV-2 (4), GLRaV-3 (7), GVA (3), and GRSPaV (6). GRSPaV was detected for the first time in Egypt. Phylogenetic analysis provided insights into the evolutionary relationship between the reported Egyptian isolates and other previously reported isolates.

First Report of Apple chlorotic leaf spot virus, Cherry green ring mottle virus, and Cherry necrotic rusty mottle virus on Peach in Montenegro.

The sanitary status of peach fruit trees was assessed in central and coastal regions of Montenegro during a survey in September and October of 2011 and 2012. Leaf samples were collected from 58 (2011) and 47 (2012) trees showing chlorotic rings and spots, mosaic, necrosis, leaf distortion, and stunting. Total RNAs was extracted from each sample by RNeasy Plant Mini kit (Qiagen, Germany) and used as a template in PDO (polyvalent degenerate oligonucleotides) nested reverse transcription (RT)-PCR for the detection of fruit tree viruses belonging to the genera Trichovirus, Capillovirus, and Foveavirus (family Betaflexiviridae). PDO primer sets PDO-F1i/PDO-R3i/PDO-R4i and PDO-F2i/PDO-R1i (2) were used in the first RT-PCR and nested PCR, respectively. Total RNAs obtained from Italian Apple chlorotic leaf spot virus (ACLSV)-infected isolate and healthy peach leaves were used as positive and negative controls, respectively. A nested set of primers amplified a 362-bp product from 6 samples collected in 2011 (10.3%) and 13 samples collected in 2012 (27.7%). Sequence analysis included three isolates (367/11, 133/12, and 168/12) chosen from different peach cultivars (Ritastar, Spring Belle, and Redhaven, respectively). Amplified products of expected size of the partial RNA-dependent RNA polymerase from three positive samples were cloned into p-GEM-T Easy Vector (Promega, Madison, WI) and sequenced (MWG-Biotech AG, Germany). Sequences were deposited in GenBank under accession nos. KF534757, KF534769, and KF534766, respectively. BLAST analysis showed that the sequence of isolate 367/11 (KF534757) shared high nucleotide similarity (78.9 to 87.2%) with ACLSV isolates from GenBank, showing highest identity with isolate PBM1 (AJ243438) from Germany. Sequence analysis of isolate 133/12 (KF534769) proved that it is 90.5 to 93.3% identical to Cherry green ring mottle virus (CGRMV) isolates reported from other parts of the world. In particular, the highest nucleotide similarity was showed with isolate P1C124 (AJ291761) from France. Finally, analysis of sequence from the isolate 168/12 (KF534766) revealed high degree of identity (86.1 to 96.1%) with the corresponding nucleotide sequences of the Cherry necrotic rusty mottle virus (CNRMV) isolates, showing highest similarity with isolate 120/86 (AF237816) from Switzerland. To confirm virus infectivity, according to the FAO/IPGRI Technical Guidelines (1), budwood from 367/11, 133/12, and 168/12 samples were grafted into seedlings of peach (GF305), Prunus serrulata (cv. Shirofugen) and P. avium (cv. Sam) then maintained in a greenhouse with controlled conditions. Six months post inoculation, GF305 indexed with 367/11 sample reacts with a green depressed mottle on leaves typical of ACLSV infection. Cherry tree of cv. Shirofugen indexed with sample 133/12 showed symptoms attributable to CGRMV such as epinasty, twisting and curling of leaves while a tree of cv. Sam indexed with 168/12 sample exhibited classical necrotic shot holes in leaves induced by CNRMV infection (1). Sequence analysis of PCR products obtained from indicator plants by RT-PCR as described above showed full nucleotide identity with KF534757, KF534769, and KF534766 sequences and confirmed the presence of previous described viral agents. To our knowledge, this is the first report of ACLSV, CGRMV, and CNRMV occurrence on peach in Montenegro. Due to the economic importance of this crop, sanitation measures should be adopted to improve the control of imported plants and the use of virus-tested propagation material in order to prevent spreading of these viruses. References: (1) M. Diekmann and C. A. J. Putter. FAO/IPGRI Technical Guidelines for the Safe Movement of Germplasm. No. 16. Stone Fruits, 1996. (2) X. Foissac et al. Phytopathology 95:617, 2005.

First Report of Prune dwarf virus and Prunus necrotic ringspot virus on Peach in Montenegro.

In September and October 2011, samples were collected from mature peach trees (~17 years old) exhibiting symptoms of chlorotic rings and spots, vein clearing, mosaic, necrosis, leaf distortion, stunting, and rosette formation in a major commercial orchard (~80 ha) near Podgorica, Montenegro. Samples were collected from nine different peach varieties (cvs. Adriana, Caldesi, Gloria, Maria Marta, May Crest, Morsiani, Rita Star, Spring Belle, and Spring Crest). Samples (n = 58) were tested using DAS-ELISA for the presence of Prune dwarf virus (PDV) and Prunus necrotic ringspot virus (PNRSV). Commercial positive and negative controls were included in each ELISA (antisera and controls supplied by BIOREBA AG, Reinach, Switzerland). Only one symptomatic sample from cv. Gloria tested positive for PDV (sample reference: 399/11), a further 11 samples (cvs. Rita Star [six], May Crest [four] and Spring Crest [one]) were positive for PNRSV. Samples were also tested for Plum pox virus (PPV) by real-time RT-PCR (1). The PDV positive sample (399/11) showing mosaic was in mixed infection with PPV, as were 6 of the 11 PNRSV samples, including sample 373/11 with yellow mottling and leaf distortion symptoms. On single-infected PNRSV, sample 368/11 chlorotic line patterns and leaf deformations were observed. To confirm the presence of PDV and PNRSV, positive samples were also tested by RT-PCR. Total RNA was extracted using RNeasy Plant Mini kit (Qiagen, Hilden, Germany). RT-PCR was performed with primer pairs PDV2F/PDV1R (3) and MG1/MG2 (2) specific for PDV and PNRSV, respectively. Amplicons of the expected size, 173 bp for PDV and 675 bp for PNRSV, were obtained from corresponding ELISA-positive samples. Amplified products from three samples (PDV 399/11 and PNRSV 368/11 and 373/11) were cloned into pGEM-T Easy Vector (Promega, Madison, WI) then sent for sequence analysis (MWG-Biotech AG, Edersberg, Germany). Sequence data was compared to sequences published in GenBank. Analysis of sequence obtained from isolate 399/11 (cv. Gloria) corresponded to partial CP gene of PDV, with a high degree of similarity to isolates reported from other parts of the world ranging from 94.2 to 95.9%, showing highest similarity with isolate Ch 137 (L28145). Sequence analyses of CP gene from PNRSV isolates 368/11 (JX569825) and 373/11 (JX569826) proved to be 89.3 to 99.7% identical with corresponding sequences of isolates previously described. In particular, the Montenegrin PNRSV isolates were most closely related to Chilean NctCl.augl isolate from nectarine (EF565253). To demonstrate that the virus was infectious, seedlings of peach cv. GF305 were side grafted with bud-woods from PDV (sample 399/11) and PNRSV-positive samples (samples 368/11 and 373/11) and a healthy control sample. Grafted seedlings were kept in a greenhouse with a under 16-h light regime at 22 to 24°C and observed for symptom development. No symptoms were observed in grafted plants with the healthy control. All plants inoculated with virus-positive samples exhibited stunted vegetation and mild mottle with no difference in symptoms between the two viruses. Indicator plants of peach cv. GF305 inoculated with PPV dual-infected samples (399/11 and 373/11) were subsequently shown to be positive for PPV by real-time RT-PCR. Subsequent DAS-ELISA test on samples from experimentally inoculated trees using specific antisera as described above confirmed PDV and PNRSV infections as expected. These viruses have recently been reported from sour cherry (Prunus cerasus L.) in Serbia (4), ~600 km to the northeast. However, to our knowledge, this is the first report on the occurrence of PDV and PNRSV in Montenegro. References: (1) N. Capote et al. Int. Microbiol. 12:1, 2009. (2) M. Glasa et al. Ann. Appl. Biol. 140:279, 2002. (3) D. R. Parakh et al. Acta Hortic. 386:421, 1996. (4) S. Radicevic et al. Genetika 44:285, 2012.

First Report of Citrus tristeza virus in National Germplasm of Citrus in Afghanistan.

Rejuvenation of the horticulture industry is a government priority in Afghanistan. With that purpose, European Commission-supported programs specifically focus on greater access to improved and appropriate planting materials to increase the quantity and quality of more competitive horticultural products. Establishment of a biotechnology laboratory was considered essential support to horticulture sector development. This laboratory has begun screening the health status of the Afghan Germplasm National Collection to ensure multiplication of not only the best selected varieties or ecotypes but also to avoid reproduction and distribution of virus-infected fruit trees. Symptom inspection and sample collection for viral diseases was carried out in the citrus orchard during survey activity at the National Collection Experimental Farm in Jalalabad (Nangarhar Province). Ninety-nine variety plots (one row of five plants) were inspected visually and samples from two plants for each plot were collected and analyzed by double-antibody sandwich (DAS)-ELISA. Plants showing vein flecking, yellowing, and plant decline symptoms were observed in several plots. Four accessions were found to be infected by Citrus tristeza virus (CTV): kumquat cv. Margarita (isolates J4 and J8), orange cv. Mahali (J61), mandarin group cv. Fruter (J76), and rough lemon cv. Mahali (J101). Identified isolates have been characterized molecularly. A 655-nt fragment, corresponding to the major coat protein gene, has been amplified from all ELISA-positive samples by reverse transcription (RT)-PCR using CTVF (5'-TAATGGACGACGAACAAAGA-3') and CTVR (5'-CCAAGCTGCCTGACATTAGT-3') primers. Sequence analysis revealed high similarity, ranging from 91.1 to 99.8%, within CTV isolates detected in Jalalabad. In accordance with the phylogenetic groups previously defined (page 8 in: Proceedings of the 15th Conference of the International Organization of Citrus Virologists, 2002), nucleotide sequences of Afghan CTV isolates investigated in the current work cluster in Group 1 (J4 and J8), Group 4 (J61 and J76), and Group 5 (J101). In particular, J4 and J8 isolates show, respectively, identity of 99.4 and 99.2% with reference isolate T36 (GenBank Accession No. M76485) from the United States (Florida). Moreover, in Group 4, isolate J61 and J76 were more similar to ANO-1 isolate (GenBank Accession No. DQ211658) from Egypt (identity of 98.5 and 98.0%, respectively) than to isolate 443-4 (GenBank Accession No. AY791844) from Croatia (97.4 and 97.5%, respectively). Finally, isolate J101 in Group 5, shows identity of 95.6% with isolates C268-2 (GenBank Accession No. AY750770) and C269-6 (GenBank Accession No. AY750775) from Argentina. To our knowledge, our results identified for the first time CTV-infected plants in Afghanistan. The presence of CTV in four accessions of the national citrus collection is of concern for Afghan horticulture. Implementation of the certification schemes is therefore necessary to guarantee the production and the employment of virus-free propagating material.