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Rhizoctonia cerealis causes sharp eyespot in cereals and the pathogen survives as mycelia or sclerotia in soil. Real-time Polymerase Chain Reaction (qPCR) assays based on TaqMan chemistry are highly suitable for use on DNA extracted from soil. We report here the first qPCR assay for R. cerealis using TaqMan primers and a probe based on a unique Sequence Characterised Amplified Region (SCAR). The assay is highly specific and did not amplify DNA from a range of other binucleate Rhizoctonia species or isolates of anastomosis groups of Rhizoctonia solani. The high sensitivity of the assay was demonstrated in soils using a bulk DNA extraction method where 200 μg sclerotia in 50 g of soil were detected. DNA of the pathogen could also be amplified from asymptomatic wheat plants. Using the assay on soil samples from fields under different crop rotations, R. cerealis was most frequently detected in soils where wheat was grown or soil under pasture. It was detected least frequently in fields where potatoes were grown. This study demonstrates that assays derived from SCAR sequences can produce specific and sensitive qPCR assays. [ABSTRACT FROM AUTHOR]

Pest and pathogens pose a major threat to food security and the natural environment, and these threats are moving around the globe. Trade, travel and transport have major roles to play in this and thus to improve plant biosecurity, we need enhanced phytosanitary inspection systems. In order to achieve this, there is a role for the more effective use of diagnostic technology, such as field-based testing or the use of next generation sequencing technology. In this review we examine the opportunities and challenges posed by using new technology within a plant biosecurity context, but in contrast to previous reviews, here we focus on practical challenges associated with deployment and routine use, rather than specific technical issues. These key challenges include the need to accelerate the development and deployment of new technologies into the field, the accelerated discovery of new pathogens and the need for new risk assessment approaches, and improvements to our understanding of how best to deploy and use new diagnostic tools for maximum impact. Throughout we focus on how interdisciplinary approaches are important to help us improve our understanding and achieve our goals. [ABSTRACT FROM AUTHOR]

The complete nucleotide sequences of RNA 1 and RNA 2 of the nepovirus potato black ringspot virus (PBRSV) from two different isolates were determined, as well as partial sequences from two additional isolates. RNA1 is 7,579-7,598 nucleotides long and contains one single open reading frame (ORF), which is translated into a large polyprotein with 2,325 amino acids and a molecular weight of 257 kDa. The complete sequence of RNA2 ranges from 3857 to 3918 nt between the different isolates. It encodes a polyprotein of 1079-1082 amino acids with a molecular weight of 120 kDa. Sequence comparison using the Pro-Pol region and CP showed that all four isolates formed two distinct groups, corresponding to potato and arracacha, that were closely related to each other and also to tobacco ringspot virus (TRSV). Comparing our data to those obtained with other nepoviruses, our results confirm that PBRSV belongs to a distinct species and is a member of subgroup A in the genus Nepovirus based on its RNA2 size, genome organization, and nucleotide sequence. [ABSTRACT FROM AUTHOR]

This study reports the first complete genome sequence of Piper yellow mottle virus (PYMoV, KC808712) identified in black pepper. The genome is 7,622 nucleotides long, possessing four open reading frames (ORFs). ORF1, ORF2 and ORF4 of PYMoV are reported as hypothetical proteins of unknown function with a predicted molecular mass of 15.7, 17.1 and 17.9 kDa, respectively. ORF3 of PYMoV encodes a polyprotein of 218.6 kDa and consists of a viral movement protein (MP), trimeric dUTPase, zinc finger, retropepsin, RT-LTR, and RNAse H. Detailed PYMoV genome analysis confirmed that it is a member of the family Caulimoviridae, genus Badnavirus. Fragments of two additional novel sequences resembling those found in members of the family Caulimoviridae were also identified in the black pepper sample, and the viruses from which they were derived were tentatively named Piper DNA virus 1 and 2. [ABSTRACT FROM AUTHOR]

Guignardia citricarpa Kiely (anamorph Phyllosticta citricarpa Van der Aa), the causal agent of citrus black spot disease, is subject to phytosanitary restrictions in the EU and USA, such that consignments of citrus are rejected at import if citrus black spot is identified on inspection. Due to the variability of black spot symptoms, positive identification solely on the basis of visual inspection is difficult, especially when lesions lack pycnidia (fruiting bodies of the anamorph Phyllosticta citricarpa). As an aid to visual inspection of symptoms, we have developed a method for detection of G. citricarpa using loop-mediated isothermal amplification (LAMP) which can be used to confirm the presence of G. citricarpa in black spot lesions, including those lacking pycnidia. The LAMP assay can be used to test crude extracts prepared directly from lesions on fruit, and the entire test can be completed in less than 40 min, making it faster than previously described PCR-based methods for detection of G. citricarpa. The method is sufficiently simple to allow deployment of the test in the field, for example in the course of import inspections. Recent years have seen the description of a number of newly recognised species in the genus Phyllosticta that are associated with citrus. As new species emerge, and the taxonomy of the genus is resolved, it will be important to periodically re-evaluate the performance of DNA-based methods for detection of G. citricarpa, including the LAMP assay described here, such that the accuracy of diagnosis can be assured. [ABSTRACT FROM AUTHOR]

The complete genome sequences of RNA1 and RNA2 of the oca strain of the potato virus arracacha virus B were determined using next-generation sequencing. The RNA1 molecule is predicted to encode a 259-kDa polyprotein with homology to proteins of the cheraviruses apple latent spherical virus (ALSV) and cherry rasp leaf virus (CRLV). The RNA2 molecule is predicted to encode a 102-kDa polyprotein which also has homology to the corresponding protein of ALSV and, to a lesser degree, CRLV (30 % for RNA1, 24 % for RNA2). Detailed analysis of the genome sequence confirms that AVB is a distinct member of the genus Cheravirus. [ABSTRACT FROM AUTHOR]

The complete genome sequence for an isolate of the Ugandan and Tanzanian strain types of Cassava brown streak virus have been determined using the novel approach of non-directed next generation sequencing. Comparison of the genome sequences revealed that CBSV is highly heterogeneous at the isolate level as well as the strain level. The isolate of the Ugandan strain was found to have a genome 9,070 nucleotides long coding for a polypeptide with 2,902 amino acid residues. The isolate of the Tanzanian strain was 9,008 nucleotides long and coded for a polypeptide with 2,916 amino acid residues. Nucleotide identity between the isolates across the genome was 76%, with protein encoding regions 57–77% and individual proteins had 65–91% amino acid similarity. In addition between the two strains four protein products (PIPO, CI, NIa-Vpg and coat protein) varied in size and an unusual HAM1-like protein, whilst of identical nucleotide length, was found to have the lowest homology. The implication of diversity of CBSV is discussed in the context of speciation, evolution, development of diagnostics, and breeding for resistance. [ABSTRACT FROM AUTHOR]

Potato virus Y (PVY) strain groups are based on host response and resistance gene interactions. The strain groups PVYO, PVYC and PVYN are well established for the isolates infecting potato in the field. A switch in the emphasis from host response to nucleotide sequence differences in the virus genomes, detection of isolates recombining sequences of different strains, and the need to recognize isolates that cause necrotic symptoms in potato tubers have led to the assignment of new acronyms, especially to isolates of the PVYN strain group. This discussion paper proposes that any newly found isolates should be described within the context of the original strain groups based on the original methods of distinguishing strains (i.e., tobacco and potato assays involving use of ‘differential’ potato cultivars). Additionally, sequence characterization of the complete genomes of isolates is highly recommended. However, it is acceptable to amend the names of PVY isolates with additional, specific codes to show that the isolate differs at the molecular, serological or phenotypic level from the typical strains within a strain group. The new isolates should preferably not be named using geographical, cultivar, or place-association designations. Since many new variants of PVY are being discovered, any new static classification system will be meaningless for the time being. A more systematic investigation and characterization of PVY from potato at the biological and molecular levels should eventually result in a biologically meaningful genetic strain concept. [ABSTRACT FROM AUTHOR]

Two types of RNA-5-containing beet necrotic yellow vein virus (BNYVV) have been detected in the UK at different sites in Norfolk. On the basis of nucleotide (nt) sequence comparisons, one virus source (UK-MH) was clearly identified as P type BNYVV, a virus type that had previously only been detected in two widely separated parts of the world, France and Kazakhstan. The other virus source (UK-FF) has a complex genome composition. The analysed portions of its RNAs 2 and 4 are closely related to the corresponding portions in the RNAs of the East Asian A type isolate S, whereas those of its RNAs 1 and 3 resemble P type RNA 1 from Kazakhstan and European A type RNA 3, respectively. Interestingly, the P25 encoded on its RNA 3 has an unique TYHG tetrad in the highly variable amino acid positions 67–70. RNA 5 of the UK-FF BNYVV source shares properties with P type RNA 5, but also with East Asian types of RNA 5. The possible origin and epidemiology of BNYVV types is discussed. [ABSTRACT FROM AUTHOR]

Summary. The detection of Beet necrotic yellow vein virus (BNYVV) instored sugar beets by means of monoclonal antibodies or antibody singlechain fragments (scFv) often poses problems, because the immunodominantC-terminal epitope of the viral coat protein is readily lost due toproteolysis. Clones which produce scFv specific for protease-stableBNYVV epitopes were selected from two naive phage display libraries.Fusion proteins of the scFv with a human IgG kappa chain (expressed fromthe newly designed vector pCL) or with alkaline phosphatase,respectively, allow the ELISA detection of BNYVV even in stored sugarbeets with a sensitivity which was comparable or often higher than thatachieved with polyclonal antibodies. [ABSTRACT FROM AUTHOR]

The 9573-nucleotide genome of a potyvirus was sequenced from a Coriandrum sativum plant from India with viral symptoms. On analysis, this virus was shown to have greater than 85 % nucleotide sequence identity to vanilla distortion mosaic virus (VDMV). Analysis of the putative coat protein sequence confirmed that this virus was in fact VDMV, with greater than 91 % amino acid sequence identity. The genome appears to encode a 3083-amino-acid polyprotein potentially cleaved into the 10 mature proteins expected in potyviruses. Phylogenetic analysis confirmed that VDMV is a distinct but ungrouped member of the genus Potyvirus. [ABSTRACT FROM AUTHOR]