Investigation of soilborne mosaic virus diseases transmitted by <Emphasis Type="Italic">Polymyxa graminis</Emphasis> in cereal production areas of the Anatolian part of Turkey

Polymyxa graminis is the vector of several important viruses, including Soilborne cereal mosaic virus, Wheat spindle streak mosaic virus, Barley yellow mosaic virus and Barley mild mosaic virus, of winter cereals worldwide. Surveys were carried out to detect these viruses and their vector P. graminis in 300 soil samples from the main wheat and barley production areas of the Anatolian part of Turkey collected in May 2002, June 2004 and May 2005. For these surveys, various susceptible wheat and barley cultivars were pot grown in the collected soil samples in a greenhouse and then analysed using ELISA and RT-PCR to detect the presence of different virus species. In addition, a combination of light microscopy following roots staining with acid fuchsin and PCR was used for detection of P. graminis. All soil samples analysed were found to be free of these soilborne viruses and their vector.     

Occurrence and incidence of viruses infecting green beans in south-eastern Spain

A study was conducted to determine the identity and prevalence of viruses in 455 greenhouses in the main Spanish green bean growing area. Directed surveys were conducted in 422 crops from 2000–2004 to collect samples from diseased plants displaying symptoms that could be attributed to viruses. The samples were analysed to detect any virus by means of dsRNA extraction, mechanical inoculation to test plants, as well as ELISA and/or RT-PCR tests to detect potyviruses, geminiviruses and viruses previously known to infect beans in Spain. Random surveys were conducted in the years 2002 and 2005 (in 21 and 12 greenhouses, respectively) to study the actual incidence of known viruses in the area. Symptoms were recorded in 23,108 plants from which 664 plants were collected and analysed by ELISA or RT-PCR. The results of the directed surveys showed that all the analyzed crops carried the cryptic virus Phaseolus vulgaris endornavirus (PVuV), whereas phytopathogenic viruses appeared in smaller percentages of the crops: Tomato yellow leaf curl virus (TYLCV) 20.4%, Southern bean mosaic virus (SBMV) 9.0%, Tomato spotted wilt virus (TSWV) 4.0%, and the new species Bean yellow disorder virus (BnYDV) that broke out in 2004 with occurrence values higher than 34.3% that year. From 2000–2004 an important decrease in TYLCV was observed, along with a slight increase in SBMV and a consistently low occurrence of TSWV. The results of the random surveys confirmed the increased occurrence of virus detected during the directed surveys, and furthermore demonstrated the percentage of incidence for each virus.     

进境欧洲水仙种球上病毒的检测与鉴定

为明确2013年福建口岸截获的进境欧洲水仙种球上携带的病毒种类,应用血清学、电镜观察和分子生物学检测方法对其可能携带的病毒进行了检测与鉴定。结果显示,水仙花叶病毒(Narcissus mosaic virus,NMV)、水仙黄条病毒(Narcissus yellow stripe virus,NYSV)、水仙潜隐病毒(Narcissus latent virus,NLV)、水仙迟季黄化病毒(Narcissus late season yellows virus,NLSYV)和南芥菜花叶病毒(Arabis mosaic virus,ArMV)5种病毒为阳性,其中NLSYV、ArMV为强阳性;NMV、NYSV、NLV和NLSYV为阳性的样品中含有大小约500~750 nm×12 nm的线状病毒粒体,ArMV为阳性的样品中含有直径约30 nm的球状病毒粒体;经序列测定和分析,扩增到的目的片段大小与各病毒预期扩增片段大小一致,并与已报道的各病毒序列高度同源;病毒复合侵染检测结果显示,该批水仙种球39.7%的样品存在2种以上病毒复合侵染。研究表明,该批进境欧洲水仙种球上携带有NMV、NYSV、NLV、NLSYV和ArMV,且复合侵染现象明显。     

Diversity of European begomoviruses: identification of a new disease complex*

The diversity of whitefly‐transmitted begomoviruses in Europe is low, most being exotic, introduced species. The only agriculturally important viruses are two species causing tomato yellow leaf curl. These viruses are believed to have originated in the Middle East but have since spread right across the Mediterranean region. Two ornamentals (Abutilon and Lonicera japonica) were introduced into Europe from the New World and the Far East, respectively, for the striking symptoms induced by the viruses which infect them. The virus infecting honeysuckle (Honeysuckle yellow vein mosaic virus) has been shown to be part of newly identified cluster of begomoviruses which require an additional component, a satellite molecule termed DNA β, to induce symptoms in their host plants. A further begomovirus, Ipomoea yellow vein virus, which infects the weed Ipomoea indica, is present in the Mediterranean region. The precise origin and relationship of this virus to other begomoviruses is unclear.     

Characterization of a begomovirus causing horsegram yellow mosaic disease in India

The virus causing horsegram (Macrotyloma uniflorum) yellow mosaic disease has been shown to be a typical Old World bipartite begomovirus. The viral origin of the disease has been established through agroinoculation of horsegram using partial tandem repeat clones of both DNA-A and DNA-B. The DNA-A genome shows less than 89% identity with the corresponding sequences of all the begomoviruses in the databases earlier to this sequence submission (AJ627904). Therefore Horsegram yellow mosaic virus (HgYMV-[IN:Coi]) can be considered to be a new species of the genus Begomovirus (family Geminiviridae). Phylogenetic analysis shows that this virus is part of the cluster of mungbean yellow mosaic viruses of legumes from South and South East Asia.     

Incidence of viruses in <Emphasis Type="Italic">Alstroemeria</Emphasis> plants cultivated in Japan and characterization of <Emphasis Type="Italic">Broad bean wilt virus-2, Cucumber mosaic virus</Emphasis> and <Emphasis Type="Italic">Youcai mosaic virus</Emphasis>

Alstroemeria plants were surveyed for viruses in Japan from 2002 to 2004. Seventy-two Alstroemeria plants were collected from Aichi, Nagano, and Hokkaido prefectures and 54.2% were infected with some species of virus. The predominant virus was Alstroemeria mosaic virus, followed by Tomato spotted wilt virus, Youcai mosaic virus (YoMV), Cucumber mosaic virus (CMV), Alstroemeria virus X and Broad bean wilt virus-2 (BBWV-2). On the basis of nucleotide sequence of the coat protein genes, all four CMV isolates belong to subgroup IA. CMV isolates induced mosaic and/or necrosis on Alstroemeria. YoMV and BBWV-2 were newly identified by traits such as host range, particle morphology, and nucleotide sequence as viruses infecting Alstroemeria. A BBWV-2 isolate also induced mosaic symptoms on Alstroemeria seedlings.     

Common reed (Phragmites communis) is a natural host of important cereal viruses in the Trakya region of Turkey

Common reed (Phragmites communis Trin.), a perennial grass, is a widespread weed in the Trakya region of Turkey. Reed leaf samples were collected in 2004 and 2005, and tested for the presence of theMaize dwarf mosaic virus (MDMV),Sugarcane mosaic virus (SCMV),Barley yellow dwarf virus-PAV (BYDV-PAV),Cereal yellow dwarf virus-RPV (CYDV-RPV) andWheat dwarf virus (WDV) by DAS-ELISA, PTA-ELISA and Western blot analysis. MDMV was identified in five out of sixP. communis samples that exhibited characteristic virus-like symptoms in 2004. The remaining sample was co-infected with MDMV and BYDV-PAV. Transmission electron microscopy confirmed the presence of flexuous rod-shaped virus particles in four samples that reacted positively for MDMV in ELISA. In 2005, ELISA revealed that nine out of 234 samples that were collected in two different locations were infected with MDMV, nine with SCMV, and three with BYDV-PAV. No sample contained CYDV-RPV, JGMV and WDV. Our results confirm that the common reed is a host of BYDV-PAV and indicate, for the first time, that it is also a natural host of MDMV and SCMV.P. communis most likely acts as a reservoir of these three viruses in the Trakya region in Turkey. http//www.phytoparasitica.org posting Sept. 13, 2006.     

Molecular epidemiology of cassava mosaic disease in Madagascar

Cassava is the staple food for hundreds of millions of people in Africa but its cultivation is seriously constrained by cassava mosaic disease (CMD) in Madagascar, and in Africa in general. This study identified the cassava mosaic geminiviruses (CMGs) involved in CMD in Madagascar and their associated epidemiological characteristics from countrywide surveys. Molecular characterization of CMGs in Madagascar revealed an unprecedented diversity and co‐occurrence of six viruses: African cassava mosaic virus (ACMV), East African cassava mosaic Cameroon virus (EACMCV), East African cassava mosaic Kenya virus (EACMKV), East African cassava mosaic virus (EACMV), South African cassava mosaic virus (SACMV) and the recently described Cassava mosaic Madagascar virus (CMMGV). Distinct geographical distributions were observed for the six viruses. While ACMV was more prevalent in the central highlands, EACMV and EACMKV were prevalent in lowlands and coastal regions. Both EACMCV and SACMV occurred in almost all the localities visited. PCR diagnosis revealed that mixed infection (up to four co‐infected viruses) occurred in 21% of the samples and were associated with higher symptom severity scores. Pairwise comparisons of virus associations showed that EACMCV was found in mixed infections more often than expected while ACMV and SACMV were mostly found in single infections. A greater abundance of whiteflies was observed in lowland and coastal areas. Nevertheless, infected cuttings remain the primary source of CMD propagation (95%) in Madagascar.     

Viruses affecting tomato crops in Serbia

In a two-year survey (2011–2012), 3220 samples were collected and analyzed in order to determine the presence and distribution of viruses in tomato crops at 56 localities of 18 districts in Serbia. Out of 12 viruses tested, Cucumber mosaic virus (CMV), Potato virus Y (PVY), Alfalfa mosaic virus (AMV), Tomato spotted wilt virus (TSWV), Tomato mosaic virus (ToMV) and Tobacco mosaic virus (TMV) were detected in 42.1, 40, 11, 8.6, 2.3 and 1.3% of the total tested samples, respectively. The results revealed that CMV was prevalent in 2011 and PVY in 2012. CMV and PVY, apart from being predominant, were also the most widespread viruses. In general, single infections were the most frequent type of infection. Additionally, the most common mixed infections were double infections and the most prevalent combination was CMV and PVY. In 2011, the incidence of diseases and the percentage of all infection types were significantly higher than in 2012. Furthermore, in 2011, regardless of total single infections being prevalent compared to mixed infections, two prevailing viruses were commonly detected in mixed infections. The additional molecular testing of ELISA-negative samples using virus specific primers did not reveal the presence of Pepino mosaic virus (PepMV), Tomato yellow leaf curl virus (TYLC), Tomato infections chlorosis virus (TICV) and Tomato chlorosis virus (ToCV).     

Occurrence of viruses in field-grown pepper crops and some of their reservoir weed hosts in Samsun, Turkey

Pepper production is affected by several viral diseases in Samsun, Turkey. To determine the identity of these viruses, a total of 313 samples from field-grown peppers were collected during surveys in 1998 and 1999, and tested by enzyme linked immunosorbent assay (ELISA). Six viruses,Alfalfa mosaic virus (AMV),Cucumber mosaic virus (CMV),Potato virus Y (PVY),Tomato mosaic virus (ToMV),Tobacco mosaic virus (TMV) andTomato spotted wilt virus (TSWV) were detected in the samples. Of 313 plants tested, 42 were doubly infected, and TMV+PVY (15.4%) was the most common double infection. This is also the first report of AMV in pepper fields in Turkey. The effect of some weed species that may act as reservoir of these viruses was also investigated in the region and of 24 weed species belonging to 15 families tested, 16 were found to be infected with at least one virus.Amaranthus retroflexus (Redroot pigweed) appeared to be a common host of CMV, PVY, ToMV, TMV and TSWV, whereasHibiscus trionum (Venice mallow) was recorded as a new weed host of PVY and TSWV. The majority of weed species found to be virus infected were very common in the pepper growing areas of the region. This indicates that pepper fields contaminated with these weeds are under risk of viral infections. http://www.phytoparasitica.org posting July 21, 2005.     

Unterschiedliche Formen der Resistenz gegen bodenbürtige Viren des Weizens

In Germany the furovirus Soil-borne cereal mosaic virus (SBCMV) and the bymovirus Wheat spindle streak mosaic virus (WSSMV) occur often together particularly in several rye production areas. Soil-borne wheat mosaic virus (SBWMV), a wheat infecting furovirus, has so far been found only in one field near Heidelberg. Each of these viruses is transmitted by Polymyxa graminis. The cultivation of resistant varieties is the only promising measure to prevent yield losses caused by soil-borne viruses. Resistance of wheat against the bymovirus WSSMV is comparable to the immunity of barley to the bymoviruses Barley yellow mosaic virus and Barley mild mosaic virus. In case of immunity no virus multiplication is observed in resistant cultivars. In contrast, all wheat cultivars are hosts of the furoviruses. All cultivars – including the resistant ones – can be infected following mechanical inoculation with SBWMV and SBCMV. Resistance to furoviruses is based on reduced levels of virus multiplication in roots and on inhibition of virus movement from roots to leaves. Because of the inhibited virus movement from roots to aerial parts of plants this type of resistance is referred to as translocation resistance. In spite of the different resistance mechanisms the absence of virus symptoms on the leaves is a common selection criterion for both immunity and translocation resistance. Therefore, the symptom free development of plants on uniformly infested fields is the best criterion for selecting wheat lines with resistance to soil-borne viruses. The limited suitability of other selection methods is discussed.     

Using high-throughput sequencing in support of a plant health outbreak reveals novel viruses in Ullucus tuberosus (Basellaceae)

Ullucus tuberosus (ulluco) is a tuber-forming species that has become a novel crop in highland and temperate maritime climates. Eight viruses have been previously reported infecting Ullucus, including Andean potato latent virus (APLV), a quarantine virus within the European Union. No reference sequences have been published for the viruses previously described from U. tuberosus. Plants grown in the UK for the internet trade were tested for the presence of quarantine viruses using ELISA and real-time RT-PCR. ELISA positive results were obtained for APLV and multiple other viruses. A similar suite of viruses was detected at a second outbreak site linked to horticultural trade. Virus identification was by high-throughput sequencing (HTS) using a ribosomal RNA (rRNA)-depleted total RNA approach. Analysis of viral contigs indicated the presence of several novel viruses closely related to, but not consistent with, the viruses indicated by ELISA. Further confirmatory testing by real-time RT-PCR indicated that two tymoviruses, tentatively named Ullucus tymovirus 1 and Ullucus tymovirus 2, were more closely related to each other (85% identity), than to APLV or Andean potato mild mosaic virus (63–66% identity). APLV could not be confirmed from either site by either HTS or PCR. A novel tobamovirus (Ullucus tobamovirus 1) was only detected at the initial outbreak site. A novel polerovirus (Ullucus polerovirus 1) and a distinct genotype of Papaya mosaic virus were detected from both outbreak sites. Deploying HTS during a plant health outbreak demonstrates the potential of this approach to give rapid, accurate diagnosis.     

Occurrence and distribution of viruses infecting tomato and pepper in Alibori in northern Benin

In surveys conducted in 2011 and 2012 to identify the viruses causing diseases on pepper and tomato in the department of Alibori in northern Benin, 451 samples of pepper and tomato were analyzed by ELISA using 11 specific antibodies. The highest virus incidence among the surveyed districts was recorded on pepper in Malanville (56.18%), followed by Karimama (39.32%). The most frequently found viruses were Pepper veinal mottle virus (PVMV), Cucumber mosaic virus (CMV), and Potato virus Y-necrotic (PVY-n), accounting respectively for 22.39%, 21.73% and 15.96% of the collected samples. Tomato yellow leaf curl virus (TYLCV) was detected in only 2.43% of the samples, whereas Alfalfa mosaic virus (AMV), Chilli veinal mottle virus (ChiVMV), Tomato mosaic virus (ToMV) and Tomato spotted wilt virus (TSWV) were not detected in any of the samples tested. Double and triple infections involving different virus combinations were found, respectively, in 14.86% and 4% of the samples. Five plant species (Euphorbia hirta Linnaeus, Moringa oleifera Lam, Leucas martinicencis (Jacquin) R. Brown, Combretum micranthum G. Don, Abelmoschus esculentus L. Moench.) out of 30 samples belonging to 13 botanical families, collected within or nearby tomato and pepper fields, were found infected with PVMV, PVY-n, and CMV. Control measures to reduce the impact of viruses on pepper and tomato production are discussed. This is the first report of viruses infecting pepper and tomato in Benin.