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Barley (Hordeum vulgare), cheat (Bromus secalinus), corn (Zea mays), oat (Avena sativa), rye (Secale cereale), and wheat (Triticum aestivum) were infected by a Kansas isolate of the High Plains virus (HPV) in greenhouse experiments, but several other grass species were not. Infection of a host was dependent upon wheat curl mite numbers. Although both green foxtail (Setaria viridis) and yellow foxtail (S. glauca) are found naturally infected by HPV, only yellow foxtail could be infected in greenhouse experiments. Field sampling (1994 to 1996) of symptomatic yellow foxtail showed that it is a good indicator of the presence of HPV, with 252 of 278 symptomatic plants testing positive in enzyme-linked immunosorbent assay (ELISA) for HPV, 2 of 278 for American wheat striate mosaic virus, and 1 of 278 for johnson grass mosaic virus, whereas 23 of 278 symptomatic plants were negative for all viruses tested by ELISA and were not infectious in back-assays.

Sorghum (Sorghum bicolor) was infected by a mechanically transmissible, flexuous, rod-shaped virus. Antiserum made against the purified virus reacted specifically in enzyme-linked immunosorbent assay to the virus and to the potexvirus foxtail mosaic virus (FoMV), indicating that the sorghum virus was an isolate of FoMV. Comparison of the sorghum isolate (H93) to FoMV PV 139 showed that H93 differed biologically by causing severe symptoms in sorghum, not readily infecting certain barley lines, and causing only faint symptoms in barley. At the molecular level, the capsid of H93 had a mass of 23.9 kDa and 217 amino acid residues compared with 23.7 kDa and 215 residues previously reported for the nucleic acid sequence of FoMV. The amino acid sequences of the two viruses were greater than 96% identical. They varied by having four substitutions, one deletion, and three insertions between residues 66 and 67. This is the first report of natural infection of sorghum by FoMV, thus extending its host range among cereal crops.

The High Plains virus (HPV), which infects corn and other cereals, was first found in 1993 in the United States. Research was initiated in 1995 to investigate the potential for seed transmission of HPV. Sweet corn seeds of various cultivars harvested in 1994 to 1996 from 13 fields and research plots in southwestern Idaho, Colorado, and Nebraska were seeded in potting mix in the greenhouse. Leaf samples collected at the three- to six-leaf stage from both symptomatic and asymptomatic plants were tested by enzyme-linked immunosorbent assay (ELISA). Of the 46,600 seeds planted, 38,473 seedlings emerged, and three tested positive by ELISA, exhibited mosaic symptoms, and had the presence of HPV confirmed by an additional test. One of the positive plants was used for successful acquisition and transmission of HPV by the wheat curl mite to Westford barley. The other two plants were used to successfully transfer HPV to other corn plants by vascular puncture inoculation of seed. These results indicate that HPV can be seed transmitted at a very low frequency in sweet corn.

High Plains virus (HPV) isolates from Colorado, Idaho, Kansas, Texas, and Utah were serologically related, had similar relative molecular masses (sodium dodecyl sulfate-polyacrylamide gel electrophoresis) for the 32-kDa diagnostic HPV protein, and were transmissible and maintained free of Wheat streak mosaic virus (WSMV) by vascular puncture inoculation. Collections of wheat curl mites (Aceria tosichella Keifer; WCM) from Kansas, Montana, Nebraska, South Dakota, and Texas differentially transmitted these isolates. For collections from South Dakota and Texas, little or no HPV transmission occurred, whereas WCM from Nebraska and Montana transmitted all five isolates. The collection from Kansas mostly transmitted only one HPV isolate. Aviruliferous or viruliferous WSMV Nebraska WCM transmitted HPV at similar rates and aviruliferous Montana WCM transmitted HPV at lower levels than viruliferous Montana WCM.

Wheat with yellow head disease (YHD) (yellow heads and mosaic leaf symptoms) has been observed in Kansas since 1997. A pathogen was transmitted from the infected wheat to maize by vascular puncture inoculation and to Nicotiana benthamiana by rub inoculation. The original infected wheat and infected maize and N. benthamiana test plants all produced a unique 32- to 34-kDa protein when analyzed by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). Time-of-flight mass spectrometry analysis of the unique 32- to 34-kDa protein showed that the amino acid sequence was most closely related to the nucleoprotein of Rice hoja blanca virus, indicating that the virus causing YHD symptoms in wheat is a tenuivirus. Antiserum made to this protein failed to react with extracts made from healthy wheat or wheat infected with Wheat streak mosaic virus or the High Plains virus. The antiserum did react to extracts made from symptomatic wheat, maize, and N. benthamiana, shown by SDS-PAGE to contain the unique protein, and to extracts of wheat with YHD symptoms from Kansas, North Dakota, South Dakota, and Oklahoma. The name Wheat yellow head virus is proposed for this virus.

Wheat streak mosaic virus (WSMV) infection reduces seed yield and quality in wheat. These losses can be alleviated significantly by exploiting genetic host plant resistance. A new source of temperature-sensitive resistance to WSMV, KS03HW12, and its parental lines (KS97HW29/ KS97HW131//KS96HW100-5) were evaluated in both greenhouse and field conditions. Parental wheat lines were exposed to WSMV pressure under different temperatures in growth chambers to determine the stability of the resistance, and 2 years of field yield trials were conducted to confirm effectiveness. To determine the effectiveness of its resistance against a spectrum of isolates, KS03HW12 was tested against six different WSMV isolates of different geographic origins. Among the three pedigree parents, only one, KS97HW29, was resistant. The parental lines of KS97HW29 are not available for testing; therefore, the presumed origin of the resistance could not be further confirmed. None of the six tested WSMV isolates systemically infected KS03HW12 at 18°C. Yield of KS03HW12 in field tests was not different from healthy controls. Thus, the elite winter wheat KS03HW12 appears to be a stable and effective source of temperature-sensitive resistance to WSMV and should be useful for wheat breeding programs.

Triticum mosaic virus (TriMV) infects wheat (Triticum aestivum) in the Great Plains region of the United States. This study determined the occurrence of TriMV at three locations over 3 years and yield effects of wheat mechanically infected with TriMV. Wheat infection with TriMV, Wheat streak mosaic virus (WSMV), and the High Plains virus (HPV) was verified using enzyme-linked immunosorbent assay. Both wheat singly infected with TriMV and doubly infected with TriMV and WSMV occurred at three, two, and one locations in 2007, 2008, and 2009, respectively. Wheat singly infected with HPV occurred at one and two locations in 2008 and 2009, respectively. Wheat doubly infected with WSMV and HPV occurred at one location in 2008 and 2009. Infection with TriMV declined at two locations each year and, at the third location, it increased the second year and was not detected the third year. WSMV infection increased, except for a decline the third year at one location. In contrast to 3.0% infection of wheat with TriMV and WSMV at one location, 85% of the wheat 1.6 km from that site was infected with TriMV and WSMV in 2009. Infection of wheat with TriMV caused significant yield and volume weight reductions in Danby, RonL, and Jagalene but not KS96HW10-3 wheat.

Temperature-sensitive resistance (TSR) that can protect against losses to Wheat streak mosaic virus (WSMV) has been described in elite wheat germplasm. A TSR identified in the advanced breeding line CO960333 and its derivative KS06HW79 was examined in growth-chamber tests conducted under constant temperature regimes of 18, 21, and 24°C against an array of WSMV isolates. At 18°C, all tested isolates systemically infected the pedigree parents, while the progeny line CO960333 remained free of symptoms; at 24°C, all lines were susceptible. At the intermediate temperature of 21°C, the TSR of KS06HW79 was effective in contrast to the TSRs of KS03HW12 and ‘RonL’. In field trials conducted in 2011 and 2012, the TSR expressed in KS06HW79 conferred complete protection against yield losses from inoculation with the Sidney 81 isolate of WSMV, while the TSR of RonL conferred similar protection in 2012 but allowed small losses in 2011. The resistance expressed by KS06HW79 is likely not due to the Wsm1 gene because it did not contain the tightly linked J15 sequence-characterized amplified region (SCAR) DNA marker. These findings suggest that KS06HW79 could be an additional TSR source of value to wheat-breeding programs seeking to control losses from WSMV.

Triticum mosaic virus (TriMV) is a recently discovered virus infecting wheat. A total of 170 isolates of TriMV, collected in 2010 and 2011 from wheat (Triticum aestivum L) or jointed goatgrass (Aegilops cylindrica Host) from Colorado, Kansas, Nebraska and South Dakota, were compared with the 06-123 Kansas isolate. These isolates were compared for the percentage of infected plants in N28Ht maize, ‘Gallatin’ barley and ‘Mace’ wheat (with temperature-sensitive resistance to Wheat streak mosaic virus (WSMV). The isolates were also compared for the effect of inoculum virus titre on the percentage of infected plants in WSMV-susceptible ‘Tomahawk’ wheat by mechanically inoculating the cultivar using 1:10 w/v, 1:300 v/v or 1:600 v/v dilutions of extracts. None of the isolates infected N28Ht maize but all isolates infected ‘Gallatin’ barley, ‘Mace’ and ‘Tomahawk’ wheat. Some isolates from Colorado, Kansas and Nebraska had low relative titre in wheat compared with the 06-123 isolate. This information is imp...

Expressing temperature-sensitive resistance (TSR) protects wheat against yield losses from infection with Wheat streak mosaic virus (WSMV). In examining how 2,429 wheat accessions from the National Small Grains Collection responded to inoculation with the Sid81 isolate of WSMV, 20 candidate TSR sources were discovered. To differentiate their relative effectiveness, accession responses over 21 days to inoculation with GH95, Sid81, and PV57 virus isolates in regimes of 18 and 20°C were observed. At 18°C, all 20 candidate TSR sources were uniformly or nearly uniformly asymptomatic 21 days after inoculation with the PV57 isolate, resistance indistinguishable from resistant checks KS96HW10-3 and RonL. By contrast, the Sid81 isolate induced symptoms in low but significant proportions of plants of two candidates, and the GH95 isolate in high proportions for four candidates and low but significant proportions for two others. In the more stringent 20°C regime, the uniform or near-uniform induction of symptoms in response to inoculation with GH95 failed to differentiate among the 20 candidate TSR sources and two resistant checks, while PV57 and Sid81 identified several candidates that performed similarly to KS96HW10-3 and significantly better than RonL. By identifying new sources of resistance, this study contributes to the control of WSMV.

Triticum mosaic virus (TriMV) is a recently discovered virus infecting wheat. We compared Colorado isolates C10-492 and C11-775 with the 06-123 isolate. Comparisons were made using enzyme-linked immunosorbent assay (ELISA), infectivity assay, host range, dry weight (DW), inoculation of ‘Mace’ wheat with temperature-sensitive resistance to Wheat streak mosaic virus, and the deduced amino acid sequence of the coat proteins (CP) and P1 proteins. Both C10-492 and C11-775 infected ‘Gallatin’ barley and, when compared with 06-123, had significantly reduced ELISA values and virus titers in wheat. Both Colorado isolates caused symptomless infections in Mace, whereas 06-123 caused mosaic symptoms. The amino acid sequences of the CP differed by two and one amino acids for C10-492 and C11-775, respectively, compared with 06-123. The sequence of C10-492 differed from C11-775 by one amino acid. The P1 amino acid sequence of C10-492 and C11-775 differed from 06-123 by three and one amino acids, respectively. The C10-492 and C11-775 isolates reduced DW significantly in ‘Karl 92’ but significantly less than 06-123. In ‘2317’ wheat, the Colorado isolates did not consistently cause significant reduction in DW, while 06-123 did. The data collectively indicate that C10-492 and C11-775 are isolates of TriMV showing biological behavior diverse from that of 06-123.

Wheat curl mite (WCM)-transmitted viruses—namely, Wheat streak mosaic virus (WSMV), Triticum mosaic virus (TriMV), and the High Plains virus (HPV)—are three of the wheat-infecting viruses in the central Great Plains of the United States. TriMV is newly discovered and its prevalence and incidence are largely unknown. Field surveys were carried out in Colorado, Kansas, Nebraska, and South Dakota in spring and fall 2010 and 2011 to determine TriMV prevalence and incidence and the frequency of TriMV co-infection with WSMV or HPV in winter wheat. WSMV was the most prevalent and was detected in 83% of 185 season–counties (= s-counties), 73% of 420 season–fields (= s-fields), and 35% of 12,973 samples. TriMV was detected in 32, 6, and 6% of s-counties, s-fields, and samples, respectively. HPV was detected in 34, 15, and 4% of s-counties, s-fields, and samples, respectively. TriMV was detected in all four states. In all, 91% of TriMV-positive samples were co-infected with WSMV, whereas WSMV and HPV were mainly detected as single infections. The results from this study indicate that TriMV occurs in winter wheat predominantly as a double infection with WSMV, which will complicate breeding for resistance to WCM-transmitted viruses.

In 2006, a previously unknown wheat (Triticum aestivum) virus was discovered in Western Kansas and given the name Triticum mosaic virus (TriMV). TriMV has since been found in wheat samples isolated all across the Great Plains. Even though it can infect singularly, TriMV is mostly found with Wheat streak mosaic virus (WSMV) as a co-infection. The potential for TriMV to cause economic loss is significant, but very little is known about the virus. The objective of this study was to survey the TriMV population for genetic variation by nucleotide sequencing of isolates across a geographical region. A secondary objective was to characterize the WSMV isolates that are being co-transmitted with TriMV. Fourteen different TriMV isolations were taken from locations in Texas, Oklahoma, and Kansas, and the coat protein cDNA was sequenced. Thirteen nucleotide differences were found in the TriMV isolates, of which three induce amino acid changes. WSMV isolates had 65 nucleotide changes when compared to WSMV Sydney81. Our results indicate the TriMV virus population has minimal amounts of sequence variation and no singular WSMV genotype is specifically associated with TriMV co-infection. Based on the isolates analyzed, it appears that the field population of TriMV is very homogeneous.

‘Snowmass’ (Reg. No. CV-1050, PI 658597) hard white winter wheat (Triticum aestivum L.) was developed by the Colorado Agricultural Experiment Station and released in July 2009 through a marketing agreement with the Colorado Wheat Research Foundation. In addition to researchers at Colorado State University (CSU) and Kansas State University (KSU), USDA-ARS researchers at Manhattan, KS, St. Paul, MN, and Pullman, WA, participated in its development. Snowmass was selected from the cross KS96HW94//‘Trego’/CO960293 made in 1999 at Fort Collins, CO, with the initial F 1 between Trego and CO960293 made by KSU at Hays, KS. KS96HW94 is an unreleased experimental line from KSU with the pedigree ‘Arlin’ (PI 564246)/KS89H20. Trego is a hard white winter wheat cultivar released by KSU in 1999. CO960293 is an unreleased experimental line from CSU from which the germplasm release CO960293–2 was selected. Snowmass was selected as an F 6:7 line in July 2006 and assigned experimental line number CO03W054–2. Snowmass was released because of its superior grain yield under nonirrigated production conditions in eastern Colorado; its resistance to Wheat streak mosaic virus, stripe rust (Puccinia striiformis f. sp. tritici), and stem rust (P. graminis f. sp. tritici); and its superior milling and bread-baking quality.

Triticum mosaic virus (TriMV) is a newly discovered virus isolated from wheat (Triticum aestivum). This study was conducted to determine an experimental host range for TriMV and identify species that could serve as differential hosts for isolating TriMV from Wheat streak mosaic virus (WSMV). Plants tested were mechanically inoculated with the 06-123 isolate of TriMV or the Sidney 81 isolate of WSMV. Some plants were analyzed by enzyme-linked immunosorbent assay (ELISA) using antibodies of TriMV and WSMV. Plants infected with TriMV always produced mosaic symptoms and only extracts of symptomatic plants reacted with antibodies of TriMV. Maize is not a host for TriMV but barley, oat, rye, and triticale are hosts of TriMV. Certain barley and triticale accessions are hosts for TriMV but not WSMV. These plants can be used in combination with maize to separate WSMV and TriMV in plants infected by both viruses. We also showed that 8 wild grass species were susceptible to TriMV and 25 were not. All of the grasses susceptible to infection with TriMV have been reported as susceptible to infection with WSMV. Because of their growth habits, these plant species would be less desirable for use as differential hosts than maize, barley, and triticale.

The properties of two virus isolates (U04-82 and U04-83) obtained from two wheat (Triticum aestivum) plants expressing mosaic symptoms were investigated using enzyme-linked immunosorbent assay (ELISA), sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), time-of-flight mass spectrometry (TOFMS), and infection of wheat with resistance to Wheat streak mosaic virus (WSMV). The coat protein mass was estimated by SDS-PAGE as approximately 32 kDa for U04-82 and 30 kDa for U04-83. The amino acid sequence of the coat protein of U04-82 was 99.6 and 85.5% identical to two isolates, ABC58222 and TX96, respectively, of High Plains virus (HPV) described from Texas. U04-82 was transmitted by wheat curl mites and caused significant yield reductions in wheat resistant to WSMV. U04-83 was actually two distinct virus isolates whose capsid protein amino acid sequences were only 57 and 50% similar to that of TX96. Antiserum prepared to a synthetic peptide from the sequence of the U04-83 isolate recognized the two U04-83 isolates, but not the U04-82 isolate.

To date, only one gene conferring resistance to Wheat streak mosaic virus (WSMV) designated as Wsm1 was transferred from Thinopyrum intermedium (Host) Barkworth and Dewey to wheat (Triticum aestivum L.) in the form of a compensating Robertsonian translocation T4DL·4J s S. Wsm1 confers high levels of resistance to WSMV under fi eld conditions; however, in certain genetic backgrounds and environments, the presence of the T4DL·4J s S translocation reduces agronomic performance. The objective of this study was to shorten the Th. intermedium segment in the T4DL·4J s S translocation. We recovered one proximal (rec36) and four distal (rec45, rec64, rec87, rec213) primary recombinants. Genomic in situ hybridization and molecular marker analyses determined the size of the Th. intermedium segments in the distal recombinants to be about 20% of the 4DS-4J s S arm. All primary recombinant stocks, together with appropriate controls, were evaluated for their resistance to WSMV and Triticum mosaic virus (TriMV) in greenhouse tests. Whereas the distal recombinants rec45, rec64, rec87, and rec213 were resistant to both WSMV and TriMV at low temperatures of 18°C, the proximal recombinant rec36 reacted susceptible, which mapped the Wsm1 gene to the distal 20% of the 4DS-4J s S arm. We successfully shortened the Th. intermedium segment while still retaining the Wsm1 gene. The T4DL·4DS4J s S recombinant chromosome of the rec213 stock was transferred to adapted Kansas hard red winter wheat cultivars.

Triticum mosaic virus (TriMV) is a newly discovered virus found infecting wheat (Triticum aestivum) in Kansas. This study was conducted to determine if the wheat curl mite (WCM, Aceria tosichella) and the bird cherry oat aphid (Rhopalosiphum padi) could transmit TriMV. Using different sources of WCM and two different isolates of TriMV, we were able to show the WCM is the vector of TriMV. Field analysis by enzyme-linked immunosorbent assay (ELISA) demonstrated natural infection patterns of wheat infected with TriMV, Wheat streak mosaic virus (WSMV), or both TriMV and WSMV, putatively infected by viruliferous WCM from a volunteer source growing adjacent to the wheat. Moreover, by single WCM transfers using WCM obtained from different wheat plants naturally infected with TriMV and WSMV and naturally infested with WCM, we showed that these WCM also transmitted TriMV only to wheat or transmitted both TriMV and WSMV to wheat. The infection rates of wheat with TriMV only using WCM transmission was low in both laboratory and field analyses. However, field analyses by ELISA showed that levels of infection of wheat by both TriMV and WSMV were high. No transmission of TriMV to wheat by R. padi occurred in our studies.

In 2006, a mechanically-transmissible and previously uncharacterized virus was isolated in Kansas from wheat plants with mosaic symptoms. The physiochemical properties of the virus were examined by purification on cesium chloride density gradients, electron microscopy, sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), sequencing of the nucleotides and amino acids of the coat protein, and immunological reactivity. Purified preparations contained flexuous, rod-shaped particles that resembled potyviruses. The coat protein was estimated from SDS-PAGE to have a mass of approximately 35 kDa. Its amino acid sequence, as deduced from DNA sequencing of cloned, reverse-transcribed viral RNA and separately determined by time-of-flight mass spectrometry, was most closely related (49% similarity) to Sugarcane streak mosaic virus, a member of the Tritimovirus genus of the family Potyviridae. The virus gave strong positive reactions during enzyme-linked immunosorbent assays using polyclonal antibodies raised against purified preparations of the cognate virus but gave consistent negative reactions against antibodies to Wheat streak mosaic virus (WSMV), other wheat potyviruses, and the High Plains virus. When the virus was inoculated on the WSMV-resistant wheat cv. RonL, systemic symptoms appeared and plant growth was diminished significantly in contrast with WSMV-inoculated RonL. Taken together, the data support consideration of this virus as a new potyvirus, and the name Triticum mosaic virus (TriMV) is proposed.

The “32-kDa” protein specifically associated with high plains disease was characterized by time-of-flight mass spectrometry, after the agent had been isolated in pure culture by “vascular puncture inoculation,” a novel mechanical means of transmission. Two isolates from different geographic locations each consisted of a mixture of subpopulations that were highly homologous to an amino acid sequence derived from a nucleotide sequence (U60141) deposited in GenBank™ by the Nebraska group as “the probable N-protein of high plains virus.” However, the U60141 sequence was found to be incomplete; de novo sequencing of peptides produced by proteolytic digestions of the 32-kDa band from an SDS-PAGE separation showed that an additional 18 amino acid residues were present at the N terminus. BLAST (basic local alignment search tool) examination of the sequence showed no significant homology with any protein in the databases, indicating that the infectious agent of high plains disease is likely a member of a hitherto unclassified virus group.

Nucleotide (nt) sequence polymorphism within a collection of Wheat streak mosaic virus (WSMV) isolates was examined. An approximately 1267-nt region encompassing the coat protein (CP) cistron and flanking sequences was amplified by reverse transcription-polymerase chain reaction (RT-PCR) for each of 49 isolates not previously sequenced. Consensus sequences were compiled for each isolate based on sequences derived from three clones per RT-PCR product. Among 59 consensus sequences examined, only two were identical. Clades A-C contained divergent isolates from Mexico (Clade A); the Czech Republic, Hungary, and Russia (Clade B); and Iran (Clade C). Fifty-four closely related consensus sequences of isolates from the U.S. (51 sequences), Canada (1 sequence), and Turkey (2 sequences) comprised Clade D. Pair-wise nt divergence between two of the most distantly related sequences (Sidney 81 of Clade D and El Batán 3 of Clade A) was 20%, representing over half of the variable sites (34.1%) in the entire WSMV data set. Maximum pairwise nt divergence within Clade D was 3.6%, yet the proportion of all variable sites within Clade D (21.4%) was similar to that of the Sidney 81-El Batán 3 pair. Patterns of polymorphism within Clade D and the Sidney 81-El Batán 3 pair were remarkably similar with respect to synonymous, nonsynonymous, and noncoding substitutions, as were the proportions of substitutions as a function of nt position within codons. The majority of substitutions within Clade D were synonymous and randomly distributed throughout the coding region examined, whereas nonsynonymous substitutions exhibited a clumped distribution and mostly occurred within the 5'-proximal portion of the CP cistron. Because over half of the polymorphic sites within Clade D were of allele size class 1, the isolates appear to be evolving independently and in a nondeterministic manner, within the constraints of selection. These results indicate that Clade D has undergone substantial and, most likely, recent divergence with the majority of consensus sequence substitutions potentially neutral with respect to fitness. An estimate of evolution rate suggests that the present diversity within the U.S. population arose in about a century, a timeframe corresponding to the establishment of wheat monoculture in the Great Plains.

North American and Eurasian isolates of Wheat streak mosaic virus (WSMV; genus Tritimovirus) and Oat necrotic mottle virus (ONMV; genus Rymovirus) were examined. Nine WSMV isolates differentially infected oat, barley, inbred maize line SDp2 and sorghum line KS56. The WSMV isolates clustered into groups based on phylogenetic analyses of the capsid protein (CP) cistron and flanking regions. WSMV isolates from the United States (US) and Turkey were closely related, suggesting recent movement between continents. Although more divergent, WSMV from Iran (WSMV-I) also shared a most recent common ancestor with the US and Turkish isolates. Another group of WSMV isolates from central Europe and Russia may represent a distinct Eurasian population. Complete genome sequences of WSMV from the Czech Republic (WSMV-CZ) and Turkey (WSMV-TK1) were determined and comparisons based on complete sequences yielded relationships similar to those based on partial sequences. ONMV-Pp recovered from blue grass (Poa pratensis L.) in Germany displayed the same narrow host range as ONMV-Type from Canada. Western blots revealed a heterologous relationship among CP of WSMV and ONMV. Phylogenetic analyses of the capsid protein cistron and flanking genomic regions indicated that WSMV and ONMV are related species sharing 74·2–76·2% (nucleotide) and 79·2–81·0% (amino acid) identity. Thus, ONMV should be removed from the genus Rymovirus and designated a definitive member of the genus Tritimovirus. Phylogenetic analyses further suggest that Sugarcane streak mosaic virus is not a tritimovirus, and may represent a new genus within the family Potyviridae.

Time-of-flight mass spectrometry (TOFMS) has been applied to determine the complete coat protein amino acid sequences of a number of distinct brome mosaic virus (BMV) isolates. Ionization was carried out by both electrospray ionization and matrix-assisted laser desorption/ionization (MALDI). After determining overall coat protein masses, the proteins were digested with trypsin or Lys-C proteinases, and the digestion products were analyzed in a MALDI QqTOF mass spectrometer. The N terminus of the coat protein was found to be acetylated in each BMV isolate analyzed. In one isolate (BMV-Valverde), the amino acid sequence was identical to that predicted from the cDNA sequence of the "type" isolate, but deviations from the predicted amino acid sequence were observed for all the other isolates analyzed. When isolates were propagated in different host taxa, modified coat protein sequences were observed in some cases, along with the original sequence. Sequencing by TOFMS may therefore provide a basis for monitoring the effects of host passaging on a virus at the molecular level. Such TOFMS-based analyses assess the complete profiles of coat protein sequences actually present in infected tissues. They are therefore not subject to the selection biases inherent in deducing such sequences from reverse-transcribed viral RNA and cloning the resulting cDNA.

Viruses are intercellular parasites with a limited genome, and therefore dependent on the host cell for multiplication and proliferation. When viruses infect plants the usual response is formation of a mosaic symptom, considered to reflect perturbations in the chloroplasts. However, in some instances, plants remain symptomless. In either case, no cellular disruption is documented. This is in contrast to animal viruses, which shut off cellular protein synthesis, culminating in cellular disruption. Yet, generally, infection of plants by viruses results in reduction of plant size and yield. Since most plant virus infection is not accompanied by clear pathogenic damage, there sulting yield reduction caused by it remains an enigma. Most investigations of plant viruses are oriented towards preventing infection, with little attention to host pathogenic damage. However, a better understanding of plant and virus interactions may help explain the mode by which virus infection causes yield reduction. The scientific ...

Wheat with virus-like symptoms (extracts containing a 33-kDa protein in sodium dodecyl sulfate-polyacrylamide gel electrophoresis, negative in enzyme-linked immunosorbent assay to wheat streak mosaic virus, and not infectious in a backassay to other wheat) reacted positively to antiserum made against a protein purified from symptomatic corn infected with the High Plains virus (HPV), indicating a serological relationship between the corn and wheat pathogens. The wheat curl mite (WCM, Aceria tosichella Keifer) was identified as the vector of the virus and caused persistent infection of barley (Hordeum vulgare L.) and wheat (Triticum aestivum L.) in greenhouse experiments. The HPV was recovered in the field from naturally infected wheat where the number of HPV-infected plants decreased with increasing distance from the WCM source in volunteer wheat.

a b s t r a c t Triticum mosaic virus (TriMV), an economically important virus infecting wheat in the Great Plains region of the USA, is the type species of the Poacevirus genus in the family Potyviridae. Sensitive and high-throughput serology-based detection methods are crucial for the management of TriMV and germplasm screening in wheat breeding programs. In this study, TriMV coat protein (CP) was expressed in Escherichia coli, and polyclonal antibodies were generated against purified soluble native form recom- binant CP (rCP) in rabbits. Specificity and sensitivity of resulting antibodies were tested in Western immuno-blot and enzyme-linked immunosorbent assays (ELISA). In direct antigen coating (DAC)-ELISA, antibodies reacted specifically, beyond 1:20,000 dilution with TriMV in crude sap, but not with healthy extracts, and antiserum at a 1:10,000 dilution detected TriMV in crude sap up to 1:4860 dilution. Notably, rabbit anti-TriMV IgG and anti-TriMV IgG-alkaline phosphatase conjugate reacted positively with native virions in crude sap in a double antibody sandwich-ELISA, suggesting that these antibodies can be used as coating antibodies which is crucial for any 'sandwich' type of assays. Finally, the recombinant antibod- ies reacted positively in ELISA with representative TriMV isolates collected from fields, suggesting that antibodies generated against rCP can be used for sensitive, large-scale, and broad-spectrum detection of TriMV.

Wheat (Triticum aestivum L.) yield is limited by wheat streak mosaic virus which is vectored by the wheat curl mite (WCM) Aceria tosicheilla (Keifer). Host resistance to WCM has reduced losses. This study was conducted to evaluate the effectiveness of resistance in wheat to WCM collected from various locations in the Great Plains. Collections of WCM from Montana, Nebraska, South Dakota, Texas, Alberta, Canada, and eight locations in Kansas were compared for their ability to survive and reproduce in the greenhouse on seven lines of wheat and wheat relatives previously identified as resistant. The lines and their sources of resistance were: AC PGR16635 (Aegilops tauschii Coss., Cmc1), PI525452 (Thinopyrum ponticum (Podp.) Liu and Wang, Cmc2), KS96WGRC40 (Ae. tauschii and Secale cereale L.), TA920 (Triticum timopheevii (Zhuk.) Zhuk spp. armenidcum), PI 475772 (S. cereale), TAM 107' (S. cereale), PI 222655 (T. aestivum). KS96WGRC40 and TA920 were the only entries that were resistant to all WCM collections. Other sources of resistance were effective against WCMs from some but not all locations. PI 222655 was resistant to WCMs from Nebraska and central Kansas but not to mites from most other locations. WCMs that were virulent to TAM 107 generally were also virulent to PIs 222655 and 475772 but avirulent to Cmc2. The WCMs from western Kansas, where TAM 107 is widely grown, were generally more virulent to that cultivar than WCM from central Kansas where the hectarage of TAM 107 is smaller. WCMs collected at different times or locations may vary in their responses to different sources of resistance; therefore, testing mites for their response to resistance genes advanced in breeding programs may be needed before resistant cultivars are deployed in the field.

Seifers, D. L., Salomon, R., Marie-Jeanne, V., Alliot, B., Si gnoret, P., Haber, S., Loboda, A., Ens, W., She, Y.-M., and Standing, K. G. 2000. Characterization of a novel potyvirus isolated from maize in Israel. Phytopathology 90:505-513. A potyvirus (proposed name of Zea mosaic virus [ZeMV]) isolated from maize in Israel was analyzed by serology, sodium dodecyl sulfatepolyacrylamide gel electrophoresis (SDS-PAGE) of capsid proteins, symptomatology, and sequencing. Parts of the nuclear inclusion b, coat protein, and 3′ regions were sequenced; the amino acid sequence of ZeMV capsid was determined by time-of-flight mass spectrometry (TOFMS). The results of these analyses were compared with those of similar analyses of the following potyviruses: Maize dwarf mosaic virus (MDMV), Sugarcane mosaic virus strain MDB (SCMV-MDB), Johnsongrass mosaic virus (JGMV), Sorghum mosaic virus (SrMV), and an isolate of MDMV from Israel. Indirect enzyme-linked immunosorbent assay using ZeMV antiserum detected only ZeMV, and reciprocal tests using MDMV, JGMV, or SrMV antisera failed to detect ZeMV. ZeMV cross-reacted weakly when SCMV-MDB antiserum was used. The mass of ZeMV capsid was determined to be 36,810 Da by SDS-PAGE and 34,216 Da by TOFMS. The ZeMV systemically infected johnsongrass (Sorghum halepense), but did not infect oat ( Avena sativa), pearl millet ( Pennisetum glaucum), barley (Hordeum vulgare), or rye (Secale cereale). Necrosis was caused in 19 sorghum lines by SrMV, in 15 by ZeMV, in 14 by MDMV, and in 5 by JGMV and SCMV-MDB. The nucleic acid and amino acid sequences of ZeMV clearly showed that it is not a strain of JGMV, MDMV, SCMV, or SrMV.

Redinbaugh, M. G., Seifers, D. L., Meulia, T., Abt, J. J., Anderson, R. J., Styer, W. E., Ackerman, J., Salomon, R., Houghton, W., Creamer, R., Gordon, D. T., and Hogenhout, S. A. 2002. Maize fine streak virus, a new leafhopper-transmitted rhabdovirus. Phytopathology 92:1167-1174. A previously uncharacterized virus was isolated from fall-planted sweet corn (Zea mays L., Syngenta GSS 0966) leaves showing fine chlorotic streaks. Symptomatic plants were negative in enzyme-linked immunosorbent assay against many maize viruses, but reacted weakly with antisera to Sorghum stunt mosaic virus suggesting a distant relationship between the viruses. The virus was readily transmitted by vascular puncture inoculation (VPI), but not by leaf-rub inoculation. Symptoms on maize included dwarfing and fine chlorotic streaks along intermediate and small veins that developed 12 to 17 days post-VPI. The isolated virus was bacilliform (231 5 nm long and 71 2 nm wide), with a knobby surface, and obvious helical structure typical of rhabdovirus morphology. Nucleorhabdovirus virions were observed by transmission electron microscopy of infected maize leaf tissue sections. Proteins unique to infected plants were observed in extracts of infected leaves, and the isolated virion contained three proteins with molecular masses 82 2, 50 3, and 32 2 kDa. Preliminary sequence analysis indicated the virus had similarity to members of the family Rhabdoviridae. The virus was transmitted by Graminella nigrifrons under persistent conditions. The data indicate the virus, provisionally designated Maize fine streak virus, is a new species in the genus Nucleorhabdovirus.

A virus isolated from sorghum in Nigeria has been partially characterized. It was tested by enzyme-linked immunosorbent assay (ELISA) using antisera to Maize dwarf mosaic virus, Johnsongrass mosaic virus (JGMV), Sugarcane mosaic virus strain-MDB, Sorghum mosaic virus, and Zea mosaic virus. A partial host range, symptom phenotypes for selected sorghum lines, and the mass of the coat protein (CP) subunit was analyzed by sodium-dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), and its amino acid (aa) sequence determined by time-of-flight mass spectrometry (TOFMS). The Nigerian isolate was positive in ELISA to only JGMV antiserum. It infected sorghum and smooth brome but not oat or johnsongrass. It caused necrosis in 12 of 13 tested sorghum lines, while the USA JGMV isolate caused necrosis in only one sorghum line. In SDS-PAGE, the mass of the Nigerian virus CP was 3,000 Da smaller than that of JGMV-MDO. Moreover, TOFMS analyses showed that, while residues 1-7 of the CP aa sequence were identical to those of JGMV (GenBank #A27631), and residues 57-293 were almost identical to residues 67-303 of JGMV, the intermediate region exhibited significant differences, including a 10 aa deletion. These data indicate that the virus should be considered a distinct isolate of JGMV (JGMV-N) and expands the known range of JGMV to Africa.

The "32-kDa" protein specifically associated with high plains disease was characterized by time-of-flight mass spectrometry, after the agent had been isolated in pure culture by "vascular puncture inoculation," a novel mechanical means of transmission. Two isolates from different geographic locations each consisted of a mixture of subpopulations that were highly homologous to an amino acid sequence derived from a nucleotide sequence (U60141) deposited in GenBank trade mark by the Nebraska group as "the probable N-protein of high plains virus." However, the U60141 sequence was found to be incomplete; de novo sequencing of peptides produced by proteolytic digestions of the 32-kDa band from an SDS-PAGE separation showed that an additional 18 amino acid residues were present at the N terminus. BLAST (basic local alignment search tool) examination of the sequence showed no significant homology with any protein in the databases, indicating that the infectious agent of high plains disease is likely a member of a hitherto unclassified virus group.

(...) Arkan' and TAM 108' had moderate trichome densities on leaves two, four and six (three-leaf mean = 28.4 and 22.8 mm -2 , respectively) and were more heavily infested by WCM in greenhouse and field tests when compared to cultivars (Century, TAM 107, Larned and Newton) that have low trichome densities (6.0, 8.6, 5.0 and 5.7 trichomes mm -2 , respectively). (...)Some cultivars now widely grown in Kansas may have sufficient pubescence to significantly increase their susceptibility to WSMV (...)

Wheat streak mosaic is the most important wheat (Triticum aestivum L.) disease in western Kansas. The wheat cultivar TAM 107 has been resistant to the wheat curl mite (WCM, Aceria tosichella Keifer), which is the vector of wheat streak mosaic virus (WSMV) and as the most popular wheat cultivar in western Kansas has effectively reduced the incidence of the disease. In 1991, several observations indicated that the incidence of WSMV infection in TAM 107 was much heavier than usual. In 1992, a survey of 10 field collections of WCM showed that one collection from TAM 107 was virulent to that cultivar. In 1995, WCM collections from TAM 107 and 'Karl' (susceptible to WCM) were made from 14 western Kansas counties and tested for virulence to TAM 107. All collections of WCM obtained from TAM 107 were adapted to TAM 107, and nine of the 14 collections from Karl were adapted to TAM 107. The high incidence of a WCM strain virulent to TAM 107 may explain the increased losses to WSMV recently observed in that cultivar. TAM 107 probably cannot be relied on in the future to provide protection against WSMV in western Kansas. Lines derived from sources of resistance that are effective against WCM virulent to TAM 107 or that are resistant to WSMV are being advanced in wheat breeding programs and should be deployed in the field as soon as possible.

Agronomically promising wheat (Triticum aestivum) lines are now available that have the short arm of chromosome 4Ai-2 from Agropyron intermedium translocated onto the long arm of wheat chromosome 4D. This translocation confers a high level of resistance to wheat streak mosaic virus (WSMV). In growth chamber tests, we demonstrated that, when the translocation is present, the resistance is effective at 20 but not at 25°C. Lines with the entire Ai-2 chromosome remained symptom-free at both temperatures. In field tests, both naturally infested and mechanically inoculated lines carrying the 4Ai2-S translocation were WSMV symptom free, and grain yields, test weights, and plant height were not reduced by WSMV. The grain yields of WSMV-susceptible cultivars were reduced by 21 to 45% in the same test. Although the WSMV resistance carried on the translocation is high-temperature sensitive, it was effective in the field and continues to be a very promising source for the development of WSMV-resistant cultivars.

Extracts of winter wheat with viruslike symptoms from Comanche County, Kans., did not react with antisera to viruses previously found infecting wheat in the state, nor was the virus mechanically transmissible to wheat, maize, or sorghum. Leaves of infected wheat developed thin, chlorotic striations that were more severe on the abaxial than adaxial surface. The virus reacted with American wheat striate mosaic virus (AWSMV) antiserum and was vectored by the painted leafhopper (Endria inimica), confirming the virus as AWSMV. A protein of 59 kDa, consistently detected in extracts of infected leaves, reacted with antiserum to AWSMV in Western blots. This is the first report of AWSMV in the Southern Great Plains region. Experiments showed that, on some cultivars, AWSMV caused brown necrotic streaking of culms and glumes, a symptom not described previously for wheat infected by this virus. Hard red winter wheat cultivars Ike, Karl, and TAM 107 had positive enzyme-linked immunosorbent assay values, but exhibited few or no symptoms.

Wheat collected in Colorado was found to be infected with both wheat streak mosaic virus (WSMV) and Agropyron mosaic virus (AMV). The viruses were identified by means of host range tests, serology, and electrophoretic comparisons of coat proteins. The AMV isolates (the Colorado isolate and PV 75) were further characterized by partial chemical proteolysis of capsid proteins and electrophoretic analysis of cleavage products and by comparison of single-stranded and double-stranded RNAs. This is the first report of AMV in Colorado (.)

Martin, T. J., Harvey, T. L., Bender, C. G., and Seifers, D. L. 1984. Control of wheat streak mosaic virus with vector resistance in wheat. Phytopathology 74:963-964. Resistance to the wheat curl mite (WCM), Eriophyes tulipae, derived KS80H4200 was reduced by 74% compared to WCM-susceptible cultivar from cultivar Salmon wheat, reduced the incidence of wheat streak mosaic Sage in greenhouse seedling tests. Reduced transmission of WSMV to by 58% in naturally infested wheat nurseries in 1979, 1981, and 1982. The WCM-resistant cultivars coupled with WCM control in WCM-resistant transmission of wheat streak mosaic virus (WSMV) to WCM-resistant volunteer wheat should give effective levels of WSM control. Wheat streak mosaic (WSM) is one of the most destructive line was replicated three times, as was the WCM-susceptible parent diseases of wheat ( Triticum aestivum L.) in the Great Plains region. Sage and the WCM-resistant parent Salmon. One of these Estimates of losses caused by wheat streak mosaic virus (WSMV) segregates, KS78H 1054, was identified previously as homozygous in Kansas include 816>X 106 kg in 1974 (9) and 571 X 106 kg in 1981 resistant to WCM and therefore, it was the only Sage/ Salmon (12). Cultural practices recommended to reduce WSM losses are derivative for which WSM incidence had been determined. The planting late and, destruction of volunteer wheat, the major WCM reaction for the remaining lines was unknown. Total oversummering ho'st for WSMV and its vector, the wheat curl mite number of plants in each row was determined by direct count. The (WCM) (Eriophyes tulipae Keifer) (13). These procedures are not number of WSMV-infected plants in each row was recorded in late always effective. In western Kansas many wheat producers do not May. follow either of these recommendations because volunteer wheat In 1981, WSM again occurred in the breeding nurseries at Hays. often is used for winter grazing and planting date usually is dictated The incidence of WSM was determined on four replications of both by the availability of soil moisture rather than WSM control WCM-resistant and -susceptible lines. The WCM-resistant lines considerations. were derived from the cross Sage/ Salmon/ 3/ Larned/ Eagle/ / Sage. Wheat cultivars with reliable WSMV resistance levels are not There were 10 WCM-resistant lines in the 1981 nursery. Data are available. Low levels of resistance exist in several cultivars under presented for KS80H4200 only, because it was representative of all certain conditions (6), but in many years these cultivars are WCM-resistant lines and was used in the 1982 tests. KS80H4200 damaged severely. High-level WSMV resistance was transferred to was released as germ plasm in 1982 by Kansas State University in wheat from two Agropyron species (5,11). Due to genetic linkage cooperation with USDA-ARS (7). All cultivars used in these tests between WSMV resistance and undesirable agronomic are susceptible to mechanical inoculation with WSMV (6).