Soilborne wheat mosaic virus movement protein and RNA and wheat spindle streak mosaic virus coat protein accumulate inside resting spores of their vector, Polymyxa graminis

To study virus-vector interactions between Soilborne wheat mosaic virus (SBWMV) or Wheat spindle streak mosaic virus (WSSMV) and Polymyxa graminis Ledingham, P. graminis was propagated in plants grown hydroponically. P. graminis accumulated to high levels in several barley cultivars tested. Multiple developmental stages of P. graminis could be identified in infected barley roots. Accumulation of SBWMV and WSSMV inside P. graminis sporosori in the roots of soil-grown winter wheat and hydroponically grown barley was compared to determine if data obtained from plants naturally infected plants and plants infected by manual inoculation were similar. WSSMV coat protein (CP), SBWMV RNAs, SBWMV movement protein but not SBWMV CP were detected in both soil-grown winter wheat and hydroponically grown barley roots. These data are the first direct evidence that SBWMV and WSSMV are internalized by P. graminis.     

Sequence analysis of a soilborne wheat mosaic virus isolate from Italy shows that it is the same virus asEuropean wheat mosaic virus andSoilborne rye mosaic virus

The complete sequence of the two RNAs of a furovirus isolate from durum wheat in Italy was determined. Sequence comparisons and phylogenetic analysis were done to compare the Italian virus withSoilborne wheat mosaic virus (SBWMV) from the USA and with furovirus sequences recently published asEuropean wheat mosaic virus (EWMV), from wheat in France, andSoilborne rye mosaic virus (SBRMV), from rye and wheat in Germany. Over the entire genome, the Italian isolate RNA1 and RNA2 had respectively 97.5% and 98.6% nucleotide identity with EWMV, 95.5% and 85.8% with SBRMV-G and 70.6% and 64.5% with SBWMV. The Italian isolate was therefore clearly distinct from SBWMV The European isolates all appear to belong to the same virus and the nameSoilborne cereal mosaic virus may resolve earlier ambiguities.     

Sequence analysis of a soilborne wheat mosaic virus isolate from Italy shows that it is the same virus asEuropean wheat mosaic virus andSoilborne rye mosaic virus

The complete sequence of the two RNAs of a furovirus isolate from durum wheat in Italy was determined. Sequence comparisons and phylogenetic analysis were done to compare the Italian virus withSoilborne wheat mosaic virus (SBWMV) from the USA and with furovirus sequences recently published asEuropean wheat mosaic virus (EWMV), from wheat in France, andSoilborne rye mosaic virus (SBRMV), from rye and wheat in Germany. Over the entire genome, the Italian isolate RNA1 and RNA2 had respectively 97.5% and 98.6% nucleotide identity with EWMV, 95.5% and 85.8% with SBRMV-G and 70.6% and 64.5% with SBWMV. The Italian isolate was therefore clearly distinct from SBWMV The European isolates all appear to belong to the same virus and the nameSoilborne cereal mosaic virus may resolve earlier ambiguities.     

Evidence that soilborne wheat mosaic virus moves long distance through the xylem in wheat

Summary Soilborne wheat mosaic virus (SBWMV) is a member of the genusFurovirus of plant viruses. SBWMV is transmitted to wheat roots by the plasmodiophorid vectorPolymyxa graminis. Experiments were conducted to determine the path for SBWMV transport from roots to leaves. The results of immunogold labeling suggest that SBWMV enters and moves long distance through the xylem. SBWMV may enter primary xylem elements before cell death occurs and then move upward in the plant after the xylem has matured into hollow vessels. There is also evidence for lateral movement between adjacent xylem vessels.Abbreviations SBWMV Soilborne wheat mosaic virus - TMV Tobacco mosaic virus - BMV Brome mosaic virus - PMTV Potato mop-top virus - BNYVV Beet necrotic yellow vein virus - WSSMV Wheat spindle streak mosaic virus - WSMV Wheat streak mosaic virus     

The use of conventional and quantitative real-time PCR assays for Polymyxa graminis to examine host plant resistance, inoculum levels and intraspecific variation

* A real-time PCR protocol based on 18S rDNA sequences was developed to provide a specific, sensitive and quantitative assay for the root-infecting virus vector Polymyxa graminis. * The assay was calibrated with zoospore suspensions and inoculated roots and then shown to work with naturally infected plant roots and infested soil. Both the temperate P. graminis ribotypes previously described are detected but are not distinguished. DNA from related plasmodiophorids and from a range of fungi and plants was not detected. * Different genotypes of Triticum were grown in a soil infested with P. graminis and Soil-borne cereal mosaic virus (SBCMV). The genotypes differed in susceptibility to P. graminis, the least susceptible being the Triticum monococcum accession K-58505. * Conventional PCR assays and sequencing of amplified rDNA fragments showed that P. graminis isolates infecting wheat were mostly, but not exclusively, of ribotype II. Ribotype II was clearly associated with SBCMV transmission and seems to occur preferentially on wheat whereas ribotype I is mostly associated with barley.     

Identification of a Potential Source of Complete Resistance to Soilborne Wheat Mosaic Virus in a Wheat-Thinopyrum Intermedium Addition Line

Soilborne wheat mosaic virus (SBWMV) is a Furovirus transmitted by the plasmodiophoraceous fungus, Polymyxa graminis . Resistant cultivars of wheat (Triticum aestivum) to SBWMV have already been described. The resistance encountered mostly includes root infection without viral migration to foliage. In this study, the reaction of addition lines (L1, LIS, L2, L3, L4, L7), and the partial amphiploid derived from wheat (Vilmornn 27) and Thmopyrum intermedium has been evaluated. Lines L1. L3. L7. L1S and cultivar Vilmorin 27 are susceptible to SBWMV. Lines L4 and TAF 46 are root infected only. Chromosome 4Ag in L4 is thought to have an equivalent reaction to that one found in the mostly encountered resistance. Another type of resistance in a wheat line (1.2) with the added chromosome 3Agi of Th. intermedium has been characterized. In this line, L2, no SBWMV particles were detected on their roots by enzyme-linked immunosorbent assays. Contrary to observations made on lines L1, LIS, L3, L4, L7, amphiploid TAF 46. and the wheat cultivars (Festival. Fandango, Vilmonn 27), no resting spores of P. graminis were found on roots of L2 2 months post inoculation. It is suggested that the disomic addition line L2 is immune to SBWMV.     

山东烟台小麦土传病毒病由小麦黄花叶病毒和土传小麦花叶病毒相关病毒复合侵染所致

在山东省烟台地区的小麦上发生一种由土壤中禾谷多粘菌Polymyxa graminis传播的病毒病,感病小麦植株表现矮化褪绿和花叶症状.我们于1997年4月从病区采集感病小麦植株,进行了病毒种类鉴定.直接电镜观察发现有二种病毒粒子,一种粒子呈棒状,占大多数,其长度约为300nm和150nm; 另一种粒子呈线状,数量较少,长度为500nm～700nm.免疫电镜结果表明,棒状病毒粒子仅与土传小麦花叶病毒(soil-borne wheat mosaic virus, SBWMV)抗血清反应,而不与小麦黄花叶病毒(wheat yellow mosaic virus,WYMV)抗血清和小麦梭条斑花叶病毒(wheat spindle streat mosaic virus,WSSMV)抗血清反应;反之,线状病毒仅与WYMV、WSSMV抗血清反应,而不与SBWMV抗血清反应.用WYMV和SBWMV两种抗血清同时进行修饰时,线状病毒粒子和棒状病毒粒子均发生反应.     

Screening for Barley Yellow Dwarf Luteovirus Resistance in Barley on the Basis of Virus Movement

The movement of barley yellow dwarf luteovirus (BYDV) was evaluated in susceptible and resistant barley and bread wheat genotypes. After leaf inoculation, the virus infected the root system and the growing point of susceptible earlier than resistant, barley genotypes. No difference in virus movement occurred in resistant and susceptible wheat genotypes. It was possible to reliably differentiate susceptible from resistant genotypes when root extracts of 41 barley genotypes were tested by DAS-ELISA 3 or 4 days after inoculation at the oneleaf stage. When barley plants inoculated at the two- or three-leaf stage were assayed by tissue-blot ELISA on nitrocellulose membrane, virus was detected in the phloem vessels of the growing points of the susceptible, but not of the resistant genotype, 4–6 days after inoculation. Our results thus suggest that screening for BYDV resistance in barley could be done quickly and cheaply especially when assays are made by the tissue-blot test.     

Use of Monoclonal Antibodies for the Serological Differentiation of Wheat and Oat Furoviruses

Twenty monoclonal antibodies (MAbs) to Chinese wheat mosaic virus (CWMV) were produced by immunizing BALB/c mice with purified CWMV. These MAbs and polyclonal antisera against CWMV and soil-borne wheat mosaic virus Oklahoma isolate (SBWMV-Okl) were used to differentiate the wheat and oat furoviruses, CWMV, SBWMV, oat golden stripe virus (OGSV) and European wheat mosaic virus (EWMV). Enzyme-linked immunosorbent assays and Western blotting showed that the dominant epitope(s) of CWMV was shared partially with OGSV whereas those of SBWMV were shared with CWMV, OGSV and EWMV in varying degrees. When CWMV virions were briefly digested with trypsin, coat protein fragments of about 12, 10 and 8 kDa were produced and these reacted with the polyclonal antisera and some MAbs, indicating that they contained dominant epitopes of CWMV and SBWMV. Computer analysis of the coat protein sequences suggested that the epitope shared between CWMV and OGSV was located at amino acids 35–40, whereas the dominant epitopes of SBWMV, which were shared with CWMV, EWMV and OGSV, were in the C terminal half of the coat protein     

Sequence analysis of a soil-borne wheat mosaic virus isolate from Italy shows that it is the same virus as European wheat mosaic virus and Soil-borne rye mosaic virus

The complete sequence of the two RNAs of a furovirus isolate from durum wheat in Italy was determined. Sequence comparisons and phylogenetic analysis were done to compare the Italian virus with Soil-borne wheat mosaic virus (SBWMV) from the USA and with furovirus sequences recently published as European wheat mosaic virus (EWMV), from wheat in France, and Soil-borne rye mosaic virus (SBRMV), from rye and wheat in Germany. Over the entire genome, the Italian isolate RNA1 and RNA2 had respectively 97.5% and 98.6% nucleotide identity with EWMV, 95.5% and 85.8% with SBRMV-G and 70.6% and 64.5% with SBWMV. The Italian isolate was therefore clearly distinct from SBWMV. The European isolates all appear to belong to the same virus and the name Soil-borne cereal mosaic virus may resolve earlier ambiguities.     

A conserved locus conditioning Soil-borne wheat mosaic virus resistance on the long arm of chromosome 5D in common wheat

Soil-borne wheat mosaic virus (SBWMV) is considered to be one of the most important diseases in winter wheat regions of the central and southeastern United States. Utilization of resistant cultivars is the most efficient and environmentally friendly means of control. To identify potential quantitative trait loci (QTL) or effective gene(s) for SBWMV resistance, two independent recombinant inbred line populations, Pioneer 26R61/AGS 2000 (PR61/A2000, 178 lines) and AGS 2020/LA 95135 (A2020/LA, 130 lines), were developed. Pioneer 26R61 and AGS 2020 were resistant to SBWMV, and AGS 2000 and LA 95135 were susceptible. Based on the whole genome genotyping for the PR61/A2000 population and targeted mapping of chromosome 5D for the A2020/LA, the same major QTL QSbm.uga-5DL was identified in all environments with highly significant LOD values, explaining up to 62 and 65?% of the total phenotypic variation in the PR61/A2000 and A2020/LA populations, respectively. The location of the resistance QTL coincided with previously published SBCMV resistance genes Sbm1, Sbm _Claire and Sbm _Tremie on the long arm of chromosome 5D. A conserved locus was therefore proposed for conditioning SBWMV/SBCMV resistance in common wheat. Validation of the QTL using the flanking markers Xbarc177 and Xbarc161 in three cultivars and three elite lines with Pioneer 26R61 in their pedigrees indicated that the markers were suitable for marker-assisted selection.     

Mapping and diagnostic marker development for Soil-borne cereal mosaic virus resistance in bread wheat

Monogenically-inherited resistance to Soil-borne cereal mosaic virus (SBCMV) in hexaploid bread wheat cultivars ‘Tremie’ and ‘Claire’ was mapped on chromosome 5D. The two closest flanking markers identified in the Claire-derived mapping population, Xgwm469-5D and E37M49, are linked to the resistance locus at distances of 1 and 9 cm, respectively. Xgwm469-5D co-segregated with the SBCMV resistance in the Tremie-derived population and with the recently identified Sbm1 locus in the cv. Cadenza. This suggested that Tremie and Claire carry a resistance gene allelic to Sbm1, or one closely linked to it. The diagnostic value of Xgwm469-5D was assessed using a collection of SBCMV resistant and susceptible cultivars. Importantly, all susceptible genotypes carried a null allele of Xgwm469-5D, whereas resistant genotypes presumably related to either Claire and Tremie or Cadenza revealed a 152 or 154 bp allele of Xgwm469-5D, respectively. Therefore, Xgwm469-5D is well suited for marker assisted selection for SBCMV resistance.     

Root responses to cereal cyst nematode (Heterodera avenae) in hosts with different resistance genes

The development of cereal cyst nematode (CCN; Heterodera avenae ) induced syncytia in the host roots of infected resistant bread wheat ( Triticum aestivum cv. AUS10894), diploid wheat ( Aegilops tauschii ), barley ( Hordeum vulgare cv. Chebec and cv. Galleon) and in the susceptible wheat cv. Meering and barley cv. Clipper were studied over a period of 13 d. The resistance to CCN in these cereal plants is conferred by the resistance genes Cre1 in the wheat cv. AUS10894, Cre3 in A. tauschii , Ha2 in barley cv. Chebec and Ha4 in barley cv. Galleon. Anatomical observations were made on the development of the syncytia in CCN-infected wheat and barley roots, which carry each of these four sources of resistance genes. Accelerated development of the syncytia in resistant plants, especially in the barley cultivars, was observed. The sites of syncytia development in susceptible wheat and barley were also closely associated with the vascular tissues in the stele, but less so in the resistant plants. The syncytia in the infected susceptible wheat and barley were also metabolically active at day 13. By contrast, the syncytia of resistant wheat plants carrying the Cre1 or Cre3 genes remained extensively vacuolated and less metabolically active. In barley plants with the Ha2 or Ha4 genes, the syncytia appeared non-functional and in early stages of degeneration by day 13 after inoculation.     

Evidence of HIV exposure and transient seroreactivity in archived HIV-negative severe hemophiliac sera

Amino acid sequence analyses indicate that the Soilborne wheat mosaic virus (SBWMV) 19K protein is a cysteine-rich protein (CRP) and shares sequence homology with CRPs derived from furo-, hordei-, peclu- and tobraviruses. Since the hordei- and pecluvirus CRPs were shown to be pathogenesis factors and/or suppressors of RNA silencing, experiments were conducted to determine if the SBWMV 19K CRP has similar activities. The SBWMV 19K CRP was introduced into the Potato virus X (PVX) viral vector and inoculated to tobacco plants. The SBWMV 19K CRP aggravated PVX-induced symptoms and restored green fluorescent protein (GFP) expression to GFP silenced tissues. These observations indicate that the SBWMV 19K CRP is a pathogenicity determinant and a suppressor of RNA silencing.     

The Sbm1 locus conferring resistance to Soil-borne cereal mosaic virus maps to a gene-rich region on 5DL in wheat.

A mosaic disease caused by Soil-borne cereal mosaic virus (SBCMV) is becoming increasingly important, particularly in winter wheat in Europe. As there are currently no effective cultural practices or practical environmentally friendly chemicals for disease control, host plant resistance is an important objective in breeding programs. However, development of resistant cultivars is slow owing to difficulties in germplasm screening for resistance. Therefore, there is a need to identify molecular markers linked to SBCMV-resistance gene(s), so that quick and accurate laboratory-based marker-assisted selection rather than prolonged field-based screens for resistance can be used in developing resistant cultivars. We previously demonstrated that resistance to SBCMV in Triticum aestivum 'Cadenza' is controlled by a single locus. In this work, we used AFLP and microsatellite technology to map this resistance locus, with the proposed name Sbm1, to the distal end of chromosome 5DL. Interestingly, several expressed disease-resistance gene analogues also map to this gene-rich region on 5DL. Closely linked (approximately 17 cM interval) markers, BARC110 and WMC765, RRES01 and BARC144, that flank Sbm1 will be very useful in breeding for selection of germplasm carrying Sbm1.     

禾谷多粘菌对小麦梭条斑花叶病毒的传播及其土壤侵染潜力的测定

从大田侵染小麦梭条斑花叶病毒的小麦病根中挑取禾谷多粘菌休眠孢子堆,接种受侵染小麦品种扬麦４号,经砂培养纯化,获得５个禾谷多粘菌分离物,但都为无毒。无毒多粘菌休眠孢子堆接种表现ＷＳＳＭＶ症状的小麦,经培养可饲获病毒,并可经接咱后将病毒传播给无病小麦,供试的４个大小麦禾谷多粘菌分离物都可对大小进行交叉侵染,产生同样数量的游动孢子产量。供试５个病土和２个无病土样品,都具有强大持多粘菌侵染潜力,即使稀释放     

High Levels of Resistance in Agropyron Species to Barley Yellow Dwarf and Wheat Streak Mosaic Viruses

Several Agropyron species were tested for new sources of resistance to barley yellow dwarf virus (Bydv ) and wheat streak mosaic virus (WSMV). With BYDV strain PAV, 11 of the 17 Agropyron species showed no virus transmission when plants were given access feed by viruliferous Rhopalosiphum padi. Similar trials with BYDV strain RMV (vectored by R. maidis) indicated that all plants, except susceptible control plants, remained virus free. Virus status was confirmed by enzyme-linked immunosorbent assays. When plants were mechanically inoculated with WSMV, 11 Agropyron species failed to express symptoms, while five other species showed a segregating response or had some accessions segregating and some resistant. Test results suggest that resistance to BYDV and WSMV in Agropyron species does not appear to be correlated with any specific genome of Agropyron species although most of the Agropyron species containing S genome were resistant to BYDV and WSMV.     

A major QTL for resistance to soil-borne cereal mosaic virus derived from an old Italian durum wheat cultivar

Abstract

The genetic basis of resistance to soil-borne cereal mosaic virus (SBCMV) in the Triticum turgidum L. var. durum cv. Neodur was analyzed in this study, using a linkage mapping approach. We performed phenotypic and molecular analyses of 146 recombinant inbred lines derived from the cross Cirillo (highly susceptible)×Neodur (highly resistant). A major quantitative trait locus (QTL) that explained up to 87% of the observed variability for symptom severity was identified on the short arm of chromosome 2B, within the 40-cM interval between the markers Xwmc764 and Xgwm1128, with wPt-2106 as the peak marker. Three minor QTLs were found on chromosomes 3B and 7B. Two markers coding for resistance proteins co-segregate with the major QTL on chromosome 2B and the minor QTL on chromosome 3B, representing potential candidate genes for the two resistance loci. Microsatellite markers flanking the major QTL were evaluated on a set of 25 durum wheat genotypes that were previously characterized for SBCMV resistance. The allelic composition of the genotypes at these loci, together with pedigree data, suggests that the old Italian cultivar Cappelli provided the SBCMV-resistance determinants to durum cultivars that have been independently bred in different countries over the last century.     

Screening for Barley yellow dwarf virus-Resistant Barley Genotypes by Assessment of Virus Content in Inoculated Seedlings

The content of Barley yellow dwarf virus (BYDV) in roots and leaves of barley seedling plants differing in their level of resistance was assessed by quantitative ELISA 1–42 days after inoculation with the strain of BYDV (PAV). High virus accumulation in roots and low concentration in leaves was characteristic of the period 9–15 days after inoculation. In leaves, the differences in virus content between resistant and susceptible genotypes became significant after 15 days and resistance to virus accumulation was better expressed 30–39 days after inoculation. Roots of resistant materials exhibited evident retardation of virus accumulation and the greatest difference in virus content between resistant and susceptible plants was detected 9 days after inoculation. By these criteria, the selected winter and spring barley cultivars and lines (in total 44 materials) fell in to five groups according to field reactions and the presence or absence of the Yd2 resistance gene. There were highly significant and positive relations between ELISA values and 5‐year field data on symptomatic reactions and grain‐yield reductions due to infection. Using the described method, resistant and moderately resistant genotypes (both Yd2 and non‐Yd2) were significantly differentiated from susceptible genotypes. The possible use of this method in screening for BYDV resistance is discussed.