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Texas: Wheat Streak Mosaic Focus of Research Grant » Blog Archive

Texas: Wheat Streak Mosaic Focus of Research Grant » Blog Archive | Cereal and grass viruses | Scoop.it
The grant will help researchers update 1950s and 1960s technology and methods currently used to control mites and diseases they transmit.
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Identification, prevalence and impacts of viral diseases of UK winter wheat - Nottingham ePrints

Identification, prevalence and impacts of viral diseases of UK winter wheat - Nottingham ePrints | Cereal and grass viruses | Scoop.it

Abstract

 

The potential for viruses to be causing the plateau in the yield of UK wheat (Triticum aestivum) was investigated. Mechanical inoculation of Cynosurus mottle virus to wheat cv. Scout and cv. Gladiator caused 83% and 58% reduction in the number of grains produced, highlighting the potential of viruses to cause disease and yield loss. Viruses historically detected in cereals in the UK were not found to be prevalent following real time reverse transcriptase polymerase chain reaction testing of 1,356 UK wheat samples from 2009-2012 using eleven assasys developed in the project. This included an assay for Cynosurus mottle virus, which was based on its complete genome sequence which was obtained for the first time in this project. Viruses detected were Barley yellow dwarf virus-MAV (6 samples) (BYDV-MAV), Barley yellow dwarf virus-PAV (6 samples) (BYDV-PAV) and Soil-borne cereal mosaic virus (12 samples) (SBCMV). There was a higher prevalence of viruses in the south, thought to be due to warmer temperatures which benefitted insect vectors and the molecular processes of infection. Viruses were most commonly detected in the variety JB Diego, perhaps because this variety has no known resistance to viruses.
The low prevalence of known viruses could also have been because they were outcompeted or replaced by previously unknown ones. Next generation sequencing was used to test 120 samples from an organic site, including wheat, weeds and insects, to search for novel viruses. Testing of twelve storage regimes for insect traps using BYDV-PAV infected Sitobion avenae for recovery of PCR amplifiable RNA using 18S rRNA and BYDV-PAV assays found that 0.5 M EDTA was the most successful regime which was therefore used in the collection of samples for sequencing. Known viruses such as BYDV-PAV were detected along with some additional potentially novel viruses (eight possibly novel viruses or strains of viruses with four in wheat). One such virus was apparently present in 25% of all wheat samples tested, making it potentially very significant. This could be important for unlocking the yield potential of wheat because it could be a cryptic virus which is highly prevalent. In order to control the spread of viruses their methods of transmission must be understood, therefore testing of seeds and resulting plants from Cynosurus mottle virus infected material was done. Tests did not detect the virus, therefore it was concluded that seed transmission does not occur. However, further tests are required. In conclusion this study indicates that known viruses are not currently a major problem for UK winter wheat. However, novel viruses that are a problem may be detected in the future perhaps by next generation sequencing. Additonal viruses from abroad would add to the threat. The impact of all viruses in wheat may be greater in the future due to climate change.

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Helping wheat defend itself against damaging viruses

Helping wheat defend itself against damaging viruses | Cereal and grass viruses | Scoop.it
Wheat diseases caused by a host of viruses that might include wheat streak mosaic, triticum mosaic, soil-borne mosaic and barley yellow dwarf could cost producers 5 to 10 percent or more in yield reductions per crop, but a major advance in developing broad disease-resistant wheat is on the horizon.
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Development of a Wireless Computer Vision Instrument to Detect Biotic Stress in Wheat

Development of a Wireless Computer Vision Instrument to Detect Biotic Stress in Wheat | Cereal and grass viruses | Scoop.it
Knowledge of crop abiotic and biotic stress is important for optimal irrigation management. While spectral reflectance and infrared thermometry provide a means to quantify crop stress remotely, these measurements can be cumbersome. Computer vision offers an inexpensive way to remotely detect crop stress independent of vegetation cover. This paper presents a technique using computer vision to detect disease stress in wheat. Digital images of differentially stressed wheat were segmented into soil and vegetation pixels using expectation maximization (EM). In the first season, the algorithm to segment vegetation from soil and distinguish between healthy and stressed wheat was developed and tested using digital images taken in the field and later processed on a desktop computer. In the second season, a wireless camera with near real-time computer vision capabilities was tested in conjunction with the conventional camera and desktop computer. For wheat irrigated at different levels and inoculated with wheat streak mosaic virus (WSMV), vegetation hue determined by the EM algorithm showed significant effects from irrigation level and infection. Unstressed wheat had a higher hue (118.32) than stressed wheat (111.34). In the second season, the hue and cover measured by the wireless computer vision sensor showed significant effects from infection (p = 0.0014), as did the conventional camera (p < 0.0001). Vegetation hue obtained through a wireless computer vision system in this study is a viable option for determining biotic crop stress in irrigation scheduling. Such a low-cost system could be suitable for use in the field in automated irrigation scheduling applications.
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Study on the Function of P8 Protein of Rice gall dwarf virus in Viral Assembly by RNAi

Abstract 

 

Rice gall dwarf virus (RGDV) is a member of the genus Phytoreovirus in the family Reoviridae, which is transmitted by leafhopper Recilia dorsalis and Nephotettix cincticeps in a persistent-propagative manner. The viral genome of RGDV encodes 6 structural proteins and 6 nonstructural proteins. The structural protein P8 is a component of viral outer capsid protein, but the function of this protein in viral infection in insect vector is still unknown. Here, RNA interference (RNAi) induced by double-stranded RNA(dsRNA) synthesized in vitro was used to investigate the role of RGDV P8 protein in viral infection in the cultured cells derived from R. dorsalis. Immunofluorescence assay of RGDV infection in cultured cells after the treatment of dsRNAs from P8 gene (dsP8) howed that dsP8 did not only knock down the expression of P8, but also reduced the accumulation of RGDV in the insect vector cells. Then viral dsRNA genome and proteins were detected by SDS-PAGE and Western blot, the results indicated that the treatment of dsP8 significantly decreased the synthesis of viral dsRNA genome and the expression of P8 protein in insect vector cells. Thus, the results suggested that structural protein P8 of RGDV might play a role in viral assembly and multiplication in insect vector cells. This provides important theoretical basis for controling the spreading of rice gall dwarf disease by using RNAi technology.

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Knockdown of Nonstructural Protein(Pns12) of Rice gall dwarf virus(RGDV) Inhibits Viral Replication in Insect Vector Cells

Abstract 

 

Rice gall dwarf virus(RGDV), the genus Phytoreovirus in the family Reoviridae, is transmitted by the leafhopper vector(Recilia dorsalis) in a persistent-propagative manner. Nonstructural protein(Pns12), encoded by segment 12 of RGDV, is one of the components of viroplasm which is the site for viral replication and assembly of progeny virons during viral infection in its insect vector cells. In this study, to investigate the functional role of Pns12 in the formation of viroplasm in its insect vector cells, the polyclonal antibody against Pns12 was prepared and purified, then conjugated to fluorescein isothiocyanate. The immunoglobulin G(IgG) of P8 was purified and conjugated to rhadamine. Immunofluorescence microscopy demonstrated that Pns12 antibodies specifically distributed in the viroplasm matrix during RGDV infection in the vector cells in monolayers (VCMs), while outer capsid protein P8 were accumulated at the periphery of the viroplasm. The viroplasm increased in size over time. Knockdown of Pns12 by RNA interference (RNAi) induced by dsRNAs, targeting Pns12 gene of RGDV, significantly inhibited the formation of viroplasm compared with dsGFP, suggesting that RGDV replication was inhibited. Western blot showed that viral Pns12 and P8 expression reduced in the VCMs treated with dsPns12. Thus, the present study indicated that Pns12 of RGDV played an important role in viroplasm formation and viral replication in its insect vector cells. RNAi induced by dsRNAs derived from the viral genes of viroplasm matrix protein may be an ideal tool for inhibiting the infection and transmission of RGDV by leafhopper vectors.

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Comparison Study of Two Different Isolation and Purification Method for Rice Tungro Bacilliform Virus (RTBV)

Abstract

This paper studies two different virus purification methods for rice tungro bacilliform virus. In the first method, infected samples were extracted using liquid nitrogen with mixture of 10% Cellulases whereas the second method used alternate spinning of the infected samples at high and low speed with 5% Cellulases. Viral particles from both methods were examined by transmission electron microscopy (TEM) and rod-shaped with rounded ends was only seen on samples that were extracted with method 2. The estimated purity and concentration of method 2 is higher compare to method 1 which are 1.362 and 1.608 mg/ml and 0.958 and 0.299 mg/ml respectively.

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A Novel Itera-Like Densovirus Isolated by Viral Metagenomics from the Sea Barley Hordeum marinum

ABSTRACT

Densoviruses (DVs) infect arthropods and belong to the Parvoviridae family. Here, we report the complete coding sequence of a novel DV isolated from the plant Hordeum marinum (Poaceae) by viral metagenomics, and we confirmed reamplification by PCR. Phylogenetic analyses showed that this novel DV is related to the genus Iteradensovirus.

Previous SectionNext SectionGENOME ANNOUNCEMENT

Densoviruses (DVs) are small nonenveloped icosahedral viruses infecting arthropods, including pests and vectors for which they are considered biocontrol agents. They contain a single-strand linear DNA genome ranging from 4 to 6 kb, ended by inverted terminal repeats (ITRs) (1). Only 15 DV species are referenced in GenBank so far (2); they display a large diversity of sequences, structures, and organizations. Such diversity, together with the diversity of their invertebrate hosts, suggests that DVs are largely unknown and ubiquitous in the environment. It is crucial to understand the densovirus diversity and prevalence for both fundamental and applied virology issues.

A novel densovirus was detected from sea barley (Hordeum marinum) using a virion-associated nucleic acid (VANA) viral metagenomic approach (3). To complement this genome, we performed Rapid Amplification of cDNA Ends (RACE) (Roche), and the products were cloned in the pGEM-T Easy Vector (Promega) and sequenced. The sequences were assembled using Geneious 7.1.4 and compared to database sequences using BLASTn, BLASTp, and tBLASTx (4). The results were considered to be indicative of significant homology when BLAST E values were <10−3. The genome of this novel DV consists of 4,734 nucleotides (nt), with short ITRs of 130 and 77 nucleotides (nt) at the 3′ and 5′ ends, respectively. The iteravirus genome size is about 5 kb, with ITRs of 250 nt, suggesting that the ITRs of this novel densovirus are not complete (5). The genomic organization of this densovirus is monosense, with three predicted intronless open reading frames (ORFs) encoding two nonstructural proteins (NS) and one structural protein (VP). ORF1 (nt 253 to 2505) has a coding capacity of 750 amino acids (aa) and contains the typical nonstructural 1 (NS1) helicase superfamily III. ORF2 (nt 2559 to 4568) encodes a 669-aa protein corresponding to VP, and it contains the characteristic phospholipase A2 motif (6). ORF3 (nt 380 to 1729) has a coding capacity for NS2 of 449 aa and typically overlapped NS1. The alignment of the VP and NS protein sequences using Clustal W 1.8.1 (7) revealed that this genome had the highest identity (84.9%) with Danaus plexippus plexippus densovirus (DpplDV) (GenBank accession no. KF963252) (8). This genome was independently purified from leaves of the original plant stored at −80°C (Qiagen plant DNeasy kit). The PCR products were obtained from different leaves using 15 pairs of primers covering the whole genome that were sequenced using Sanger’s method (Cogenics). Recombination analyses using RDP4.18 (9) revealed that this novel DV might result from an intragenus recombination event between DpplDV and Dendrolimus punctatus densovirus (DpDV).

No insect has been found in any part of this plant, no reads obtained from this plant were assigned to arthropods, and no products were obtained using an insect DNA bar coding based on the PCR amplification of a fragment of the mitochondrial cytochrome c oxidase subunit I gene (10). This densovirus might come from contamination of the plant aerial part by infected arthropods or circulate systemically in planta, as already reported (11). This virus was tentatively named H. marinum densovirus (HormaDV).

Nucleotide sequence accession number.The GenBank accession no. of HormaDV is KM576800.

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Since the genome encodes for one structural protein (VP = a 669 aa protein) it would be interesting to see weather virus particles are formed in that plant.

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Rice Tungro Disease: From Identification to Disease Control

Abstract: As the most devastating viral disease of rice in South and Southeast Asia, rice tungro disease
remains one of the significant fears to sustainable annual rice productions in the world. Due to the increasing
world population and subsequent increase in demand for food, identifying the causal agents and symptoms
of disease and the methods of disease management are key to understanding how to reduce the economic
damage caused by rice pathogens. In this review, we described the current state of knowledge of rice tungro
disease caused by two morphologically and genomically dissimilar viruses: Rice tungro bacilliform virus
and Rice tungro spherical virus. This includes genome structure, transmission, symptoms, diagnostic
methods and biological control of the disease.

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Seasonal occurrence of Laodelphax striatellus (Hemiptera: Delphacidae) in a rice-forage crops mixed cropping area in central Kyushu, Japan - Springer

Seasonal occurrence of Laodelphax striatellus (Hemiptera: Delphacidae) in a rice-forage crops mixed cropping area in central Kyushu, Japan - Springer | Cereal and grass viruses | Scoop.it

Abstract

The small brown planthopper, Laodelphax striatellus (Fallén) is an important pest of rice in East Asia because it is a vector of rice stripe virus. In this study, we examined the seasonal occurrence of L. striatellus in an agricultural area in central Kyushu in which cropping systems have been changing since the 1970s. The first generation of L. striatellus emerged in the spring, not only on barley, oats, and Italian ryegrass but also on spring crops of forage maize. The second generation of L. striatellus adults emerged in forage maize fields in July, after harvesting of winter crops of barley, oats, and Italian ryegrass. These results suggest that spring crops of forage maize are important hosts of L. striatellus from spring to early summer. The overwintering generation of L. striatellus was collected from rice ratoon, suggesting this is a favorable host for L. striatellus during winter. The appearance of these novel hosts may be a factor in the recent re-emergence of L. striatellus in central Kyushu.

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L. striatellus is also known vector of Rice stripe virus.

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A Top Ten list for economically important plant viruses - Online First - Springer

A Top Ten list for economically important plant viruses - Online First - Springer | Cereal and grass viruses | Scoop.it
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Ed Rybickis Plant Virus Top Ten includes several cereal infecting viruses and is, in alphabetical order as follows:

 

• African cassava mosaic disease (ACMD) begomovirus
complex
• Banana bunchy top nanovirus (BBTV)
• Banana streak badnavirus (BSV)
• Barley yellow dwarf disease luteovirus complex
• Cucumber mosaic cucumovirus
• Maize streak mastrevirus (MSV)
• Maize dwarf mosaic/Sugarcane mosaic potyviruses
• Rice tungro disease complex
• Rice yellow mottle sobemovirus (RYMV)
• Sweet potato feathery mottle potyvirus (SPFMV)

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Efficient Inoculation of Rice black-streaked dwarf virus to Maize Using Laodelphax striatellus Fallen - Miao - 2014 - Journal of Phytopathology - Wiley Online Library

Efficient Inoculation of Rice black-streaked dwarf virus to Maize Using Laodelphax striatellus Fallen - Miao - 2014 - Journal of Phytopathology - Wiley Online Library | Cereal and grass viruses | Scoop.it
Abstract

Maize rough dwarf disease caused by Rice black-streaked dwarf virus (RBSDV) is the most important disease of maize in China. Although deploying disease resistant hybrids would be the most effective way to control the disease, development of resistant hybrids has been limited by virus transmission rates that are too low for effective screening. An efficient inoculation technique for RBSDV was developed using Laodelphax striatellus Fallen, in which a virus-free planthopper colony was developed and viruliferous planthoppers were obtained by allowing a 3- to 4-day acquisition access period on RBSDV-infected wheat plants. Planthoppers were then allowed a 25- to 28-day latent period on wheat seedlings followed by a 3-day inoculation access period on two-to-three-leaf stage maize seedlings. By 35 days postinoculation, susceptible hybrid ‘Zhengdan 958’, inbred lines of ‘Ye 107’ and ‘Ye 478’ plants showed 100% RBSDV infection with symptoms of stunting plants, darkening leaves and white waxy swellings on underside of leaves. At tasseling stage, average disease indices were from 96.4 to 100.0%. Enzyme-linked immunosorbent assays were correlated with the presence of symptoms. The high efficiency of RBSDV transmission obtained using this technique provides a reliable procedure to screen for RBSDV resistance in maize.

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Abstract: BARE, a Multiply Mobile Retrotransposon (Plant and Animal Genome XXIII Conference)

Date: Sunday, January 11, 2015
Time: 3:18 PMRoom: Golden Ballroom Alan H. Schulman , LUKE & University of Helsinki, Helsinki, Finland Marko Jääskeläinen , Institute of Biotechnology, University of Helsinki, Helsinki, Finland Wei Chang , Institute of Biotechnology, University of Helsinki, Helsinki, Finland Carlos M. Vicient , Center for Research in Agrigenomics CRAG (CSIC-IRTA-UAB-UB), Barcelona, Spain Eva Gómez-Orte , CIBIR (Centre for Biomedical Research of La Rioja), Logroño, Spain Jaakko Tanskanen , LUKE & University of Helsinki, Helsinki, Finland Retrotransposons are ubiquitous and abundant transposable elements in eukaryotic genomes. They are responsible for much of the variation in monoploid genome size over evolutionary time and have direct or indirect effects on genes by both insertional mutagenesis and epigenetic mechanisms. Over 74% of the large (5.1 Gb) barley genome is comprised of long terminal repeat (LTR) retrotransposons. Retrotransposon copies may be passed to the next generation by one of two ways: replication of existing copies as part of the chromosome; synthesis and propagation of new copies by the combined activities of RNA polymerase II and reverse transcriptase by a “copy and paste” life cycle virtually identical to that of retroviruses, excepting (so far as has been directly demonstrated) the ability to readily move from organism to organism infectively. The retrotransposon life cycle within the cell involves both nuclear and cytoplasmic phases. Integrated copies are transcribed within the nucleus, but translation and virus-like particle assembly takes place in the cytoplasm. Following replication, the cytoplasmic, packaged cDNA copies need to be brought back into the nucleus for integration of new copies to occur. We are interested in analyzing the intracellular trafficking of retrotransposon components, using the BARE retrotransposon family of barley as the model system. The goal is to develop an understanding of the mechanisms controlling the propagation of retrotransposons and consequences for the genome and plant.
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K-State research may halt spread of four wheat viruses | Baking Business | Baking Industry News and Opinions

K-State research may halt spread of four wheat viruses | Baking Business | Baking Industry News and Opinions | Cereal and grass viruses | Scoop.it
Baking industry news and commentary offering insight on business, new products, regulatory, market and product trends, supplier innovations and more.

 

“Yield loss due to wheat streak mosaic virus equaled more than 4,250,000 bus in the 2013 Kansas wheat crop alone, adding up to a $32,600,000 economic impact,” the Kansas Wheat Commission said.

 

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Resistance identification of rice cultivars to southern rice black-streaked dwarf disease in Guangxi. - CAB Direct

Objective: The resistance of rice cultivars for production to southern rice black-streaked dwarf disease (SRBSDD) in Guangxi was evaluated to provide references for integrated control of SRBSDD. Method: Mass inoculation was used for rice resistance evaluation to SRBSDD in this research. The tested rice cultivars included 45 main rice cultivars and 53 native rice cultivars in market of Guangxi. ...
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Assembly of viroplasms by viral nonstructural protein Pns9 is essential for persistent infection of rice gall dwarf virus in its insect vector

Highlights•

Infection route of RGDV in its insect vector is revealed.

RGDV spread directly from the initially infected epithelial cells of insect intestine toward the visceral muscle tissues.

Assembly of viroplasms by nonstructural protein Pns9 is essential for persistent infection of RGDV in vector.

Abstract

Rice gall dwarf virus (RGDV), a plant reovirus, is transmitted by leafhopper vector Recilia dorsalis in a persistent-propagative manner. In a sequential study of RGDV infection of its insect vector, the virus initially infected the filter chamber epithelium, then directly crossed the basal lamina into the visceral muscles, from where it spread throughout the entire midgut and hindgut. Finally, RGDV spread into the salivary glands. During RGDV infection of the continuous cultured cells of R. dorsalis, viroplasm that was mainly comprised of viral nonstructural protein Pns9 was formed and acted as the site of viral replication and assembly of progeny virions. Knockdown of Pns9 expression in cultured insect vector cells using synthesized dsRNAs from the Pns9 gene strongly inhibited viroplasm formation and viral infection. The microinjection of dsRNAs from the Pns9 gene strongly abolished viroplasm formation in the initially infected filter chamber epithelium and prevented viral spread into leafhopper visceral muscles. These results indicated that the assembly of viroplasms was essential for the persistent infection and spread of RGDV in its insect vector.

KeywordsRice gall dwarf virus;Leafhopper vector;Viral infection route;Pns9 protein;Viroplasm formation;RNA interference
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Identification and profiling of conserved and novel microRNAs in Laodelphax striatellus in response to rice black-streaked dwarf virus (RBSDV) infection

bstract

MicroRNAs (miRNAs) are small non-coding endogenous RNA molecules that play important roles in various biological processes. This study examined microRNA profiles of Laodelphax striatellus using the small RNA libraries derived from virus free (VF) and rice black-streaked dwarf virus (RBSDV) infected (RB) insects. A total of 59 mature miRNAs (46 miRNA families) were identified as conserved insect miRNAs in both VF and RB libraries. Among these conserved miRNAs, 24 were derived from the two arms of 12 miRNA precursors. Nine conserved L. striatellus miRNAs were up-regulated and 12 were down-regulated in response to RBSDV infection. In addition, a total of 20 potential novel miRNA candidates were predicted in the VF and RB libraries. The miRNA transcriptome profiles and the identification of L. striatellus miRNAs differentially expressed in response to RBSDV infection will contribute to future studies to elucidate the complex miRNA-mediated regulatory network activated by pathogen challenge in insect vectors.

KeywordsMicroRNA (miRNA);Laodelphax striatellus;Rice black-streaked dwarf virus (RBSDV);Deep sequencing
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Quantitative Trait Loci Mapping and Molecular Breeding for Developing Stress Resilient Maize for Sub-Saharan Africa

Abstract

The International Maize and Wheat Improvement Center (CIMMYT), in partnership with several public and private institutions, is working to develop and deploy improved maize (Zea mays L.) germplasm that is drought tolerant, nitrogen use efficient (NUE), and disease resistant for sub-Saharan Africa (SSA), using conventional pedigree selection and molecular breeding. Here, we provide an overview of the progress made on (i) quantitative trait loci (QTL) analysis for drought, NUE, and maize lethal necrosis (MLN); (ii) development of production markers for maize streak virus (MSV) and MLN resistance; and (iii) marker-assisted recurrent selection (MARS) and genomic selection (GS) for developing drought tolerant maize germplasm. We identified several small to moderate effect QTL associated with grain yield and anthesis-silking interval under low N, managed drought, and optimum environments, but only a few small to moderate effect QTL were detected in multiple genetic backgrounds. Thus, CIMMYT is conducting the largest public MARS and GS projects in SSA. A recent comparative study of pedigree selection, MARS and GS undertaken across 8 to 10 bi-parental populations, demonstrated the superior performance of both MARS and GS schemes over pedigree selection. More than 90% of current commercial maize germplasm was found to be highly susceptible to MLN disease. Preliminary mapping studies identified three major QTL for MLN disease resistance, and two are being used for pilot line conversion using marker-assisted backcrossing (MABC). For MSV, pilot marker-assisted selection is ongoing, using three single nucleotide polymorphic (SNP) markers to select a major QTL on chromosome 1. Development of drought tolerant and NUE maize varieties must include MLN resistance in eastern Africa, and we strongly suggest to maize breeders to introgress promising genomic regions for MLN resistance using either conventional or molecular methods.

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"Сельскохозяйственная биология": 5-2014 Гнутова

"Сельскохозяйственная биология": 5-2014 Гнутова | Cereal and grass viruses | Scoop.it

DIVERSITY OF PLANT VIRUSES IN THE EAST-ASIAN RUSSIA: 50 YEARS OF STUDYING

R.V. Gnutova

In ornamental plants, vegetables, fruits, berries, cereals and legumes the viral infections causes a decrease of productivity and yield quality, especially in the southern regions of agriculture in the Russian Far East where an infectious background is one of the highest. Besides, the viral infection leads to more impact from other phytopathogens, particularly under bacterial and fungal infections, and provokes degradation of varieties. Breeding varieties and hybrids resistant to viruses is now considered the most effective approach to antiviral plant protection. Therefore, the characteristic features of viruses are the key factors for plant protection strategy. For more than 50 years, in the Asian Russia more than 50 viruses have been found in agrocoenoses of vegetables, cereals, legumes, ornamental plants, berries and potato plants, and also in biocoenoses of wild plants and weeds. More than 10 of them have not been identified earlier not only in Far East and Siberia, but also in Russia. Basin on biological traits, physicochemical properties of viral polypeptides and nucleic acids, as well as antigenic characteristics of capsid proteins, a taxonomic status of the Asian Russian viral isolates has been identified, and their areal, pathogenicity and the impact have been studied. In Far East Russia, there have been revealed, described and identified the following viruses: Brome mosaic virus,Vicia unijuga mosaic virus, Alfalfa mosaic virus, Cucumber mosaic virus IA and IB East-Asian isolates, Soybean stunt virus, Tomato aspermy virus, Cauliflower mosaic virus Far-East Russianisolates, Dahlia mosaic virus, Radish mosaic virus type isolate, Red clover mottle virus, Arabis mosaic virus, Raspberry ringspot virus, Tobacco ringspot virus, Tomato ringspot virus, Potato leafrole virus, Barley yellow dwarf virus — PAV, Pea enation mosaic virus 1, Bean common mosaic virus, Bean yellow mosaic virus,Dahlia mild green mottle virus, Hippeastrum mosaic virus, Onion yellow dwarf virus, Potato virus A, Potato virus Y, Soybean mosaic virus, Tobacco etch virus, Tradescantia mosaic virus,Trifolium montanum (сlover) mosaic virus, Turnip mosaic virus, Watermelon mosaic virus (WMW-W),Cereal (Oat) Russian pupation (pseudo-roset) virus, Northern cereal mosaic virus, Lily symptomless virus, Potato virus M, Potato virus S,Vicia pseudorobus mosaic virus, Hydrangea ringspot virus, Plantago asiatica mosaic virus, Potato aucuba mosaic virus, Potato virus X, White clover mosaic virus,Tobacco necrosis virus,Rice stripe virus, Tobacco rattle virus, Tobacco mosaic virus, Tomato mosaic virus, Cucumber green mottle mosaic virus, Barley stripe mosaic virus,Rice mottle virus, Grapevine plum line virus, Pea streak virus, Potato yellow dwarf virus, Carnation ringspot dianthovirus, Carnation mottle virus. A few of them (marked as ordinary typed) are not still registered and entered into the list of International Committee on Taxonomy of Viruses (http://www.ncbi.nlm.nih.gov/ICTVdb/ICTVdB/). Using routine and molecular methods, the isolates were attributed to 18 genera from 10 families of 87 genera and 20 families described presently. Considering distance of Far East from the Central Russia, specific ecological factors, the local climate and unstable weather, a strategy for phytomonitoring of plant viruses has been worked out. In the southern and central zones, the most attention was paid to viruses on rice and soybean plants. The phytomonitoring of potato, vegetable plants and other crops was carried out all over the Asian Russia in both field conditions and greenhouses.

Keywords: plant viruses, methods of identification, taxonomy, East-Asian territory of Russia.

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In order to download the complete paper go to http://www.agrobiology.ru/articles/5-2014gnutova-eng.pdf

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The population genetics of maize dwarf mosaic virus in Spain - Springer

The population genetics of maize dwarf mosaic virus in Spain - Springer | Cereal and grass viruses | Scoop.it
Abstract

The population genetics of maize dwarf mosaic virus (MDMV) in Spain was assessed by analysis of the P1-HC region. Restriction fragment length polymorphism analysis of 363 isolates revealed that the MDMV population consisted of 69 haplotypes. Sequence analysis of 112 isolates confirmed a high degree of nucleotide sequence diversity (0.143), which was higher for P1 than for the HC. Twelve sequences showed a single different recombination event. Selection pressure analysis revealed that the P1-HC region was under strong negative selection. The MDMV population was spatially structured but not structured temporally or by host. Phylogenetic analysis split the sequences into five major groups.

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Seasonal occurrence of Laodelphax striatellus in Spain: Effect on the incidence of Maize rough dwarf virus

Abstract

Maize rough dwarf virus (MRDV) has emerged as a major constraint to maize crop production in Spain. The seasonal abundance of planthopper-vectored MRDV was studied during two consecutive years in trials located within the area with the highest incidence of MRDV. Insect density was estimated once every 15 days during the maize growing season using sticky and suction traps. Laodelphax striatellus Fallén was the sole planthopper present in these maize trials and 52% of the captured hoppers contained MRDV. The population of L. striatellus showed two peaks during the season; one in June and the other in September. Adults of L. striatellus were captured from mid-May to the beginning of October and viruliferous insects were captured from 18th May to the beginning of September. Levels of the incidence of MRDV were correlated with the first detection of planthoppers (whether carrying the virus or not) in maize fields during the early development stages of the crop, but not with the planthopper abundance. The data obtained in this study support that early sowing of maize could contribute to reduce the incidence of MRDV in the northeast of Spain.

Highlights

► MRDV has emerged as a major constraint to maize production in Spain. ► Virus diseases transmitted propagatively are strictly linked to its vectors. ► Laodelphax striatellus was the sole vector of MRDV. ► The MRDV incidence was correlated to first detection L. striatellus in maize fields. ► Early sowing maize could contribute to reduce MRDV incidence.

KeywordsMRDV;Vector;Planthoppers;Laodelphax
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Rice Stripe Tenuivirus p2 may Recruit or Manipulate Nucleolar Functions through an Interaction with Fibrillarin to Promote Virus Systemic Movement - Zheng - Molecular Plant Pathology - Wiley Online...

Rice Stripe Tenuivirus p2 may Recruit or Manipulate Nucleolar Functions through an Interaction with Fibrillarin to Promote Virus Systemic Movement - Zheng - Molecular Plant Pathology - Wiley Online... | Cereal and grass viruses | Scoop.it

Keywords: Rice stripe virus; Nucleolus; Fibrillarin; Systemic movement

 

Summary

Rice stripe virus (RSV) is the type species of the genus Tenuivirus and represents a major viral pathogen affecting rice production in East Asia. In this study, RSV p2 was fused to yellow fluorescent protein (p2 : YFP) and expressed in epidermal cells of Nicotiana benthamiana. p2 : YFP fluorescence was found to move to the nucleolus initially but leave the nucleolus for the cytoplasm forming numerous distinct bright spots there at later time points. A bimolecular fluorescence complementation (BiFC) assay showed that p2 interacted with fibrillarin and the interaction occurred in the nucleus. Both nucleolar localization and cytoplasmic distribution of p2 : YFP fluorescence were affected in fibrillarin silenced N. benthamiana. Fibrillarin depletion abolished the systemic movement of RSV but not that of Tobacco mosaic virus (TMV) and Potato virus X (PVX). A Tobacco rattle virus (TRV)-based virus induced gene silencing (VIGS) method was used to diminish RSV NS2 (encoding p2) or NS3 (encoding p3) during RSV infection. Silencing of NS3 alleviated symptom severity and reduced RSV accumulation but had no obvious effects on virus movement and the timing of symptom development. However, silencing of NS2 abolished systemic movement of RSV. The possibility that RSV p2 may recruit or manipulate nucleolar functions to promote virus systemic infection is discussed.

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Phylogenetic analysis of coat protein gene of CYDV-RPV strain from Wheat | Zamurrad |

Abstract

 

Background: Keeping in view the potential damage caused by viruses to production of different crops and possible ‘directed damages’ by manipulated viral attack in/across border collectively make phylogenetic analysis of any attacking viral specie important. Cereal yellow dwarf viruses (CYDV) are highly important viruses in wheat causing significant yield loss.

 

Methods: Double antibody sandwich ELISA and reverse transcription polymerase chain reaction (RT-PCR) was used to detect and confirm the polerovirus i.e. CYDV-rhopalosiphum padi virus (RPV), and unassigned viruses (SGV, RMV) in Punjab and NWFP provinces. The PCR products were inserted into a pGEM®-T easy vector, which then transformed in JM-107 cells of Escherichia coli. Recombinant plasmids were sequenced. Nucleotide and predicted amino acid sequences were aligned, analyzed and compared with other RPV isolates of the family. The nucleotide sequence data were used to make a phylogenetic tree.

 

Results: Sequencing of 600 bp of coat protein gene confirmed the presence of CYDV-RPV strain. Pakistani isolate has close phylogenetic relationship with RPV-Mexcio and RPV-Yolo (USA). They had 99.95% similarity with RPV-Pakistan. The RPV-Aus, RPV-IR, and RPV-Cal (USA) had 99.94% identities with RPV-Pakistan.

Conclusion: This work led to a conclusion that there is very low genetic diversity in RPV-Pakistan. Now it is in our future interest to clarify the identity of RPV-PK with more sequencing. The current study may help scientists to formulate appropriate management strategies against CYDV-RPV.

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Frontiers | Crop immunity against viruses: outcomes and future challenges | Plant-Microbe Interaction

Viruses cause epidemics on all major cultures of agronomic importance, representing a serious threat to global food security. As strict intracellular pathogens, they cannot be controlled chemically and prophylactic measures consist mainly in the destruction of infected plants and excessive pesticide applications to limit the population of vector organisms. A powerful alternative frequently employed in agriculture relies on the use of crop genetic resistances, approach that depends on mechanisms governing plant–virus interactions. Hence, knowledge related to the molecular bases of viral infections and crop resistances is key to face viral attacks in fields. Over the past 80 years, great advances have been made on our understanding of plant immunity against viruses. Although most of the known natural resistance genes have long been dominant R genes (encoding NBS-LRR proteins), a vast number of crop recessive resistance genes were cloned in the last decade, emphasizing another evolutive strategy to block viruses. In addition, the discovery of RNA interference pathways highlighted a very efficient antiviral system targeting the infectious agent at the nucleic acid level. Insidiously, plant viruses evolve and often acquire the ability to overcome the resistances employed by breeders. The development of efficient and durable resistances able to withstand the extreme genetic plasticity of viruses therefore represents a major challenge for the coming years. This review aims at describing some of the most devastating diseases caused by viruses on crops and summarizes current knowledge about plant–virus interactions, focusing on resistance mechanisms that prevent or limit viral infection in plants. In addition, I will discuss the current outcomes of the actions employed to control viral diseases in fields and the future investigations that need to be undertaken to develop sustainable broad-spectrum crop resistances against viruses.

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