Sugarbeet Pathology
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Mutations in the CYP51 gene reduce DMI sensitivity in Parastagonospora nodorum populations in Europe and China - Pereira - 2016 - Pest Management Science - 

Mutations in the CYP51 gene reduce DMI sensitivity in Parastagonospora nodorum populations in Europe and China - Pereira - 2016 - Pest Management Science -  | Sugarbeet Pathology | Scoop.it
Sterol demethylation inhibitors or DMIs have been widely used to manage agronomically important fungal diseases in wheat, but reports of DMI-resistant pathogens continue to mount. Parastagonospora nodorum shows a wide range of sensitivity to DMIs, but until now no molecular mechanisms were identified to explain these differences. The aim of this study was to correlate the DMI sensitivity of a global collection of P. nodorum isolates with mutations in the CYP51 gene that encodes the target of DMI fungicides.
RESULTS

Two non-synonymous mutations connected to DMI resistance in other plant pathogenic fungi were detected for the first time in the CYP51 gene of P. nodorum. The two mutations occurred at amino acid position 144, which is homologous to position 137 in other pathogens. The Y144F mutation was detected in China, Denmark, Sweden and Switzerland while the Y144H mutation was found in China and Switzerland. Both mutations were correlated with significantly reduced susceptibility to the DMI fungicide propiconazole.
CONCLUSION

CYP51 mutations conferred reduced sensitivity against DMIs in field populations of P. nodorum originating from China, Denmark, Sweden and Switzerland.
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Development and evaluation of a reverse transcription loop-mediated isothermal amplification assay for detection of beet necrotic yellow vein virus - Almasi & Almasi, Archive of Virology 2016

Development and evaluation of a reverse transcription loop-mediated isothermal amplification assay for detection of beet necrotic yellow vein virus - Almasi & Almasi, Archive of Virology 2016 | Sugarbeet Pathology | Scoop.it

Sugar beet can be infected by many different viruses that can reduce yield; beet necrotic yellow vein virus (BNYVV) is one of the most economically important viruses of this crop plant. This report describes a new reverse transcription loop-mediated isothermal amplification (RT-LAMP) assay for identification of BNYVV. In addition, a novel immunocapture (IC) RT-LAMP assay for rapid and easy detection (without RNA extraction) of BNYVV was developed here and compared with DAS-ELISA and RT-LAMP assays. Our results show that the IC-RT-LAMP assay is a highly reliable alternative assay for identification of BNYVV.

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Antifungal activity of the ribosome-inactivating protein BE27 from sugar beet against Penicillium digitatum - Citores - Molecular Plant Pathology

Antifungal activity of the ribosome-inactivating protein BE27 from sugar beet against Penicillium digitatum - Citores - Molecular Plant Pathology | Sugarbeet Pathology | Scoop.it

The ribosome-inactivating protein BE27, from sugar beet (Beta vulgaris L.) leaves, is an apoplastic protein induced by signaling compounds such as hydrogen peroxide and salicylic acid that has been reported to be involved in the defense against viruses. Here, we report that BE27 displays, at a concentration much lower than that present in the apoplast, antifungal activity against the green moldPenicillium digitatum, a necrotrophic fungus that colonize the wounds and grow in the inter- and intra-cellular spaces of the tissues of several edible plants. BE27 is able to enter into the cytosol and kill fungal cells thus arresting the growth of the fungus. The mechanism of action seems to lie with its rRNA N-glycosylase activity on the Sarcin Ricin Loop of the major ribosomal RNA that inactivates irreversibly the fungal ribosomes thus inhibiting protein synthesis. We compare the C-terminus of the BE27 structure with antifungal plant defensins and hypothesized that a structural motif composed of an α-helix and a β-hairpin similar to the γ-core motif of defensins might contribute to the specific interaction with the fungal plasma membranes allowing the protein to enter into the cell.

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Reliable In Silico Identification of Sequence Polymorphisms and Their Application for Extending the Genetic Map of Sugar Beet (Beta vulgaris)

Reliable In Silico Identification of Sequence Polymorphisms and Their Application for Extending the Genetic Map of Sugar Beet (Beta vulgaris) | Sugarbeet Pathology | Scoop.it
Molecular markers are a highly valuable tool for creating genetic maps. Like in many other crops, sugar beet (Beta vulgaris L.) breeding is increasingly supported by the application of such genetic markers. Single nucleotide polymorphism (SNP) based markers have a high potential for automated analysis and high-throughput genotyping. We developed a bioinformatics workflow that uses Sanger and 2nd-generation sequence data for detection, evaluation and verification of new transcript-associated SNPs from sugar beet. RNAseq data from one parent of an established mapping population were produced by 454-FLX sequencing and compared to Sanger ESTs derived from the other parent. The workflow established for SNP detection considers the quality values of both types of reads, provides polymorphic alignments as well as selection criteria for reliable SNP detection and allows painless generation of new genetic markers within genes. We obtained a total of 14,323 genic SNPs and InDels. According to empirically optimised settings for the quality parameters, we classified these SNPs into four usability categories. Validation of a subset of the in silico detected SNPs by genotyping the mapping population indicated a high success rate of the SNP detection. Finally, a total of 307 new markers were integrated with existing data into a new genetic map of sugar beet which offers improved resolution and the integration of terminal markers.
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Coupling spore traps and quantitative PCR assays for detection of the downy mildew pathogens of spinach (Peronospora effusa) and beet (Peronospora schachtii)

Coupling spore traps and quantitative PCR assays for detection of the downy mildew pathogens of spinach (Peronospora effusa) and beet (Peronospora schachtii) | Sugarbeet Pathology | Scoop.it

Downy mildew of spinach (Spinacia oleracea L.), caused byPeronospora effusa, is a production constraint worldwide, including in California where the majority of United States spinach is grown. The aim of this study was to develop a real-time quantitative PCR (qPCR) assay for detection of airborne inoculum of P. effusa in California. Among oomycete ribosomal DNA (rDNA) sequences examined for assay development, the highest nucleotide sequence identity was observed between rDNA sequences of P. effusa and Peronospora schachtii, the cause of downy mildew on sugar beet and Swiss chard in the leaf beet group (Beta vulgaris L. subsp. vulgaris). Single nucleotide polymorphisms (SNPs) were detected between P. effusa and P. schachtii in the 18S rDNA regions for design of P. effusa- and P. schachtii-specific TaqMan probes and reverse primers. An allele-specific probe and primer amplification method was applied to determine the frequency of both P. effusa and P. schachtii rDNA target sequences in pooled DNA samples, enabling quantification of rDNA ofP. effusa from impaction spore trap samples collected from spinach production fields. The rDNA copy numbers of P. effusa were on average ~3400-fold higher from trap samples collected near an infected field as compared to those levels recorded at a site without a nearby spinach field. In combination with disease-conducive weather forecasting, application of the assays may be helpful to time fungicide applications for disease management.

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Description of Fusarium secorum - a novel pathogen of sugarbeet

Description of Fusarium secorum - a novel pathogen of sugarbeet | Sugarbeet Pathology | Scoop.it

This study characterized a novel sugar beet (Beta vulgaris L.) pathogen from the Red River Valley in north central USA, which was formally named Fusarium secorum. Molecular phylogenetic analyses of three loci (translation elongation factor1α, calmodulin, mitochondrial small subunit) and phenotypic data strongly supported the inclusion of F. secorum in the Fusarium fujikuroi species complex (FFSC). Phylogenetic analyses identified F. secorum as a sister taxon of F. acutatum and a member of the African subclade of the FFSC. Fusarium secorum produced circinate hyphae sometimes bearing microconidia and abundant corkscrew-shaped hyphae in culture. To assess mycotoxin production potential, 45 typical secondary metabolites were tested in F. secorum rice cultures, but only beauvericin was produced in detectable amounts by each isolate. Results of pathogenicity experiments revealed that F. secorum isolates are able to induce half- and full-leaf yellowing foliar symptoms and vascular necrosis in roots and petioles of sugar beet. Inoculation with F. acutatum did not result in any disease symptoms. The sugar beet disease caused by F. secorum is named Fusarium yellowing decline. Since Fusarium yellowing decline incidence has been increasing in the Red River Valley, disease management options are discussed.

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First Report of QOI-insensitive Powdery Mildew (Erysiphe polygoni) on Sugar Beet in the United States

First Report of QOI-insensitive Powdery Mildew (Erysiphe polygoni) on Sugar Beet in the United States | Sugarbeet Pathology | Scoop.it

The $2.1 billion United States sugar beet (Beta vulgaris L.) industry is the primary provider of domestic sucrose. Sugar beet powdery mildew is caused by Erysiphe polygoni DC and occurs principally in sugar beet growing regions in western United States. In these regions, the quinone outside inhibitor (QOI) fungicides pyraclostrobin (Headline, BASF, NC) and trifloxystrobin (Gem, Bayer Crop Science, NC) have been important tools to manage powdery mildew since registration in 2002 and 2005, respectively. However, researchers in Idaho reported poor disease management despite QOI application starting in 2011. In 2013, a research plot near Parma, ID containing natural powdery mildew infection received treatments of pyraclostrobin, trifloxystrobin, or was untreated (control). Since there was no significant reduction in disease levels between QOI-treated blocks and untreated control blocks, experiments were conducted to clone a partial fragment of theE. polygoni cytochrome b (cytb) gene to gain insight into the molecular basis of QOI resistance in this pathosystem. The primers MDB-920 (5’-CACATCGGAAGAGGTTTATA-3’) and MDB-922 (5’-GGTATAGATCTTAATATAGCATAG-3’) were designed based on consensus sequences of several fungal cytb genes obtained from GenBank (data not presented) and used to amplify a 575-bp fragment of the E. polygoni cytb gene using DNA isolated from 12 infected leaf samples collected in September 2013 from the Parma research plot. Each sample consisted of three leaves harvested from three plants (one leaf per plant) in an experimental block. All DNA extraction, PCR, and sequencing procedures were as described previously (1). PCR products derived from six QOI-treated samples and six untreated samples were sequenced directly. Without exception, all QOI-treated samples harbored a point mutation at nucleotide position 143 that encoded a G143A mutation compared with cytb sequence from untreated samples. The two identified cytb haplotypes have been deposited in GenBank under accession numbers KF925325 and KF925326. This is the first report of QOI resistance and the associatedcytb G143A mutation in E. polygoni. The G143A mutation has been reported in most QOI-resistant pathogens to date (2). When the G143A mutation dominates in a pathogen population, there is a consistent association with a loss of disease management despite QOI application (3). Careful monitoring and judicious use of QOI fungicides will be necessary to ensure QOI fungicides remain efficacious for sugar beet powdery mildew management in the U. S.

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The genome of the recently domesticated crop plant sugar beet (Beta vulgaris) - Nature

The genome of the recently domesticated crop plant sugar beet (Beta vulgaris) - Nature | Sugarbeet Pathology | Scoop.it

Sugar beet (Beta vulgaris ssp. vulgaris) is an important crop of temperate climates which provides nearly 30% of the world’s annual sugar production and is a source for bioethanol and animal feed. The species belongs to the order of Caryophylalles, is diploid with 2n = 18 chromosomes, has an estimated genome size of 714–758 megabases1 and shares an ancient genome triplication with other eudicot plants2. Leafy beets have been cultivated since Roman times, but sugar beet is one of the most recently domesticated crops. It arose in the late eighteenth century when lines accumulating sugar in the storage root were selected from crosses made with chard and fodder beet3. Here we present a reference genome sequence for sugar beet as the first non-rosid, non-asterid eudicot genome, advancing comparative genomics and phylogenetic reconstructions. The genome sequence comprises 567 megabases, of which 85% could be assigned to chromosomes. The assembly covers a large proportion of the repetitive sequence content that was estimated4 to be 63%. We predicted 27,421 protein-coding genes supported by transcript data and annotated them on the basis of sequence homology. Phylogenetic analyses provided evidence for the separation of Caryophyllales before the split of asterids and rosids, and revealed lineage-specific gene family expansions and losses. We sequenced spinach (Spinacia oleracea), another Caryophyllales species, and validated features that separate this clade from rosids and asterids. Intraspecific genomic variation was analysed based on the genome sequences of sea beet (Beta vulgaris ssp. maritima; progenitor of all beet crops) and four additional sugar beet accessions. We identified seven million variant positions in the reference genome, and also large regions of low variability, indicating artificial selection. The sugar beet genome sequence enables the identification of genes affecting agronomically relevant traits, supports molecular breeding and maximizes the plant’s potential in energy biotechnology.

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Protozoa Drive the Dynamics of Culturable Biocontrol Bacterial Communities. Müller et al., PLoS ONE

Protozoa Drive the Dynamics of Culturable Biocontrol Bacterial Communities.  Müller et al., PLoS ONE | Sugarbeet Pathology | Scoop.it

Some soil bacteria protect plants against soil-borne diseases by producing toxic secondary metabolites. Such beneficial biocontrol bacteria can be used in agricultural systems as alternative to agrochemicals. The broad spectrum toxins responsible for plant protection also inhibit predation by protozoa and nematodes, the main consumers of bacteria in soil. Therefore, predation pressure may favour biocontrol bacteria and contribute to plant health. We analyzed the effect of Acanthamoeba castellanii on semi-natural soil bacterial communities in a microcosm experiment. We determined the frequency of culturable bacteria carrying genes responsible for the production of the antifungal compounds 2,4-diacetylphloroglucinol (DAPG), pyrrolnitrin (PRN) and hydrogen cyanide (HCN) in presence and absence of A. castellanii. We then measured if amoebae affected soil suppressiveness in a bioassay with sugar beet seedlings confronted to the fungal pathogen Rhizoctonia solani. Amoebae increased the frequency of both DAPG and HCN positive bacteria in later plant growth phases (2 and 3 weeks), as well as the average number of biocontrol genes per bacterium. The abundance of DAPG positive bacteria correlated with disease suppression, suggesting that their promotion by amoebae may enhance soil health. However, the net effect of amoebae on soil suppressiveness was neutral to slightly negative, possibly because amoebae slow down the establishment of biocontrol bacteria on the recently emerged seedlings used in the assay. The results indicate that microfaunal predators foster biocontrol bacterial communities. Understanding interactions between biocontrol bacteria and their predators may thus help developing environmentally friendly management practices of agricultural systems.

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'Mystery' condition hits sugar crops

'Mystery' condition hits sugar crops | Sugarbeet Pathology | Scoop.it
Sugar beet farmers are counting the cost of a "mystery" condition resulting in more than 50% of some crops failing.
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Systemic resistance induced by Bacillus lipopeptides in Beta vulgaris reduces infection by the rhizomania disease vector Polymyxa betae - Desoignies - 2012 - Molecular Plant Pathology

Systemic resistance induced by Bacillus lipopeptides in Beta vulgaris reduces infection by the rhizomania disease vector Polymyxa betae - Desoignies - 2012 - Molecular Plant Pathology | Sugarbeet Pathology | Scoop.it

The control of rhizomania, one of the most important diseases of sugar beet caused by the Beet necrotic yellow vein virus, remains limited to varietal resistance. In this study, we investigated the putative action of Bacillus amylolequifaciens lipopeptides in achieving rhizomania biocontrol through the control of the virus vector Polymyxa betae. Some lipopeptides that are produced by bacteria, especially by plant growth-promoting rhizobacteria, have been found to induce systemic resistance in plants. We tested the impact of the elicitation of systemic resistance in sugar beet through lipopeptides on infection by P. betae. Lipopeptides were shown to effectively induce systemic resistance in both the roots and leaves of sugar beet, resulting in a significant reduction in P. betae infection. This article provides the first evidence that induced systemic resistance can reduce infection of sugar beet by P. betae.

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Effect of sugar beet genotype on the Beet necrotic yellow vein virus P25 pathogenicity factor and evidence for a fitness penalty in resistance-breaking strains - Bornemann - 2013 - Molecular Plant ...

Effect of sugar beet genotype on the Beet necrotic yellow vein virus P25 pathogenicity factor and evidence for a fitness penalty in resistance-breaking strains - Bornemann - 2013 - Molecular Plant ... | Sugarbeet Pathology | Scoop.it

Beet necrotic yellow vein virus (BNYVV), vectored by Polymyxa betae, causes rhizomania in sugar beet. For disease control, the cultivation of hybrids carrying Rz1 resistance is crucial, but is compromised by resistance-breaking (RB) strains with specific mutations in the P25 protein at amino acids 67–70 (tetrad). To obtain evidence for P25 variability from soil-borne populations, where the virus persists for decades, populations with wild-type (WT) and RB properties were analysed by P25 deep sequencing. The level of P25 variation in the populations analysed did not correlate with RB properties. Remarkably, one WT population contained P25 with RB mutations at a frequency of 11%. To demonstrate selection by Rz1 and the influence of RB mutations on relative fitness, competition experiments between strains were performed. Following a mixture of strains with four RNAs, a shift in tetrad variants was observed, suggesting that strains did not mix or transreplicate. The plant genotype exerted a clear influence on the frequency of RB tetrads. In Rz1 plants, the RB variants outcompeted the WT variants, and mostly vice versa in susceptible plants, demonstrating a relative fitness penalty of RB mutations. The strong genotype effect supports the hypothesized Rz1 RB strain selection with four RNAs, suggesting that a certain tetrad needs to become dominant in a population to influence its properties. Tetrad selection was not observed when an RB strain, with an additional P26 protein encoded by a fifth RNA, competed with a WT strain, supporting its role as a second BNYVV pathogenicity factor and suggesting the reassortment of both types.

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Non-invasive Presymptomatic Detection of Cercospora beticola Infection and Identification of Early Metabolic Responses in Sugar Beet

Non-invasive Presymptomatic Detection of Cercospora beticola Infection and Identification of Early Metabolic Responses in Sugar Beet | Sugarbeet Pathology | Scoop.it

Cercospora beticola is an economically significant fungal pathogen of sugar beet, and is the causative pathogen of Cercospora leaf spot. Selected host genotypes with contrasting degree of susceptibility to the disease have been exploited to characterize the patterns of metabolite responses to fungal infection, and to devise a pre-symptomatic, non-invasive method of detecting the presence of the pathogen. Sugar beet genotypes were analyzed for metabolite profiles and hyperspectral signatures. Correlation of data matrices from both approaches facilitated identification of candidates for metabolic markers. Hyperspectral imaging was highly predictive with a classification accuracy of 98.5-99.9% in detecting C. beticola. Metabolite analysis revealed metabolites altered by the host as part of a successful defense response: these were L-DOPA, 12-hydroxyjasmonic acid 12-O-β-D-glucoside, pantothenic acid, and 5-O-feruloylquinic acid. The accumulation of glucosylvitexin in the resistant cultivar suggests it acts as a constitutively produced protectant. The study establishes a proof-of-concept for an unbiased, presymptomatic and non-invasive detection system for the presence of C. beticola. The test needs to be validated with a larger set of genotypes, to be scalable to the level of a crop improvement program, aiming to speed up the selection for resistant cultivars of sugar beet. Untargeted metabolic profiling is a valuable tool to identify metabolites which correlate with hyperspectral data.

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Development of a DNA microarray based assay for the detection of sugar beet root rot pathogens — Phytopathology

Development of a DNA microarray based assay for the detection of sugar beet root rot pathogens — Phytopathology | Sugarbeet Pathology | Scoop.it

Sugar beet root rot diseases that occur during the cropping season or in storage are accompanied by high yield losses and a severe reduction of processing quality. The vast diversity of microorganism species involved in rot development requires molecular tools allowing simultaneous identification of many different targets. Therefore, a new microarray technology (ArrayTube) was applied in this study to improve diagnosis of sugar beet root rot diseases. Based on three marker genes (internal transcribed spacer, translation elongation factor 1 alpha and 16S ribosomal DNA), 42 well performing probes enabled the identification of prevalent field pathogens (e.g. Aphanomyces cochlioides), storage pathogens (e.g. Botrytis cinerea) and ubiquitous spoilage fungi (e.g. Penicillium expansum). All probes were proven for specificity with pure cultures from 73 microorganism species as well as for in planta detection of their target species using inoculated sugar beet tissue. Microarray based identification of root rot pathogens in diseased field beets was successfully confirmed by classical detection methods. The high discriminatory potential was proven by Fusarium species differentiation based on a single nucleotide polymorphism. The results demonstrate that the ArrayTube constitute an innovative tool allowing a rapid and reliable detection of plant pathogens particularly when multiple microorganism species are present.

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Magnetic resonance imaging of sugar beet taproots in soil reveals growth reduction and morphological changes during foliar Cercospora beticola infestation

Magnetic resonance imaging of sugar beet taproots in soil reveals growth reduction and morphological changes during foliar Cercospora beticola infestation | Sugarbeet Pathology | Scoop.it

Cercospora leaf spot (CLS) infection can cause severe yield loss in sugar beet. Introduction of Cercospora-resistant varieties in breeding programmes is important for plant protection to reduce both fungicide applications and the risk of the development of fungal resistance. However, in vivo monitoring of the sugar-containing taproots at early stages of foliar symptoms and the characterization of the temporal development of disease progression has proven difficult. Non-invasive magnetic resonance imaging (MRI) measurements were conducted to quantify taproot development of genotypes with high (HS) and low (LS) levels of susceptibility after foliar Cercospora inoculation. Fourteen days post-inoculation (dpi) the ratio of infected leaf area was still low (~7%) in both the HS and LS genotypes. However, during this period, the volumetric growth of the taproot had already started to decrease. Additionally, inoculated plants showed a reduction of the increase in width of inner cambial rings while the width of outer rings increased slightly compared with non-inoculated plants. This response partly compensated for the reduced development of inner rings that had a vascular connection withCercospora-inoculated leaves. Hence, alterations in taproot anatomical features such as volume and cambial ring development can be non-invasively detected already at 14 dpi, providing information on the early impact of the infection on whole-plant performance. All these findings show that MRI is a suitable tool to identify promising candidate parent lines with improved resistance to Cercospora, for example with comparatively lower taproot growth reduction at early stages of canopy infection, for future introduction into breeing programmes.

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The Scientist: Opinion: The Planet Needs More Plant Scientists (2014)

The Scientist: Opinion: The Planet Needs More Plant Scientists (2014) | Sugarbeet Pathology | Scoop.it

Academia is not producing sufficient PhDs in the plant sciences to solve the crop production challenges facing a rapidly growing population.


Via Kamoun Lab @ TSL
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Peter Buckland's curator insight, October 2, 2014 6:34 AM

Yet more evidence of the decline in plant sciences

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Spatial genetic structure in Beta vulgaris subsp. maritima and Beta macrocarpa reveals the effect of contrasting mating system, influence of marine currents, and footprints of postglacial recoloniz...

Spatial genetic structure in Beta vulgaris subsp. maritima and Beta macrocarpa reveals the effect of contrasting mating system, influence of marine currents, and footprints of postglacial recoloniz... | Sugarbeet Pathology | Scoop.it

Understanding the factors that contribute to population genetic divergence across a species' range is a long-standing goal in evolutionary biology and ecological genetics. We examined the relative importance of historical and ecological features in shaping the present-day spatial patterns of genetic structure in two related plant species, Beta vulgaris subsp. maritima and Beta macrocarpa. Using nuclear and mitochondrial markers, we surveyed 93 populations from Brittany (France) to Morocco – the southern limit of their species' range distribution. Whereas B. macrocarpa showed a genotypic structure and a high level of genetic differentiation indicative of selfing, the population genetic structure of B. vulgaris subsp. maritima was consistent with an outcrossing mating system. We further showed (1) a strong geographic clustering in coastal B. vulgaris subsp. maritima populations that highlighted the influence of marine currents in shaping different lineages and (2) a peculiar genetic structure of inland B. vulgaris subsp. maritima populations that could indicate the admixture of distinct evolutionary lineages and recent expansions associated with anthropogenic disturbances. Spatial patterns of nuclear diversity and differentiation also supported a stepwise recolonization of Europe from Atlantic-Mediterranean refugia after the last glacial period, with leading-edge expansions. However, cytoplasmic diversity was not impacted by postglacial recolonization: stochastic long-distance seed dispersal mediated by major oceanic currents may mitigate the common patterns of reduced cytoplasmic diversity observed for edge populations. Overall, the patterns we documented here challenge the general view of reduced genetic diversity at the edge of a species' range distribution and provide clues for understanding how life-history and major geographic features interact to shape the distribution of genetic diversity.

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Infection of Beet necrotic yellow vein virus with RNA4-encoded P31 specifically up-regulates PR-10 in Nicotiana benthamiana - Wu et al - Virology Journal

Background

Beet necrotic yellow vein virus (BNYVV) is the infectious agent of sugar beet rhizomania, which consists of four or five plus-sense RNAs. RNA4 of BNYVV is not essential for virus propagation in Nicotiana benthamiana but has a major effect on symptom expression. Early reports showed that RNA4-encoded P31 was associated with severe symptoms, such as curling and dwarfing, in N. benthamiana.

Results

We discovered that the pathogenesis-related protein 10 (PR-10) gene can be up-regulated in BNYVV-infected N. benthamiana in the presence of RNA4 and that it had a close link with symptom development. Our frame-shift, deletion and substitution analysis showed that only the entire P31 could induce PR-10 up-regulation during BNYVV infection and that all the tryptophans and six cysteines (C174, C183, C186, C190, C197 and C199) in the cysteine-rich P31 had significant effects on PR-10 expression. However, P31 could not interact directly with PR-10 in yeast.

Conclusions

Our data demonstrated that only integrated P31 specifically induced PR-10 transcription, which coincided closely with the appearance of severe symptoms in BNYVV-infected N. benthamiana, although they could not interact directly with each other in yeast.

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Multilocus analysis using putative fungal effectors to describe a population of Fusarium oxysporum from sugar beet - Covey et al Phytopathol

Multilocus analysis using putative fungal effectors to describe a population of Fusarium oxysporum from sugar beet - Covey et al Phytopathol | Sugarbeet Pathology | Scoop.it

Sugar beet (Beta vulgaris L.) Fusarium yellows is caused by Fusarium oxysporum Schlechtend.:Fr. f. sp. betae (D. Stewart) and leads to significant reductions in root yield, sucrose percentage, juice purity, and storability. F. oxysporum f. sp. betae can be highly variable and many F. oxysporum isolated from symptomatic sugar beet are non-pathogenic. Identifying pathogenicity factors and their diversity in the F. oxysporum f. sp. betae population could further understanding of how this pathogen causes disease and provide molecular markers to rapidly identify pathogenic isolates. This study used several previously described fungal pathogenicity genes (Fmk1, Fow1, Pda1, PelA, PelD, Pep1, Prt1, Rho1, Sge1, Six1, Six6, Snf1, and Ste12) as genetic markers, in a population of 26 pathogenic and non-pathogenic isolates of F. oxysporum originally isolated from symptomatic sugar beet. Of the genes investigated, 6 were present in all F. oxysporum isolates from sugar beet (Fmk1, Fow1, PelA, Rho1, Snf1, and Ste12), and 7 were found to be dispersed within the population (Pda1, PelD, Pep1, Prt1, Sge1, Six1, and Six6). Of these, Fmk1, Fow1, PelA, Rho1, Sge1, Snf1, and Ste12 were significant in describing clade designations and PelD, and Prt1 were significant for describing pathogenicity in F. oxysporum f. sp. betae.

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First Evidence of a Binucleate Rhizoctonia as the Causal Agent of Dry Rot Canker of Sugar Beet in Nebraska. Plant Disease - Harveson and Bolton

First Evidence of a Binucleate Rhizoctonia as the Causal Agent of Dry Rot Canker of Sugar Beet in Nebraska. Plant Disease - Harveson and Bolton | Sugarbeet Pathology | Scoop.it

Sugar beet (Beta vulgaris L.) is the primary source of domestic sucrose in the United States. In 2011, a sugar beet field in Morrill County, NE, was noted with wilting and yellowing symptoms suggestive of Rhizoctonia root and crown rot (RRCR), an important disease of sugar beet primarily caused by Rhizoctonia solani anastomosis group 2-2 (4). While the foliar symptoms were consistent with RRCR, the symptoms on the root were not. Root symptoms consisted of localized, dry, sunken lesions covering brown spongy tissue penetrating deeply into taproots. The surface tissues of the cankers distinctively produced a series of concentric circles. These root symptoms are inconsistent with RRCR, but are suggestive of a rarely occurring disease known as dry rot canker (DRC). DRC was first identified from Utah in 1921 (1), and assumed at the time to be caused by an uncharacterized strain ofR. solani. It has since been sporadically but empirically noted from most western sugar beet growing states (4), but little is known about the pathogen or disease due to its infrequent appearances. To investigate the etiology of this disease, necrotic lesion borders were excised from diseased taproots, surface disinfested in 1% (v/v) sodium hypochlorite for 90 s, rinsed with distilled water for 90 s, and after drying on sterile tissue paper, placed on half-strength potato dextrose agar (½PDA) and incubated at 25 to 27°C. After 24 to 36 h,Rhizoctonia-like fungal growth was readily observed emerging from tissue pieces. Resulting colonies were tan to light brown. The ITS region of the rDNA was amplified from 4 isolates obtained from 4 distinct lesions and roots using the ITS1 and ITS4 primers (3) with standard PCR conditions, and sequenced (GenBank KC842197 to KC842200). The ITS regions were 100% identical between the 4 isolates and 96% (E-value = 0.0) identical to binucleate Rhizoctoniaand Ceratobasidium sp. AG-F (e.g., JF519832, FR734295, JF705217). Hyphal cells were observed to be binucleate after staining 48-h-old cultures with lactophenol blue. Therefore, these isolates were identified to be a binucleate Rhizoctonia group AG-F based on morphological and molecular characteristics. Although distinct from DRC, a similar phenomenon has been recently reported from China implicating binucleate Rhizoctonia species with seedling disease in sugar beets (2). To determine pathogenicity of DRC isolates, 1- and 2-month-old sugar beet plants grown in 10 cm pots (5 plants per pot with 4 replications per isolate) were inoculated with all 4 isolates by placing 3 mycelial plugs (8 mm diameter) taken from the leading edge of ½PDA plates onto the soil surface of each pot. PDA plugs were utilized as controls. After ~3 weeks, root lesions resembling DRC were observed and isolates were recovered and identified from diseased plants as described above. No symptoms developed on control plants. To our knowledge, this is the first formally confirmed report of DRC on sugar beets in more than 75 years from the Western Hemisphere. The original investigator suspected that the isolates he found inducing this disease were different from typical R. solani isolates based on different symptoms (1). Our results, based on different symptoms but also with distinct molecular, biological, and pathogenicity traits, validate those suspicions while also fulfilling Koch's postulates with binucleate Rhizoctonia AG-F pathogenic to sugar beet that is distinct from the more common R. solani.

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The heterothallic sugarbeet pathogen Cercospora beticola contains exon fragments of both MAT genes that are homogenized by concerted evolution - Bolton et al. Fungal Genetics and Biology

The heterothallic sugarbeet pathogen Cercospora beticola contains exon fragments of both MAT genes that are homogenized by concerted evolution - Bolton et al. Fungal Genetics and Biology | Sugarbeet Pathology | Scoop.it

Dothideomycetes is one of the most ecologically diverse and economically important classes of fungi. Sexual reproduction in this group is governed by mating type (MAT) genes at the MAT1 locus. Self-sterile (heterothallic) species contain one of two genes at MAT1 (MAT1-1-1 or MAT1-2-1) and only isolates of opposite mating type are sexually compatible. In contrast, self-fertile (homothallic) species contain bothMAT genes at MAT1. Knowledge of the reproductive capacities of plant pathogens are of particular interest because recombining populations tend to be more difficult to manage in agricultural settings. In this study, we sequenced MAT1 in the heterothallic Dothideomycete fungus Cercospora beticola to gain insight into the reproductive capabilities of this important plant pathogen. In addition to the expected MAT gene at MAT1, each isolate contained fragments of both MAT1-1-1 and MAT1-2-1 at ostensibly random loci across the genome. When MAT fragments from each locus were manually assembled, they reconstituted MAT1-1-1and MAT1-2-1 exons with high identity, suggesting a retroposition event occurred in a homothallic ancestor in which both MAT genes were fused. The genome sequences of related taxa revealed that MAT gene fragment pattern of Cercosporazeae-maydis was analogous to C. beticola. In contrast, the genome of more distantly related Mycosphaerella graminicola did not contain MAT fragments. Although fragments occurred in syntenic regions of the C. beticola and C. zeae-maydis genomes, each MAT fragment was more closely related to the intact MAT gene of the same species. Taken together, these data suggest MAT genes fragmented after divergence of M. graminicola from the remaining taxa, and concerted evolution functioned to homogenize MAT fragments and MAT genes in each species.

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Disease variation and chemical control of Ramularia leaf spot in sugar beet - Thach et al. - Crop Protection

Disease variation and chemical control of Ramularia leaf spot in sugar beet - Thach et al. - Crop Protection | Sugarbeet Pathology | Scoop.it

Data from 1999 to 2009 on Ramularia leaf spot caused by Ramularia beticola in sugar beet showed that it was a serious disease in sugar beet in 5 out of 11 seasons. The severity and significance of the disease was found to vary depending on events with precipitation, particularly in two specific weeks in July and September. Several fungicides were found to give effective control, and positive net yield responses were found in 9 out of 11 seasons. The average sugar yield response varied in individual years between 0.7 and 2.2 t ha−1. High levels of control of Ramularia leaf spot was obtained in field trials, a semi-field trial and anin vitro test using the compounds pyraclostrobin, epoxiconazole, difenoconazole and propiconazole. Dose response trials with epoxiconazole from two seasons showed both reduced efficacy and yield responses from low doses. They also proved that the optimal input of fungicides varies significantly between seasons depending on disease severity. A sensitivity test of R. beticola to different fungicides showed a normal distribution of sensitivity with no sign of resistance development to either strobilurins or triazoles. Results from a semi-field trial showed both good preventive and curative effects with 84–100% disease control from epoxiconazole, difenoconazole and pyraclostrobin. In order to optimize an IPM control strategy better forecasting systems are needed along with cultivars providing higher levels of resistance to the disease.

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Host Growth Can Cause Invasive Spread of Crops by Soilborne Pathogens - Leclerc et al. - PLoS One

Host Growth Can Cause Invasive Spread of Crops by Soilborne Pathogens - Leclerc et al. - PLoS One | Sugarbeet Pathology | Scoop.it

Invasive soilborne plant pathogens cause substantial damage to crops and natural populations, but our understanding of how to prevent their epidemics or reduce their damage is limited. A key and experimentally-tested concept in the epidemiology of soilborne plant diseases is that of a threshold spacing between hosts below which epidemics (invasive spread) can occur. We extend this paradigm by examining how plant-root growth may alter the conditions for occurrence of soilborne pathogen epidemics in plant populations. We hypothesise that host-root growth can 1) increase the probability of pathogen transmission between neighbouring plants and, consequently, 2) decrease the threshold spacing for epidemics to occur. We predict that, in systems initially below their threshold conditions, root growth can trigger soilborne pathogen epidemics through a switch from non-invasive to invasive behaviour, while in systems above threshold conditions root growth can enhance epidemic development. As an example pathosystem, we studied the fungus Rhizoctonia solani on sugar beet in field experiments. To address hypothesis 1, we recorded infections within inoculum-donor and host-recipient pairs of plants with differing spacing. We translated these observations into the individual-level concept of pathozone, a host-centred form of dispersal kernel. To test hypothesis 2 and our prediction, we used the pathozone to parameterise a stochastic model of pathogen spread in a host population, contrasting scenarios of spread with and without host growth. Our results support our hypotheses and prediction. We suggest that practitioners of agriculture and arboriculture account for root system expansion in order to reduce the risk of soilborne-disease epidemics. We discuss changes in crop design, including increasing plant spacing and using crop mixtures, for boosting crop resilience to invasion and damage by soilborne pathogens. We speculate that the disease-induced root growth observed in some pathosystems could be a pathogen strategy to increase its population through host manipulation.

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Planting sugarbeets in warm soil will increase seedling diseases | MSU Extension

Sugarbeets planted in warm, moist soils will have an increased risk of seedling diseases such as Rhizoctonia, Pythium, Aphanomyces and Fusarium.
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