Putting 'X' into Context: The Diversity of ' Phytoplasma pruni' Strains Associated with the Induction of X-Disease.

Recurrent epiphytotics of X-disease, caused by ' Phytoplasma pruni,' have inflicted significant losses on commercial cherry and peach production across North America in the last century. During this period, there have been multiple studies reporting different disease phenotypes and, more recently, identifying different strains through sequencing core genes, but the symptoms have not, to date, been linked with genotype. Therefore, in this study we collected and assessed differing disease phenotypes from multiple U.

Bacterial Endosymbionts Identified From Leafhopper (Hemiptera: Cicadellidae) Vectors of Phytoplasmas.

Insects often harbor bacterial endosymbionts that provide them with nutritional benefit or with protection against natural enemies, plant defenses, insecticides, and abiotic stresses. Certain endosymbionts may also alter acquisition and transmission of plant pathogens by insect vectors. We identified bacterial endosymbionts from four leafhopper vectors (Hemiptera: Cicadellidae) of 'Candidatus Phytoplasma' species by direct sequencing 16S rDNA and confirmed endosymbiont presence and identity by species-specific conventional PCR.

Draft Genome Sequence of a Washington Isolate of " Phytoplasma pruni".

Illumina sequencing of a Prunus avium tree with X-disease symptoms was performed to obtain a draft genome of " Phytoplasma pruni." The genome consists of 14 contigs covering 588,767 bp. This is the first metagenome to be sequenced from the current X-disease epidemic in stone fruit in the Pacific Northwest.

Improved Detection of Using a Hydrolysis Probe to Manage the Pacific Northwest Little Cherry Disease Epidemic.

(LChV-2) is a viral pathogen that is reaching epidemic levels in Washington State. This virus is insect vectored and has significant impacts on sweet cherry production. To aid growers in making informed management decisions, we sought to develop a diagnostic assay to better detect isolates of LChV-2 currently found in Washington, allowing more accurate estimations of disease occurrence.

Titer and distribution of little cherry virus 2 in Prunus avium.

Little cherry virus 2 (LChV-2) is a causal agent of little cherry disease, which produces small, misshapen fruit with poor color and taste. As LChV-2 symptoms are only present near harvest, molecular detection is essential for effective control. Therefore, we determined the titer and distribution of this virus in infected trees over time.

Optimization of a Method for the Concentration of Genetic Material in Bacterial and Fungal Communities on Fresh Apple Peel Surfaces.

Apples are the most consumed fruit in the United States and have recently been shown to exhibit some vulnerability to contamination across the supply chain. It is unclear what role a fruit microbiome analysis may serve in future food safety programs interested in understanding changes in the product and the processing environment. Ultimately, sample integrity is key if any of these approaches are to be employed; low microbial loads on apple surfaces, the inability to sample the entire surface, and inefficiency of removal may act as barriers to achieving high-quality DNA.

A bushel of viruses: Identification of seventeen novel putative viruses by RNA-seq in six apple trees.

Apple decline in Washington state has been increasing in incidence, particularly on Honeycrisp trees grown on G.935 rootstock. In this disease the trees exhibit dieback with necrosis at the graft union and in the rootstock.

A New Era for Mild Strain Cross-Protection.

Societal and environmental pressures demand high-quality and resilient cropping plants and plant-based foods grown with the use of low or no synthetic chemical inputs. Mild strain cross-protection (MSCP), the pre-immunization of a plant using a mild strain of a virus to protect against subsequent infection by a severe strain of the virus, fits with future-proofing of production systems. New examples of MSCP use have occurred recently.

Superinfection exclusion by Citrus tristeza virus does not correlate with the production of viral small RNAs.

Superinfection exclusion (SIE), a phenomenon in which a preexisting viral infection prevents a secondary infection with the same or closely related virus, has been described for different viruses, including important pathogens of humans, animals, and plants. Several mechanisms acting at various stages of the viral life cycle have been proposed to explain SIE. Most cases of SIE in plant virus systems were attributed to induction of RNA silencing, a host defense mechanism that is mediated by small RNAs.

Dramatic Change in Citrus tristeza virus Populations in the Dominican Republic.

Citrus tristeza virus (CTV) is the most destructive viral pathogen of citrus and has been an important concern for the citrus industry in the Dominican Republic. Earlier studies documented widespread distribution of mild isolates of the T30 genotype, which caused no disease in the infected trees, and a low incidence of isolates of the VT and T3 genotypes, which were associated with economically damaging decline and stem-pitting symptoms in sweet orange and Persian lime, the two major citrus varieties grown in the Dominican Republic. In light of the dramatic increase in the number of severely diseased citrus trees throughout the country over the last decade, suggesting that field populations of CTV have changed, we examined the CTV pathosystem in the Dominican Republic to assess the dynamics of virus populations.

Loop-mediated isothermal amplification for the detection of plant pathogens.

Loop-mediated isothermal amplification (LAMP) is a technique involving the use of four to six primers (two inner primers, two outer primers, and two loop primers) and the strand displacement activity of Bacillus subtilis-derived (Bst) DNA polymerase. The end result of strand displacement and loop formation and synthesis is the single-temperature amplification of a highly specific fragment from a DNA template at a much greater titre than that obtained with polymerase chain reaction. With LAMP, there are several methods to determine a positive reaction.

Detection of Tomato black ring virus by real-time one-step RT-PCR.

A TaqMan-based real-time one-step RT-PCR assay was developed for the rapid detection of Tomato black ring virus (TBRV), a significant plant pathogen which infects a wide range of economically important crops. Primers and a probe were designed against existing genomic sequences to amplify a 72 bp fragment from RNA-2. The assay amplified all isolates of TBRV tested, but no amplification was observed from the RNA of other nepovirus species or healthy host plants.

Characterization of hydrangea chlorotic mottle virus, a new member of the genus Carlavirus.

An isolate of the tentative carlavirus species Hydrangea chlorotic mottle virus (HdCMV) was found in New Zealand (NZ) in 2007. The host range, serological properties and complete genome sequence of this isolate were determined in this study. While the NZ isolate shared 98% nucleotide sequence identity with the US isolate of HdCMV, differences in titre and host range were found.