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How viruses hitch a ride on pollen to infect plants

How viruses hitch a ride on pollen to infect plants | Cereal and grass viruses | Scoop.it

Pollination is an essential step in the reproduction of flowering plants and is also crucial in agriculture in regard to fruit development, seed output, and the creation of new varieties of plants. However, at least 18 viruses can infect the mother plant through the fertilized flower (horizontal transmission by pollen). Horizontal transmission by pollen is epidemiologically important for viruses infecting perennial crops, since pollen grains from infected trees continue to be scattered every year. The mechanism how pollination with virus-infected pollen grains causes systemic viral infection to healthy plants has been unknown since the first report of horizontal transmission by pollen in 1918.

 


Via Ed Rybicki
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Would be also interesting to analyze mechanisms of the horizontal transmission by pollen of grass infecting viruses like Ryegrass cryptic virus.

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Rescooped by Rabenstein, Frank from Grain du Coteau : News ( corn maize ethanol DDG soybean soymeal wheat livestock beef pigs canadian dollar)
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US wheat rating fails to improve, despite much-needed rain

US winter wheat crops failed to show improvement again despite rains in the drought-hit southern Plains, with dryness worries growing in the north west of the country, and disease incidence taking a higher profile too.

The proportion of US winter rated "good" or "excellent" as of Sunday was 42%, for a third successive week, US Department of Agriculture data showed.

The stable rating defied expectations among many analysts of some improvement in the figure, after reports of rains to refresh crops in the central and southern Plains.

However, the proportion of winter wheat in Kansas, the top wheat growing state, rated "good" or "excellent" remained at a lowly 26%, with rains not proving as widespread as some market talk had indicated.

"Light precipitation was reported in eastern Kansas with amounts up to half an inch, while the west remained dry," USDA scouts said.

In Oklahoma, development of the crop in the state's western panhandle area "continued to suffer due to limited moisture and drought conditions".

And while in Texas crop did improve, by 1 point to 52% rated good or excellent, storms did not prove an unqualified boon to seedlings with scouts reporting "hail damage" in some northern areas, and "some damage due to high winds" further south.

'Decreased water levels'

Meanwhile, crops in some other states deteriorated, including in South Dakota, of which 69% is seen "short" or "very short" of topsoil moisture.

The proportion of South Dakota winter wheat rated good or excellent fell by two points to 23%.

And in the north western US, a major growing area for white wheat, ratings fell in Idaho, Oregon and Washington, the USDA data showed, following a caution last week from US Wheat Associates over the region's harvest prospects.

In central Washington, "the lack of precipitation continued to be of concern, impacts were shown in decreased water levels in reservoirs along with ponds and lakes that are utilised by producers".

In Oregon, scouts noted that in the north of the state in particular "drought impacts were beginning to show and the Deschutes River was running below normal levels".

'Chatter about disease and insects'

There is increasing talk of disease too in US winter wheat, although it is difficult to gauge yet how widespread infections are.

Broker CHS Hedging highlighted "chatter about disease and insects in some hard red winter wheat growing areas, with the possibility that could be the major find on the Wheat Quality Council Hard Winter Wheat Tour set for next week".

In Oklahoma, Bob Hunger, Oklahoma State University Extension plant pathologist flagged a spread of many diseases of in wheat crops, particularly of stripe rust.

"My impression is that stripe rust has activated again with the cool and wet weather, and continues to spread across Oklahoma," he said.

"Mite-transmitted viruses also are prevalent in Oklahoma this year."


Via Stéphane Bisaillon
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Properties of satellite tobacco mosaic virus phenotypes expressed in the presence and absence of helper virus

Highlights•

When co-expressed with helper virus in N. benthamiana but not in N. tabacum, STMV generates a truncated RNA.

A highly conserved 3′ stem-loop structure is obligatory for STMV translation.

STMV is competent to form empty VLPs without helper virus.

STMV assembly requires a 3′ tRNA-like structure.

Abstract

In this study, we assembled an Agrobacterium-based transient expression system for the ectopic expression of Satellite tobacco mosaic virus (STMV) (+) or (−) transcripts and their biological activity was confirmed when Nicotiana benthamiana plants were co-expressed with helper Tobacco mosaic virus replicase. Characterization of STMV in the presence and absence of its HV revealed: (i) HV-dependent expression of STMV (+) in N. benthamiana, but not in N. tabacum, generated a replication-deficient but translation and encapsidation competent variant lacking the highly conserved 3′ 150 nucleotides (nt) (STMVΔ150); (ii) mutational analysis demonstrated that a conserved 3′ stem-loop structure in wild type and STMVΔ150 located between nt 874 and 897 is essential for translation of CP; (iii) helper virus-independent expression of CP from wt STMV was competent for the assembly of empty aberrant virion-like particles; whereas, CP translated from STMVΔ150 resulted in disorganized CP aggregates suggesting a role for the 3′tRNA-like structure in STMV assembly.

KeywordsSatellite viruses; Replication; Packaging; Translation; tRNA-like structure, Brome mosaic virus

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Genetic diversity of viruses associated with sugarcane mosaic disease of sugarcane inter-specific hybrids in China - Online First - Springer

Genetic diversity of viruses associated with sugarcane mosaic disease of sugarcane inter-specific hybrids in China - Online First - Springer | Cereal and grass viruses | Scoop.it
Abstract

In this study, we investigated 78 sugarcane samples with severe mosaic symptoms collected from four provinces of southern China: Guangxi, Yunnan, Hainan, and Guangdong, which cover nearly 85 % of commercial sugarcane planting zones in China. Using RT-PCR, sequencing and phylogenetic analysis, we identified 72 hybrid sugarcane samples containing causal agents of sugarcane mosaic disease. Among these, 66 virus isolates were identified as Sorghum mosaic virus (SrMV) (84.6 %), four were identified as Sugarcane streak mosaic virus (SCSMV) (5.1 %), and two were identified as Sugarcane mosaic virus (SCMV) (2.6 %). The isolates of SrMV were classified into three subgroups: I, II, and III with a 95 % similarity level. The two largest subgroups, SrMV I containing 36 sugarcane mosaic diseases isolates (46.2 %), and SrMV III containing 20 isolates (25.6 %), were prevalent in Guangdong and Guangxi provinces; however, SrMV II containing five isolates (6.4 %) did not exhibit any close association with geographical distribution. The popular sugarcane cultivar, ROC22, was found to be infected with all the three subgroup types of SrMV. According to our knowledge, this is the first reported detection of the co-infection of SrMV and SCSMV in Saccharum hybrid (YN-bs-9). Recombination analysis indicated recombination between different isolates mostly occurring in Yunnan and Guangxi provinces among the SrMV I group. This study provides insight into the species diversity and geographical distribution of causal agents of sugarcane mosaic disease, and provides the basis for its identification, prevention, and future control efforts.

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Rice ragged stunt virus-induced apoptosis affects virus transmission from its insect vector, the brown planthopper to the rice plant : Scientific Reports : Nature Publishing Group

Rice ragged stunt virus-induced apoptosis affects virus transmission from its insect vector, the brown planthopper to the rice plant : Scientific Reports : Nature Publishing Group | Cereal and grass viruses | Scoop.it

Most plant viruses that seriously damage agricultural crops are transmitted by insects. However, the mechanisms enabling virus transmission by insect vectors are poorly understood. The brown planthopper (Nilaparvata lugens) is one of the most serious rice pests, causing extensive damage to rice plants by sucking the phloem sap and transmitting viruses, including Rice ragged stunt virus (RRSV). In this study, we investigated the mechanisms of RRSV transmission from its insect vector to the rice plant in vivo using the terminal deoxynucleotidyl transferase dUTP nick-end labeling assay and RNA interference technology. RRSV induced apoptosis in the salivary gland cells of its insect vector, N. lugens. The RRSV-induced apoptosis was regulated through a caspase-dependent manner, and inhibition of the expression of N. lugens caspase-1 genes significantly interfered with virus transmission. Our findings establish a link between virus-associated apoptosis and virus transmission from the insect vector to the host plant.

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The Lsm1-7-Pat1 complex promotes viral RNA translation and replication by differential mechanisms

Abstract

The Lsm1-7-Pat1 complex binds to the 3′ end of cellular mRNAs and promotes 3′ end protection and 5′–3′ decay. Interestingly, this complex also specifically binds to cis-acting regulatory sequences of viral positive-strand RNA genomes promoting their translation and subsequent recruitment from translation to replication. Yet, how the Lsm1-7-Pat1 complex regulates these two processes remains elusive. Here, we show that Lsm1-7-Pat1 complex acts differentially in these processes. By using a collection of well-characterized lsm1 mutant alleles and a system that allows the replication of Brome mosaic virus (BMV) in yeast we show that the Lsm1-7-Pat1 complex integrity is essential for both, translation and recruitment. However, the intrinsic RNA-binding ability of the complex is only required for translation. Consistent with an RNA-binding-independent function of the Lsm1-7-Pat1 complex on BMV RNA recruitment, we show that the BMV 1a protein, the sole viral protein required for recruitment, interacts with this complex in an RNA-independent manner. Together, these results support a model wherein Lsm1-7-Pat1 complex binds consecutively to BMV RNA regulatory sequences and the 1a protein to promote viral RNA translation and later recruitment out of the host translation machinery to the viral replication complexes.

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Proteomic analysis of interaction between a plant virus and its vector insect reveals new functions of hemipteran cuticular protein

Abstract

Numerous viruses can be transmitted by their corresponding vector insects; however, the molecular mechanisms enabling virus transmission by vector insects have been poorly understood, especially the identity of vector components interacting with the virus. Here, we used the yeast two hybrid system to study proteomic interactions of a plant virus (Rice stripe virus, RSV, genus Tenuivirus) with its vector insect, small brown planthopper (Laodelphax striatellus). Sixty-six proteins of L. striatellus that interacted with the nucleocapsid protein (pc3) of RSV were identified. A virus-insect interaction network, constructed for pc3 and 29 protein homologs of Drosophila melanogaster, suggested that 9 proteins might directly interact with pc3. Of the 66 proteins, five (atlasin, a novel cuticular protein, jagunal, NAC domain protein, and vitellogenin) were most likely to be involved in viral movement, replication and transovarial transmission. This work also provides evidence that the novel cuticular protein, CPR1, from L. striatellus is essential for RSV transmission by its vector insect. CPR1 binds the nucleocapsid protein (pc3) of RSV both in vivo and in vitro and colocalizes with RSV in the hemocytes of L. striatellus. Knockdown of CPR1 transcription using RNA interference resulted in a decrease in the concentration of RSV in the hemolymph, salivary glands and in viral transmission efficiency. These data suggest that CPR1 binds RSV in the insect and stabilizes the viral concentration in the hemolymph, perhaps to protect the virus or to help move the virus to the salivary tissues. Our studies provide direct experimental evidence that viruses can use existing vector proteins to aid their survival in the hemolymph. Identifying these putative vector molecules should lead to a better understanding of the interactions between viruses and vector insects.

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Fine mapping of Msv1, a major QTL for resistance to Maize Streak Virus leads to development of production markers for breeding pipelines - Online First - Springer

Fine mapping of Msv1, a major QTL for resistance to Maize Streak Virus leads to development of production markers for breeding pipelines - Online First - Springer | Cereal and grass viruses | Scoop.it
AbstractKey message

Msv1 , the major QTL for MSV resistance was delimited to an interval of 0.87 cM on chromosome 1 at 87 Mb and production markers with high prediction accuracy were developed.

Abstract

Maize streak virus (MSV) disease is a devastating disease in the Sub-Saharan Africa (SSA), which causes significant yield loss in maize. Resistance to MSV has previously been mapped to a major QTL (Msv1) on chromosome 1 that is germplasm and environment independent and to several minor loci elsewhere in the genome. In this study, Msv1 was fine-mapped through QTL isogenic recombinant strategy using a large F 2 population of CML206 × CML312 to an interval of 0.87 cM on chromosome 1. Genome-wide association study was conducted in the DTMA (Drought Tolerant Maize for Africa)-Association mapping panel with 278 tropical/sub-tropical breeding lines from CIMMYT using the high-density genotyping-by-sequencing (GBS) markers. This study identified 19 SNPs in the region between 82 and 93 Mb on chromosome 1(B73 RefGen_V2) at a P < 1.00E-04, which coincided with the fine-mapped region of Msv1. Haplotype trend regression identified a haplotype block significantly associated with response to MSV. Three SNPs in this haplotype block at 87 Mb on chromosome 1 had an accuracy of 0.94 in predicting the disease reaction in a collection of breeding lines with known responses to MSV infection. In two biparental populations, selection for resistant Msv1 haplotype demonstrated a reduction of 1.03–1.39 units on a rating scale of 1–5, compared to the susceptible haplotype. High-throughput KASP assays have been developed for these three SNPs to enable routine marker screening in the breeding pipeline for MSV resistance.

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SCREENING AND ANTIBIOSIS MECHANISM IN RICE GENOTYPE AGAINST BROWN PLANTHOPPER, NILAPARVATA LUGENS (STAL FOR IDENTIFICATION OF RESISTANCE DONOR

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New Zealand Stresses that It Is High Plains Virus Free, and the Viru Struggles with an Identity Crisis

High Plains virus (HPV), a tentative member of the genus Emaravirus, causes a potentially serious economic disease in cereals.
Recently, in this journal, Tatineni et al. (1) mistakenly reported
HPV as being present in New Zealand, citing the paper by
Lebas et al. from 2005 (2). The 2005 report clearly states that New
Zealand is HPV free in both the abstract and the introduction (2).
To date,HPVis not known to occur in New Zealand. The Ministry
for Primary Industries of New Zealand has very strict regulations
in place to prevent the importation of unwanted organisms
such as HPV. For example, the importation of Zea mays seeds
must follow the requirements stated in Import Health Standard
155.02.05 (for seed for sowing) (3), which includes testing of HPV
by enzyme-linked immunosorbent assay (ELISA) or PCR. The
Tatineni et al. statement (1) will mislead regulatory officials of
New Zealand’s trading partners who regularly monitor world microbe
dynamics in the scientific literature. In fact, there are plant
biosecurity actions in place (4) that directly affect New Zealand’s
international trade when a regulated plant virus like HPV is reported
as present.

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Deep sequencing of dsRNAs recovered from mosaic-diseased pigeonpea reveals the presence of a novel emaravirus: pigeonpea sterility mosaic virus 2 - Online First - Springer

Deep sequencing of dsRNAs recovered from mosaic-diseased pigeonpea reveals the presence of a novel emaravirus: pigeonpea sterility mosaic virus 2 - Online First - Springer | Cereal and grass viruses | Scoop.it

Abstract

Deep-sequencing analysis of double-stranded RNA extracted from a mosaic-diseased pigeonpea plant (Cajanus cajan L., family Fabaceae) revealed the complete sequence of six emaravirus-like negative-sense RNA segments of 7009, 2229, 1335, 1491, 1833 and 1194 nucleotides in size. In the order from RNA1 to RNA6, these genomic RNAs contained ORFs coding for the RNA-dependent RNA polymerase (RdRp, p1 of 266 kDa), the glycoprotein precursor (GP, p2 of 74.5 kDa), the nucleocapsid (NC, p3 of 34.9 kDa), and the putative movement protein (MP, p4 of 40.7 kDa), while p5 (55 kDa) and p6 (27 kDa) had unknown functions. All RNA segments showed distant relationships to viruses of the genus Emaravirus, and in particular to pigeonpea sterility mosaic virus (PPSMV), with which they shared nucleotide sequence identity ranging from 48.5 % (RNA3) to 62.5 % (RNA1). In phylogenetic trees constructed from the sequences of the proteins encoded by RNA1, RNA2 and RNA3 (p1, p2 and p3), this new viral entity showed a consistent grouping with fig mosaic virus (FMV) and rose rosette virus (RRV), which formed a cluster of their own, clearly distinct from PPSMV-1. In experimental greenhouse trials, this novel virus was successfully transmitted to pigeonpea and French bean seedlings by the eriophyid mite Aceria cajani. Preliminary surveys conducted in the Hyderabad region (India) showed that the virus in question is widespread in pigeonpea plants affected by sterility mosaic disease (86.4 %) but is absent in symptomless plants. Based on molecular, biological and epidemiological features, this novel virus is the second emaravirus infecting pigeonpea, for which the provisional name pigeonpea sterility mosaic virus 2 (PPSMV-2) is proposed.

In order from RNA1 to RNA6, accession numbers are: HF912243-HF912246, HG939489, HG939490.

Rabenstein, Frank's insight:

The recent finding of a new emaravirus (Wheat mosaic virus, formerly High Plains Virus, transmitted by Aceria tossichella)  with
eight RNA segments [40] raises questions about the number
of RNAs that compose an emaraviral genome

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Six-row Winter Barley Lancelot

The Lancelot variety is a late to semi-late six-row feeding winter barley. It was developed at the Breeding Station,
Lužany, SELGEN a.s. and registered in the Czech Republic in 2013. Lancelot has very good resistance to winter stresses in combination with resistance to BaMMV/BaYMV (Barley mild mosaic virus/Barley yellow mosaic virus) based on the gene rym4.
Keywords: Barley mild mosaic virus; Barley yellow mosaic virus; cultivar description; Hordeum vulgare L.; winter hardiness

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BMC Genomics | Abstract | The genome of Diuraphis noxia, a global aphid pest of small grains

Abstract (provisional)

Background The Russian wheat aphid, Diuraphis noxia Kurdjumov, is one of the most important pests of small grains throughout the temperate regions of the world. This phytotoxic aphid causes severe systemic damage symptoms in wheat, barley, and other small grains as a direct result of the salivary proteins it injects into the plant while feeding. Results We sequenced and de novo assembled the genome of D. noxia Biotype 2, the strain most virulent to resistance genes in wheat. The assembled genomic scaffolds span 393 MB, equivalent to 93% of its 421 MB genome, and contains 19,097 genes. D. noxia has the most AT-rich insect genome sequenced to date (70.9%), with a bimodal CpG(O/E) distribution and a complete set of methylation related genes. The D. noxia genome displays a widespread, extensive reduction in the number of genes per ortholog group, including defensive, detoxification, chemosensory, and sugar transporter groups in comparison to the Acyrthosiphon pisum genome, including a 65% reduction in chemoreceptor genes. Thirty of 34 known D. noxia salivary genes were found in this assembly. These genes exhibited less homology with those salivary genes commonly expressed in insect saliva, such as glucose dehydrogenase and trehalase, yet greater conservation among genes that are expressed in D. noxia saliva but not detected in the saliva of other insects. Genes involved in insecticide activity and endosymbiont-derived genes were also found, as well as genes involved in virus transmission, although D. noxia is not a viral vector. Conclusions This genome is the second sequenced aphid genome, and the first of a phytotoxic insect. D. noxia’s reduced gene content of may reflect the influence of phytotoxic feeding in shaping the D. noxia genome, and in turn in broadening its host range. The presence of methylation-related genes, including cytosine methylation, is consistent with other parthenogenetic and polyphenic insects. The D. noxia genome will provide an important contrast to the A. pisum genome and advance functional and comparative genomics of insects and other organisms.

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Virology Journal | Abstract | iTRAQ-based quantitative proteomics analysis of rice leaves infected by Rice stripe virus reveals several proteins involved in symptom formation

Abstract (provisional)

Background Rice plants infected by Rice stripe virus (RSV) usually leads to chlorosis and death of newly emerged leaves. However, the mechanism of RSV-induced these symptoms was not clear. Methods We used an iTRAQ approach for a quantitative proteomics comparison of non-infected and infected rice leaves. RT-qPCR and Northern blot analyses were performed for assessing the transcription of candidate genes. Results As a whole, 681 (65.8 % downregulated, 34.2 % upregulated infected vs. non-infected) differentially accumulated proteins were identified. A bioinformatics analysis indicated that ten of these regulated proteins are involved in chlorophyll biosynthesis and three in cell death processes. Subsequent RT-qPCR results showed that downregulation of magnesium chelatase was due to reduced expression levels of the genes encoding subunits CHLI and CHLD, which resulted in chlorophyll reduction involved in leaf chlorosis. Three aspartic proteases expressed higher in RSV-infected leaves than those in the control leaves, which were also implicated in RSV-induced cell death. Northern blot analyses of CHLI and p0026h03.19 confirmed the RT-qPCR results. Conclusions The magnesium chelatase and aspartic proteases may be associated with RSV-induced leaf chlorosis and cell death, respectively. The findings may yield new insights into mechanisms underlying rice stripe disease symptom formation.

The complete article is available as a provisional PDF. The fully formatted PDF and HTML versions are in production.
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Registration of ‘YZ05-51’ Sugarcane (moderate resistance to Sorghum mosaic virus and Sugarcane mosaic virus)

Abstract

‘YZ05-51’ (Reg. No. CV-161, PI 673444) sugarcane (a complex hybrid of Saccharum spp.) was developed through cooperative research conducted by the Yunnan Sugarcane Research Institute (YSRI) of Yunnan Academy of Agricultural Sciences, and Yunnan Yunzhe Technology Development Co. Ltd. It was released to growers in mainland China on 1 Aug. 2013. YZ05-51 was selected from the cross Yacheng 90-56 × ‘ROC 23’ planned by YSRI and crossed at Yacheng Sugarcane Breeding Station (YSBS) of the Guangzhou Sugar Industry Research Institute, Yacheng, Hainan Province of mainland China in January 2005. The female parent (Yacheng 90-56) is an advanced clone developed by YSBS. The male parent (ROC23) is a cultivar developed by the Taiwan Sugar Research Institute. YZ05-51 was selected from a five-stage selection program in YSRI and tested in the eighth China Regional Trial for Sugarcane Varieties at 14 locations in mainland China for 2 yr. YZ05-51 was released by the China Committee of Sugarcane Variety Release because of its higher cane yield compared with ROC16 and ROC22 (two reference cultivars) (7.1 and 1.1%, respectively), its higher sugar yield compared with ROC16 and ROC22 (10.6 and 2.7%, respectively), and its resistance to drought, high resistance to smut (caused by Ustilago scitaminea H. & P. Sydow), and moderate resistance to mosaic (Sorghum mosaic virus and Sugarcane mosaic virus).

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Viral Nanotechnology

Viral Nanotechnology | Cereal and grass viruses | Scoop.it
Viral Nanotechnology presents an up-to-date overview of the rapidly developing field of viral nanotechnology in the areas of immunology, virology, microbiology, chemistry, physics, and mathematical modeling. Its chapters are by leading researchers and practitioners, making it both a comprehensive and indispensable resource for study and research. The field of viral nanotechnology is new and quickly expanding due to increasing demand of the applications already developed. The editors identify viral nanotechnology as a significant science that concerns itself with how to use the molecular modules that the distinctly different science of molecular engineering only constructs. The current potential applications of viral technology are manifold, with opportunities to revolutionize practices in photonics, catalysis, electronics, energy, biomedicine, health care, and public health. This book emphasizes using viral nanotechnology to improve health. A special emphasis is placed upon using viral nanotechnology for developing vaccines. In addition, it documents viral nanotechnology’s use as a powerful tool for developing drugs and genetic therapies. There is also great potential in its use as a means for diagnostics, including the development of diagnostic reagents and novel imaging technologies for detecting disease and infectious agents. Viral nanotechnology’s rapid and exciting growth is due to the need for new tools in the prevention, diagnosis, and treatment of disease. The contributors to this volume approach each chapter with the hope that their research and practices will contribute to an improvement in health and life on an unprecedented scale in human history.
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Studies on Rice Breeding for Resistance to Virus Diseases Transmitted by the Green Leafhopper Spiecise(Nephotettix spp.)(ツマグロヨコバイ類が媒介するウイルス病に対するイネの抵抗性育種に関する研究)

Studies on Rice Breeding for Resistance to Virus Diseases Transmitted by the Green Leafhopper Spiecise(Nephotettix spp.)(ツマグロヨコバイ類が媒介するウイルス病に対するイネの抵抗性育種に関する研究) 井邊時雄 京都大学 1999-11-24
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Patent US20150089686 - Plant Germplasm Resistant to RNA Viruses

Disclosed is a dsRNA construct used to silencing specific eukaryotic translation initiation factor in plants to produce a plant resistant to viruses such as Potyviruses, Luteoviruses, and Furoviruses. More specifically, the plant would be resistant to viruses such as Wheat streak mosaic virus, Triticum mosaic virus, Soil bourne mosaic virus, or Barley yellow dwarf virus. Also disclosed are non-transgenic wheat plants having the genes for eIF(iso)4E-2 or eIF4G silenced.
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RNA polymerase slippage as a mechanism for the production of frameshift gene products in plant viruses of the Potyviridae family

RNA polymerase slippage as a mechanism for the production of frameshift gene products in plant viruses of the Potyviridae family | Cereal and grass viruses | Scoop.it
Publication » RNA polymerase slippage as a mechanism for the production of frameshift gene products in plant viruses of the Potyviridae family.
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TRANSMISSION OF DIGITARIA STREAK VIRUS BY THE MAIZE STREAK VIRUS LEAFHOPPER VECTO CICADULINA MBILA NAUDÉ

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Ecology and Epidemiology of Wheat streak mosaic virus, Triticum mosaic virus, and their mite vector in wheat and grassland fields

Ecology and Epidemiology of Wheat streak mosaic virus, Triticum mosaic virus, and their mite vector in wheat and grassland fields | Cereal and grass viruses | Scoop.it

Zusammenfassung

 

The Great Plains region serves as one of the most important areas for wheat production in the United States. This region, including Montana through Texas, produces approximately 59% of the U.S. wheat production. In the more southern and southwestern regions, winter wheat typically planted as a dual purpose crop for both cattle grazing and grain production. This system allows producers to earn extra income for grazing, however early fall planting also exposes the wheat to a variety of pests and pathogens. Some of the most important viral pathogens affecting wheat in this area are the mite-vectored viruses Wheat streak mosaic virus (WSMV), Triticum mosaic virus (TriMV), and Wheat mosaic virus (WMoV). Within this virus group, WSMV and TriMV are most commonly found during co-infection, which increases disease severity. These viruses are transmitted by the wheat curl mite, (WCM) Aceria tosichella, which relies on wind for passive movement from host to host. The WCM and viruses survive between wheat seasons on reservoir hosts such as volunteer wheat and some perennial and annual grasses. Management of these pathogens are mainly aimed at cultural control through destruction of alternative hosts and delayed planting. Many of these methods are outdated and have not been evaluated in the Texas High Plains. Therefore studies were conducted to examine the ecology and epidemiology of WSMV and TriMV by evaluating alternative host sources, time of vector movement during the year, and pathogen distribution within the host and vector. Native and introduced grasses, commonly found in CRP and rangeland plantings, were evaluated for potential to serve as alternative host reservoirs for WCM and WSMV and TriMV. Three fields classified as a CRP, rangeland, and an underdeveloped grassland field were evaluated for WCM population dynamics. Higher eriophyid mite population numbers, including the WCM, were detected in the underdeveloped field when compared to the CRP or rangeland fields. The underdeveloped field contained a large number of other grasses not found in CRP and rangeland plantings. Therefore to further examine CRP grasses for their ability to serve as alternative hosts, CRP grasses were infested by the WCM and inoculated with WSMV and TriMV. Grasses commonly planted in CRP fields did not serve as hosts for either the WCM or WSMV and TriMV. However, other grasses including western wheatgrass and rescuegrass were found to be hosts for the WCM but not WSMV or TriMV. To identify areas that pose a potential source for wheat virus disease, surveys were conducted on CRP, rangeland fields, and roadside areas adjacent or next to wheat production fields. All grass species found within each field and roadside site were identified as either hosts or non-host species for both the WCM and viral pathogens. CRP and rangeland fields contained low numbers of host grasses, except in the case of witchgrass, which was detected in 33% of CRP fields. However, roadside areas contained a large number of warm season hosts for both the WCM and WSMV and TriMV. Samples of witchgrasss, prairie grass, and barnyardgrass, collected from a single roadside location adjacent to volunteer wheat infected by WSMV and TriMV, tested positive for virus infection.. Roadside areas containing these and other warm season grasses were determined to be a more important sources of wheat viral disease. Studies were also conducted to evaluate the effectiveness of late planting as a tactic to reduce mite movement and pathogen spread from volunteer wheat. Movement of WCMs from the volunteer wheat during the winter months was detected even after delayed planting in October. Incidence of WSMV also was detected as early as December. These early infections resulted in reductions in grain yield that increased in proximity to the source point. Therefore, even delayed planting in the presence of volunteer wheat does not protect wheat against winter infection. Further studies examined co-infection of both WSMV and TriMV within host plants and the WCM along disease gradients. Incidence of co-infection with both WSMV and TriMV were found to be higher at the edge of the field, closest to the area of initial pathogen/vector spread. Co-infections decreased with distance into the field with single infections by WSMV continuing to a greater distance. Single infections of only TriMV were found in low incidence in both fields. WCMs also displayed differences in pathogen distribution. Field 1 contained a large percentage of mites carrying both WSMV and TriMV near the edge of the field. Field 2 contained lower numbers of co-viruliferous mites and no mites carrying TriMV only. Mites collected from co-infected wheat tillers were also examined for differences in WSMV and TriMV titer levels. Plants co-infected with both WSMV and TriMV contained higher levels of TriMV titer in both fields. However, mites collected from these tillers contained higher levels of WSMV than TriMV demonstrating preferential uptake of WSMV over TriMV. These findings help to illuminate pathogen distributions detected within fields containing co-infections of both WSMV and TriMV and higher transmission efficiencies of WSMV. Multiple aspects of WSMV and TriMV ecology and epidemiology were explored to evaluate management tactics involving CRP and alternative hosts, delayed planting to reduce infection incidence, and disease spread during co-infection by WSMV and TriMV. Grasses commonly used in CRP and rangeland fields do not serve as significant sources of WSMV and TriMV infection. However, roadside areas contain a variety of host grasses and could serve as a parietal risk for wheat disease. WCM populations are capable of movement even after delayed planting therefore strict volunteer control is need. Vector populations have an effect on disease distribution within fields containing co-infections of WSMV and TriMV due to preferential uptake of WSMV over TriMV. These factors need further exploration in the case of synergistic interactions between WSMV and TriMV.URIhttp://hdl.handle.net/2346/62348

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Reply to “New Zealand Stresses that It Is High Plains Virus Free, an the Virus Struggles with an Identity Crisis”

We thank Ochoa-Corona et al. for finding an inadvertent error
in our recent publication (1). We erroneously noted the
reported presence of Wheat mosaic virus (WMoV), also known as
High Plains virus (HPV), in New Zealand (1; see the Author Correction in this issue). Our statement was based on our misinterpretation of the detection of this pathogen in maize seed lots from the United States by scientists working in New Zealand (2). According to Lebas et al. (2), “neither the virus nor its vector is
present in New Zealand.” It should be noted, however, that the
vector, the wheat curl mite (Aceria tosichella, also known as Eriophyes tulipae), was reported in New Zealand 30 years ago (3),
though it is unclear whether permanent populations were established.
To our knowledge, there are no published reports of WoMV (HPV) in New Zealand. We sincerely regret this error.
The causal agent of High Plains disease was originally named
High Plains virus (4), which was later changed to Wheat mosaic
virus (WMoV) (5), as per the widely used conventions of the International Committee on Taxonomy of Viruses for naming new
taxa. To avoid further confusion, we simply followed Skare et al.’s
(5) proposed designation, WMoV, as the causal agent of High
Plains disease in our recent publication (1). Since the genome of
the causal agent of High Plains disease has been characterized
under the name WMoV (1) together with the fact that the name
WMoV was used in several recent publications (5–8), we encourage
the official adoption of WMoV as the causal agent of High
Plains disease to avoid a prolonged identity crisis for this virus.

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A study on the Effect of some cultural practices and insecticides in integrated management of Barley yellow dwarf viruses infecting barley

A study on the Effect of some cultural practices and insecticides in integrated management of Barley yellow dwarf viruses infecting barley | Cereal and grass viruses | Scoop.it
Barley yellow dwarf viruses affect many cereal crops, and can cause economic damage. To minimize damage, cultural practices such as planting date, plant densities and the use of insecticides were...
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Differential transmission of two isolates of Wheat streak mosaic virus by five wheat curl mite populations

Differential transmission of two isolates of Wheat streak mosaic virus by five wheat curl mite populations | Cereal and grass viruses | Scoop.it

Wheat streak mosaic virus (WSMV), type member of the genus Tritimovirus in the family Potyviridae, is an economically important virus causing annual average yield losses of approximately 2-3% in winter wheat across the Great Plains. The wheat curl mite (WCM), Aceria tosichella, transmits WSMV along with two other viruses found throughout the Great Plains of the United States. Two common genotypes of WSMV (‘Sidney 81’ and ‘Type’) in the U.S. share 97.6% nucleotide sequence identity, but their transmission relationships with the wheat curl mite are unknown. The objective of this study was to determine transmission of these two isolates of WSMV by five WCM populations (‘Nebraska’, ‘Montana’, ‘South Dakota’, ‘Type 1’ and ‘Type 2’). Non-viruliferous mites from each population were reared on wheat source plants mechanically inoculated with either Sidney 81 or Type WSMV isolates. For each source plant, individual mites were transferred to 10 separate test plants and virus transmission was determined by a DAS-ELISA assay. Source plants were replicated 9 times for each treatment (90 individual mite transfers). Results indicate that three mite populations transmitted Sidney 81 at higher rates compared to Type. Two mite populations (Nebraska and Type 2) transmitted Sidney 81 and Type at higher rates compared to the other three populations. Results from this study demonstrate that interactions between virus isolates and mite populations influence the epidemiology of WSMV.

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Effects of aphid feeding and associated virus injury on grain crops in Australia - Austral Entomology - Wiley Online Library

Effects of aphid feeding and associated virus injury on grain crops in Australia -  Austral Entomology - Wiley Online Library | Cereal and grass viruses | Scoop.it

Abstract

We review yield effects caused by aphid feeding and associated virus injury to cereal, oilseed and pulse crops, and estimate the potential economic loss caused by aphids in Australia. Potential yield reduction due to aphids was determined through a survey of quantitative data from experiments that assessed aphids' effect on grain yield. In cereals, four aphids caused damage; on barley, feeding injury caused by Rhopalosiphum padi + Rhopalosiphum maidis was most damaging in terms of yield reduction (25.5%) with an economic loss of $19/ha. Barley yellow dwarf virus transmitted by R. padi + Sitobion miscanthi was more damaging than direct feeding, causing a yield reduction of 39% and economic loss of $21/ha for wheat. On canola, beet western yellow virus transmitted by Myzus persicae caused the highest yield reduction of 34% and economic loss of $115/ha, although this was measured through artificial inoculations. Feeding injury was high in Brevicoryne brassicae which caused an average yield reduction of 34% and associated economic loss of $88.5/ha, while Lipaphis erysimi and M. persicae had negligible economic effects but more data are needed. On pulses, the most economically damaging (unidentified) aphids feeding on lupins caused a yield reduction of 43% and economic loss of $24/ha. The aphids M. persicae + Aphis craccivora + Acyrthosiphon kondoi reduced lupin yields by 13% and economic returns by $7.40/ha. On field peas, a 14% reduction in yield was caused by transmitted viruses such as pea seed-borne mosaic virus which caused economic losses of $20.50/ha. In total, feeding and virus injuries resulted in potential economic costs of $241 and $482 million/year, respectively. Although this review provides estimates of potential yield and economic losses due to aphids, few data were available for some crops, aphid species or regions (e.g. oats). Nevertheless, economic costs associated with aphids appear substantial.

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