Xanthomonas fragariae is the causal agent of angular leaf spot of strawberry. Short-read sequences were generated for two X. fragariae strains with different virulence phenotypes on the Illumina HiSeq 2000 platform. The genome sequences will contribute to a better understanding of pathogen evolution and the genes contributing to virulence in X. fragariae .
Most molecular diagnostic assays are designed to detect the simple presence of a protein or nucleic acid without regard to whether that protein or nucleic acid originated from a viable and presumably pathogenic organism at the time of isolation. We recently developed a viable-cell detection assay (propidium monoazide [PMA]-qPCR) for specific detection of viable (living) cells of Xanthomonas fragariae, the pathogen causing angular leaf spot of strawberry, and herein describe a unique set of statistical analyses for validation of this assay. For any detection assay or test, calculation of its sensitivity and specificity is essential for determining its diagnostic capabilities, particularly when evaluating competing assays or tests. This is often achieved by running competing tests concurrently on a set of samples with known pathogen density or disease status and cross-tabulating results. However, the PMA-qPCR assay is unique among PCR-based diagnostics because it is designed specifically to detect DNA from living cells only, whereas most traditional PCR assays are designed to detect DNA from the target organism regardless of its state of viability. Thus, one cannot directly compare the results from a cell-viability assay with those from a general assay to gauge the performance of either assay because the assays target two different but overlapping populations (i.e., the viable-cell population and the viable- plus nonviable-cell population). To address this challenge, two standard statistical approaches to diagnostic test evaluation were used jointly to estimate the test performance of the PMA-qPCR assay relative to two common assays for detection of X. fragariae. In both analyses, the PMA-qPCR outperformed the qPCR for detection of viable cells under a range of conditions. Viability testing is extremely useful in certification and disease management applications, and with the information on test performance generated here, the test can be put to practical use to design sampling strategies to account for the errors in testing. [Formula: see text] The author(s) have dedicated the work to the public domain under the Creative Commons CC0 “No Rights Reserved” license by waiving all of his or her rights to the work worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law, 2023.
Heat treatment has been shown to be an effective method for reducing systemic pathogens in strawberry but the process often has adverse effects on plant health. Research has shown that a brief heat treatment of plants at a lower temperature prior to the main heat treatment can induce heat shock proteins, which serve to protect the plant from damage when treated at higher temperatures. The objective of this study was to determine the relative gene expression of two heat shock factors (HSFs) and eight heat shock proteins (HSPs) in two strawberry cultivars (Festival and Ventana) known to have differential tolerance to heat. Strawberry plants were treated at 37 °C for 1 hour to induce the heat shock response. Total RNA was extracted and reverse transcription polymerase chain reaction (RT-PCR) was used to determine the amount of target produced. Relative gene expression was determined using the 2−∆∆ct method. Results showed that transcripts of one HSF and five HSPs were significantly more abundant in cv. Festival (p < 0.05) but transcripts from only one gene, sHsp15.96, were significantly more abundant in cv. Ventana. Results of this study have identified gene candidates that may confer heat tolerance in strawberry, which may be useful for selecting heat tolerant plants in breeding programs.
In this work, lightweight and robust Ti 3 C 2 T x /CNTs foams were fabricated by a HCl induced self-assembly as well as vacuum freeze-drying process. In contrast to monolithic Ti 3 C 2 T x foams, the incorporation of CNTs effectively improves the electrical conductivity (EC) and mechanical elasticity of the foam, prevents the stacking of Ti 3 C 2 T x nanosheets and produces a more developed 3D honeycomb-like porous network structure, which dramatically ameliorate impedance matching and enhance the multiple reflection, conduction loss and interface polarization, and jointly lead to a superb microwave absorption performance. By immersing it into the melted paraffin and cutting into coaxial ring samples, an optimum RL of -48.8 dB (1.72 mm) and a maximum EAB of 5.44 GHz (1.92 mm) were obtained when loading 4wt% absorber. Moreover, the EAB could be regulated from 4.16 GHz to 18 GHz as the thickness increases from 1.52 mm to 4.92 mm. This work provides a facile strategy for constructing lightweight and robust Ti 3 C 2 T x /CNTs foams, conforming the combined pursuit of light weight, thin thickness, broad EAB and intense dissipation capability for microwave absorption materials (MAMs).
Abstract Helicoverpa armigera (Hübner) is a major crop pest native to Europe, Asia, Australia, and Africa which has recently invaded South America and has caused billions of dollars in agricultural losses. Because of challenges in differentiating between H. armigera and Helicoverpa zea (Boddie), a closely related species native to North and South America, genetic tests have previously been developed to detect H. armigera DNA in pooled samples of moth legs. In this study, a field-based recombinase polymerase amplification (RPA) assay using a lateral flow strip and a qPCR melt curve assay were developed for specific detection of H. armigera DNA in pooled moth samples. In addition, a crude DNA extraction protocol for whole moths was developed to allow rapid preparation of DNA samples. The RPA field test was able to detect ≥ 10 pg of purified H. armigera DNA and the crude DNA of one H. armigera sample in a background of 999 H. zea equivalents. The qPCR assay was able to detect ≥ 100 fg of purified H. armigera DNA and the crude DNA of one H. armigera sample in a background of up to 99,999 H. zea equivalents. Both RPA and qPCR assays detected H. armigera in the crude DNA extracted in the field from a pool of one H. armigera moth and 999 H. zea moths. These newly developed molecular assays to detect H. armigera will contribute to large-scale surveillance programs of H. armigera.
Abstract Frankliniella fusca Hinds (Thysanoptera: Thripidae) is an economically important pest of many cultivated crops including cotton, tomatoes, peppers and tobacco. Previous research has focused on the importance of non‐crop weeds for F. fusca populations when estimating crop infestation risk in the spring. Although weeds play an integral role in population development, early‐season cultivated hosts (e.g. wheat and sage) may also contribute and augment overall populations. Few studies have examined the role of early‐season crops as a source habitat for sensitive host crops later in the season. The goal of this study was to investigate the abiotic conditions and landscape components that are associated with F. fusca populations in winter wheat ( Triticum aestivum L.). Exploring these relationships will provide insight into early‐season drivers of F. fusca . To do this, we conducted a 2 year study documenting F. fusca populations during an 8 weeks period each spring. We sampled immature thrips abundance on wheat heads while concurrently monitoring adult dispersal from the field using yellow sticky cards. Across both years, we found that immature thrips sampled during the milk and dough development stages best‐predicted adult dispersal 2 weeks later. Cumulative precipitation and the number of precipitation events beginning in the autumn of the prior year were the most important abiotic predictors of F. fusca abundance. At the landscape scale, adult F. fusca density was negatively related to the area of row crop agriculture, grasslands and amount of landscape fragmentation. Results of our study provide a basis to assess larval thrips and forecast dispersal of this pest from wheat using a head sampling method. At a landscape scale, we show that specific combinations of abiotic and landscape variables influence population abundance of F. fusca in North Carolina row crop agroecosystems.
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