Principal maize viruses in Mediterranean countries

Maize plants with virus-like symptoms were sampled in fields in Greece, Yugoslavia and Italy in 1994. Disease incidence (%) and disease severity (1-6) were assessed. Leaf samples were tested by enzyme-linked immunosorbent assay (ELISA) and electroblot immunoassay (EBIA). Antisera against maize dwarf mosaic virus (MDMV), sugarcane mosaic virus (SCMV) and barley yellow dwarf viruses (BYDVs) (PAV- and RPV-like) were used in these tests. A higher disease incidence occurred in Italy and Greece than in Yugoslavia. MDMV was proved by both ELISA and EBIA in all maize genotypes in Greece, Yugoslavia and Italy. None of the samples reacted with SCMV antibodies. A total of 13.7 and 11% of individual Greek samples were positive for PAV- and RPV- respectively, while, 17.5 and 5% of Yugoslav samples were positive for PAV- and RPV- respectively. Phragmites sp, a perennial maize weed, was also positive for PAV- and RPV- by ELISA

Identifikacija virusa infektivnih za običnu tikvu (Cucurbita pepo L.) u Jugoslaviji

This study was carried out in order to identify the major viruses infecting pumpkins (Cucurbita pepo)grown in Serbia. Leaf samples from virus-infected pumpkin plants were collected in mid-July 2001. Naked-seeded and hulled oil pumpkins, patty pan, zucchini and summer squash from three different locations were included (Table 1). Virus-infected plants showed different symptoms (Table 2 and Figures 1-4). Due to the great variability of the symptoms, the causal viruses could not be fully and precisely determined by visual examination only. The infected samples were tested by the biotest, as well as by two serological methods, ELISA and EBIA. Polyclonal antibodies raised against cucumber mosaic cucumovirus (CMV), zucchini yellow mosaic potyvirus (ZYMV), watermelon mosaic potyvirus 1 (WMV-1), watermelon mosaic potyvirus 2 (WMV-2) and squash mosaic comovirus (SqMV) were used. In each of the 50 collected samples one or two viruses were detected (Tables 3 and 4). The most prevalent viruses infecting pumpkins were ZYMV (62%) and CMV (58%). WMV-2 was extremely rare.Cilj ovih istraživanja bio je da se identifikuju najvažniji virusi tikava (Cucurbita pepo L) gajenih u Srbiji. Uzorci biljnog materijala uljane tikve-golice, uljane tikve sa ljuskom, tikvice za jelo, patisona i cukinija koji su bili zaraženi virusima, sakupljeni su u tri lokaliteta sredinom jula 2001. godine (tab. 1). Biljke zaražene virusima pokazivale su različite simptome (tab. 2 i sl. 1-4). Tačna determinacija virusa samo na osnovu simptoma nije moguća zbog varijabilnosti samih simptoma. Zaraženi uzorci su testirani biotestom kao i primenom dve serološke metode, ELISA i EBIA korišćenjem poliklonalnih antitela na Cucumber mosaic cucomovirus (CMV) Zucchini yellow mosaic potyvirus (ZYMV), Watermelon mosaic potyvirus 2 (WMV-2), Watermelon mosaic potyvirus 1 (WMV-1) i Squash mosaic comovirus (SqMV). U 50 ispitanih uzoraka detektovan je jedan ili dva virusa (tab. 3 i 4). Preovlađujući virusi tikava bili su ZYMV (62%) i CMV (58%). WMV-2 je detektovan u veoma malom broju uzoraka

Biološka i serološka karakterizacija virusa tikvica u Jugoslaviji

A survey on summer squash open field crops was carried out during 2000 and 2001 in order to identify the major viruses infecting these crops in different localities. Plants showed different types of symptoms: mild mosaic, chlorotic spotting, distinctive mosaic, blistering of leaf lamina leaf yellowing, deformation of leaf lamina, knobbed fruits and stunting of plants. The symptoms were very variable but showed the viral nature of the investigated summer squash diseases. The collected samples were tested by bioassay and by two serological methods ELISA and EBIA using cucumber mosaic cucumovirus (CMV), zucchini yellow mosaic potyvirus (ZYMV), watermelon mosaic potyvirus 2 (WMV-2), zucchini yellow flack potyvirus (ZYFV) watermelon mosaic potyvirus 1 (WMV-1), squash mosaic comovirus (SqMV) and cucurbit aphid-borne yellows polerovirus (CABYV) polyclonal antisera. In all tested samples single or mixed infection with ZYMV, CMV and WMV-2 was detected. The most prevalent virus infecting summer squash was ZYMV. This is the first report of ZYMV, the most destructive virus infecting cucurbits, in Yugoslavia. It was also proven that the identified viruses are transmissible by Aphis gossypii in a non-persistent manner, but possible role of seed in virus transmission was not confirmed.U toku 2000. i 2001. godine izvršen je pregled useva tikvica za jelo da bi se identifikovali osnovni virusi infektivni za tikvice u različitim lokalitetima. Biljke su pokazivale različite simptome: blagi mozaik hlorotičnu pegavost, izraženi mozaik, klobučavost liske, žućenje lista deformacije liske, bradavičaste izraštaje na plodu i kržljavost biljaka. Simptomi su veoma varijabilni i na osnovu njih se ne može obaviti determinacija virusa prouzrokovača oboljenja. Sakupljeni uzorci su testirani biotestom, kao i sa dve serološke metode, ELISA i EBIA korišćenjem poliklonalnih antiseruma na cucumber mosaic cucumovirus (CMV), zucchini yellow mosaic potyvirus (ZYMV), watermelon mosaic potyvirus 2 (WMV-2) zucchini yellow flack potyvirus (ZYFV), watermelon mosaic potyvirus 1 (WMV-1), squash mosaic comovirus (SqMV) i cucurbit aphid-borne yellows polerovirus (CABYV). U svim ispitivanim uzorcima dokazana je pojedinačna ili mešana infekcija sa ZYMV, WMV-2 i CMV. Najčešće infekcije su bile sa ZYMV. Ovaj virus, jedan od najdestruktivnijih virusa na vrežastim kulturama, prvi put je konstatovan u našoj zemlji. Takođe je utvrđeno da se identifikovani virusi prenose na neperzistentan način vašima Aphis gossypii, a moguća uloga semena u pojavi oboljenja nije potvrđena

Incidence of viruses infecting spinach in Greece, highlighting the importance of weeds as reservoir hosts

The aim of this survey was to identify viruses infecting spinach (Spinacia oleracea L.) in the most important spinach-producing areas in Greece. A total of 1074 spinach samples were collected from eleven districts belonging to the prefectures of Thessaloniki, Chalkidiki and Imathia in northern Greece, and Evia in central Greece. Samples were tested by ELISA, mechanical inoculation onto indicator plants and immunoelectron microscopy. Beet western yellows virus (BWYV), Cucumber mosaic virus (CMV) and Turnip mosaic virus (TuMV) were identified in 13.5%, 7% and 5.4% of samples, respectively, infected samples being detected in all regions examined. This is the first record of CMV and TuMV infecting spinach in Greece, and the first report of BWYV occurrence in any crop nationwide. Surveys were also conducted to assess the potential reservoir hosts of BWYV, CMV and TuMV in weeds collected from spinach fields. All three viruses were detected among 125 samples tested by ELISA. TuMV prevailed as it occurred in 14.4% of all weed sample

Elimination of PPV and PNRSV through thermotherapy and meristem-tip culture in nectarine

The plum pox virus (PPV) and prunus necrotic ringspot virus (PNRSV) cause serious disease problems in stone-fruit trees. In this work, the possibility of obtaining plant material free from these viruses through thermotherapy and meristem-tip culture from infected nectarine shoots (Prunus persica var. nectarina Max, cv. ''Arm King'') was studied. In addition, the detection of these viruses in in vitro cultures and young acclimatized plantlets with double antibody sandwich-enzyme-linked immunosorbent assay (DAS-ELISA) and multiplex reverse transcriptase-polymerase chain reaction (RT-PCR) was studied. Meristem-tip explants (0.8–1.3 mm) derived from sprouted buds of winter wood and spring shoots from field grown plants had a 2–5% regeneration response. However, application of thermotherapy to potted nectarine trees (3 weeks at a maximum temperature of 35°C) facilitated excision of longer meristem tips (1.3–2.0 mm) that resulted in a significantly higher regeneration response (38%) in woody plant medium (WPM) without plant growth regulators. Such explants formed multiple shoots with the addition of 8 M benzylaminopurine and 0.8 M indoleacetic acid. When they were tested for the presence of PPV and PNRSV, 86% and 81% were found to be virus-free as detected by DAS-ELISA and multiplex RT-PCR, respectively. Individual shoots excised from virus-free cultures readily rooted in vitro (half-strength WPM plus 2 M indolebutyric acid) and grew to plantlets. The combination of an efficient protocol for virus elimination and the establishment of highly sensitive diagnostics resulted in the production of nectarine plants free from PPV and PNRSV

First report of Tomato yellow leaf curl Sardinia virus (TYLCSV) infecting tomato crops in Greece

Tomato yellow leaf curl virus (TYLCV) and Tomato yellow leaf curl Sardinia virus (TYLCSV) are two viruses of the genus Begomovirus (family Geminiviridae) causing yellow leaf curl disease of tomato ( Lycopersicon esculentum ) crops in the Mediterranean basin (Accotto et al ., 2000) and other regions of the world (Czosneck & Laterrot, 1997). In Greece, tomato yellow leaf curl disease was first reported in 2000, causing heavy losses in greenhouse and open field tomatoes in Crete (Avgelis et al ., 2001). During the summer of 2005, a high percentage of greenhouse tomato crops in southern Peloponnese and Crete exhibited severe stunting, reduced leaf size and curling, yellowing, shortened internodes and a bushy appearance; symptoms that could easily be attributed to tomato yellow leaf curl disease. High populations of the whitefly vector Bemisia tabaci were present in greenhouse and open field tomato crops. Plants with symptoms were collected from the areas of Glykovrysi, Agios Ioannis, Neapoli (Peloponnese) and Mires, Tympaki, Ierapetra (Crete). DNA was extracted from leaves of 48 of these plants and a 580 bp of the coat protein (CP) gene was amplified by polymerase chain reaction (PCR) using the TY(+) and TY(–) primer pair (Accotto et al ., 2000). Restriction fragment length polymorphism (RFLP) analysis (using restriction endonuclease Ava II) of the PCR product produced a 360, 150 and 68 bp pattern from 26 isolates collected from all sampling areas in Peloponnese and from two areas in Crete (Mires, Tympaki), indicating the presence of TYLCSV. All 22 isolates from Ierapetra (Crete) produced a TYLCV pattern (302 and 277 bp). The amplified DNA from six TYLCSV isolates was cloned and sequenced. All six sequences were identical (EMBL accession no. AM 259652) and showed 100% nucleotide identity to a TYLCSV isolate from Sicily (EMBL accession no. Z28390). These results show that both TYLCV and TYLCSV species co-exist in Crete, whereas in Pelloponese only TYLCSV was found. This is the first report of TYLCSV in Greece

First report of Tomato chlorosis virus on tomato crops in Cyprus

In the summer of 2004, yellowing symptoms similar to those caused by nitrogen and/or magnesium deficiency were observed in field- and glasshouse-grown tomatoes ( Lycopersicon esculentum ), in the Parekklisia area of Cyprus. Initially, lower leaves showed extensive interveinal yellowing with necrotic flecks, brittleness and occasional upward leaf rolling, before finally the whole plant turned yellow. Similar symptoms were observed during 2005 in glasshouse tomatoes grown in areas located on the southwest coastal region of the island. The abundance of whiteflies on the affected plants suggested the involvement of the whitefly-transmitted Tomato chlorosis virus (ToCV) and/or Tomato infectious chlorosis virus (TICV), both of the genus Crinivirus (Wisler et al ., 1998). Leaves of 18 affected plants were collected, total RNA was isolated and RT-PCR was performed in a single tube using primers HS-11 and HS-12, followed by a multiplex nested-PCR with primers TIC-3/TIC-4 and ToC- 5/ToC-6, for the detection of TICV and ToCV, respectively (Dovas et al ., 2002). A PCR product of 463 bp, corresponding to the HSP 70 gene of ToCV, was amplified for all tested samples. The sequences of four cloned PCR products were identical (EMBL accession number AM158958) and showed 99% nucleotide identity to a ToCV isolate from Florida (accession number AY903448). ToCV is vectored by Bemisia tabaci ( biotypes A and B ), Trialeurodes vaporariorum and T. abutilonea . Although there have been no systematic studies on whitefly incidence and distribution in Cyprus, it seems that B. tabaci is the predominant species present, as Tomato yellow leaf curl virus (Ioannou, 1985) and Cucurbit yellow stunting disorder virus (Papayiannis et al ., 2005), vectored by this species, are prevalent in tomatoes and cucurbit crops, respectively. On the other hand, the incidence of Beet pseudo-yellows virus (transmitted by T. vaporariorum) is much lower. This is the first report of ToCV in Cyprus

Cydonia japonica, Pyrus calleryana and P. amygdaliformis: three new ornamental or wild hosts of Apple stem pitting virus

Japanese quince, ornamental and wild pear symptomless samples were infected with Apple stem pitting virus (ASPV). Identification of ASPV was achieved by different PCR assays that amplified either the RNA polymerase or coat protein gene regions. For further confirmation, 312 bp amplicons within the polymerase gene were sequenced and compared with previously published ASPV sequences and additional sequences of isolates from ancient Italian cultivars. Comparison of the partial sequences isolated from wild/ornamental hosts and from cultivated species revealed significant divergence levels. Among the wild/ornamental isolates, the PCT88 isolate from Pyrus calleryana was the most divergent, having an amino acid deletion and incorporating a unique stretch of amino acids not present in any other isolate. Further to this preliminary partial sequence data, statistical analysis demonstrated that the isolates from wild or ornamental hosts were not more closely related to each other than to isolates from cultivated hosts. These results represent the first report of natural ASPV infection in these novel ornamental and wild Rosaceae hosts

Identification and Sequence Analysis of a Novel Ilarvirus Infecting Sweet Cherry

In the present study, we utilized high throughput and Sanger sequencing to determine the complete nucleotide sequence of a putative new ilarvirus species infecting sweet cherry, tentatively named prunus virus I (PrVI). The genome of PrVI is comprised of three RNA segments of 3474 nt (RNA1), 2911 nt (RNA2), and 2231 nt (RNA3) and features conserved motifs representative of the genus Ilarvirus. BlastN analysis revealed 68.1–71.9% nt identity of PrVI with strawberry necrotic shock virus (SNSV). In subsequent phylogenetic analysis, PrVI was grouped together with SNSV and blackberry chlorotic ringspot virus (BCRV), both members of subgroup 1 of ilarviruses. In addition, mini-scale surveys in stone fruit orchards revealed the presence of PrVI in a limited number of sweet cherries and in one peach tree. Overall, our data suggest that PrVI is a novel species of the genus Ilarvirus and it consists the fifth member of the genus that is currently known to infect Prunus spp