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A probe-based quantitative PCR (qPCR) protocol was developed for detection and evaluation of the wheat bacterial leaf streak pathogen Xanthomonas translucens pv. undulosa (Xtu). The protocol can also detect X. translucens pv. translucens (Xtt), but can’t differentiate the two pathovars. When tested on DNA from plant, non-target bacteria and culture of microorganisms from wheat seeds, the qPCR showed a high specificity. On purified Xtu DNA, the qPCR was more sensitive than a loop-mediated isothermal amplification (LAMP) assay. When DNA samples from a set of serial dilutions of Xtu cells were tested, the qPCR method could repeatedly generate quantification cycle (Cq) values from the dilutions containing ≥1,000 cells. Since 2 µL of the total of 50 µL DNA was used in one reaction, one qPCR reaction could detect the presence of the bacteria in samples containing as few as 40 bacterial cells. The qPCR could detect the bacteria from both infected seed and leaf tissues. For seed testing, a protocol for template preparation was standardized, which allowed one qPCR reaction to test DNA from the surface of one seed. Thus, the qPCR system could theoretically detect Xtu and/or Xtt in samples where the bacteria had an average concentration ≥40 cells per seed.

Clubroot, caused by Plasmodiophora brassicae, is an important disease of canola and other brassica crops. Improved understanding of host and pathogen biology is frequently useful in guiding management strategies. In order to better understand infection thresholds, seven-day old seedlings of canola cultivar Westar were inoculated with serially diluted concentrations of P. brassicae resting spores. Controlled soil and plant inoculation assays were performed and the plants maintained in a greenhouse for 42 days and clubroot disease severity evaluated visually. Clubroot symptoms were observed in soils containing as low as one spore/mL soil and on plants inoculated with as few as ≤ 100 resting spores. These thresholds were lower than any previously reported. The results indicated the importance of highly sensitive detection methods for P. brassicae diagnosis and quantification methods for clubroot risk prediction in soils. Furthermore, these results highlighted the low probability of obtaining P. brassicae single spore isolates.

A simple and accurate PCR protocol for identification of Fusarium graminearum from fungal cultures was developed. In this protocol, DNA extraction was omitted by using the Thermo Scientific...

Tomato brown rugose fruit virus (ToBRFV) is a member of Tobamovirus infecting tomato and pepper. Within North America, both the United States and Mexico consider ToBRFV to be a regulated pest. In Canada, the presence of ToBRFV has been reported, but an efficient diagnostic system has not yet been established. Here, we describe the development and assessment of a loop-mediated isothermal amplification (LAMP)-based assay to detect ToBRFV. The LAMP test was efficient and robust, and results could be obtained within 35 min with an available RNA sample. Amplification was possible when either water bath or oven were used to maintain the temperature at isothermal conditions (65°C), and results could be read by visual observation of colour change. Detection limit of the LAMP was eight target RNA molecules. Under the experimental conditions tested, LAMP was as sensitive as qPCR and 100 times more sensitive than the currently used rt-PCR. We recommend this sensitive, efficient LAMP protocol to be used for routine lab testing of ToBRFV.