Real-Time PCR Quantification of Peronospora arborescens, the Opium Poppy Downy Mildew Pathogen, in Seed Stocks and Symptomless Infected Plants

In this study, we developed a reliable, quick, and accurate quantitative polymerase chain reaction (qPCR) assay based on the MIQE (Minimum Information for publication of Quantitative Real-Time PCR Experiments) guidelines for the quantification of Peronospora arborescens in infected downy mildew–symptomless opium poppy (Papaver somniferum) tissues and commercial seed stocks. The protocol was highly reproducible and allowed accurate quantification of pathogen DNA up to 10 fg in different plant DNA backgrounds without losing specificity and efficiency. Moreover, to further overcome difficulties conferred by the strict biotrophy of this pathogen, we developed dilution series of DNA extracted from a plasmid with the target pathogen DNA as a cloned insert. This facilitated the demonstration of the robustness of the protocol in different laboratories with different qPCR equipment and reagents, which may help in its use on a broad scale. Finally, we validated the usefulness of the qPCR protocol for quarantine purposes and downy mildew resistance screening by quantifying P. arborescens in complex, naturally infested opium poppy samples. Thus, a pathogen biomass of 0.0003 to 0.007‰ or of 0.110 to 5,557 ppm was quantified in symptomless capsules in commercial seed stocks, or in stem samples from symptomless opium poppy plants systemically infected by the pathogen, respectively.

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Quantitative Real-Time Polymerase Chain Reaction Detection of BK Virus Using Labeled Primers

Archives of Pathology & Laboratory Medicine ◽

10.5858/134.3.444 ◽

2010 ◽

Vol 134 (3) ◽

pp. 444-448 ◽

Cited By ~ 1

Author(s):

Zhengming Gu ◽

Jianmin Pan ◽

Matthew J. Bankowski ◽

Randall T. Hayden

Keyword(s):

Polymerase Chain Reaction ◽

Real Time ◽

Real Time Pcr ◽

Quantitative Polymerase Chain Reaction ◽

Bk Virus ◽

Clinical Samples ◽

Quantitative Detection ◽

Chain Reaction ◽

Pcr Method ◽

Polymerase Chain

Abstract Context.—BK virus infections among immunocompromised patients are associated with disease of the kidney or urinary bladder. High viral loads, determined by quantitative polymerase chain reaction (PCR), have been correlated with clinical disease. Objective.—To develop and evaluate a novel method for real-time PCR detection and quantification of BK virus using labeled primers. Design.—Patient specimens (n = 54) included 17 plasma, 12 whole blood, and 25 urine samples. DNA was extracted using the MagNA Pure LC Total Nucleic Acid Isolation Kit (Roche Applied Science, Indianapolis, Indiana); sample eluate was PCR-amplified using the labeled primer PCR method. Results were compared with those of a user-developed quantitative real-time PCR method (fluorescence resonance energy transfer probe hybridization). Results.—Labeled primer PCR detected less than 10 copies per reaction and showed quantitative linearity from 101 to 107 copies per reaction. Analytical specificity of labeled primer PCR was 100%. With clinical samples, labeled primer PCR demonstrated a trend toward improved sensitivity compared with the reference method. Quantitative assay comparison showed an R2 value of 0.96 between the 2 assays. Conclusions.—Real-time PCR using labeled primers is highly sensitive and specific for the quantitative detection of BK virus from a variety of clinical specimens. These data demonstrate the applicability of labeled primer PCR for quantitative viral detection and offer a simplified method that removes the need for separate oligonucleotide probes.

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Simultaneous One-Tube Quantification of Host and Pathogen DNA with Real-Time Polymerase Chain Reaction

Phytopathology ◽

10.1094/phyto.2002.92.1.112 ◽

2002 ◽

Vol 92 (1) ◽

pp. 112-116 ◽

Cited By ~ 83

Author(s):

L. M. Winton ◽

J. K. Stone ◽

L. S. Watrud ◽

E. M. Hansen

Keyword(s):

Polymerase Chain Reaction ◽

Real Time ◽

Fluorescent Dyes ◽

Quantitative Polymerase Chain Reaction ◽

Positive Control ◽

Douglas Fir ◽

Chain Reaction ◽

Taqman Probes ◽

Polymerase Chain ◽

Pathogen Dna

Phaeocryptopus gaeumannii is a widespread foliar parasite of Douglas-fir. Although normally innocuous, the fungus also causes the defoliating disease Swiss needle cast in heavily infected needles. The extent of P. gaeumannii colonization in Douglas-fir foliage was estimated with real-time quantitative polymerase chain reaction (PCR) using TaqMan chemistry. In order to derive a normalized expression of colonization, both pathogen and host DNA were simultaneously amplified but individually detected by species-specific primers and TaqMan probes labeled with different fluorescent dyes. Detection of host DNA additionally provided an endogenous reference that served as both an internal positive control and adjusted for variation introduced by sample-to-sample differences in DNA extraction and PCR efficiencies. The genes employed for designing the TaqMan probes and primers were β-tubulin for the pathogen and a LEAFY/FLORICAULA-like gene involved in floral development for the tree host. Both probe/primer sets exhibited high precision and reproducibility over a linear range of 4 orders of magnitude. This eliminated the need to analyze samples in multiple dilutions when comparing lightly with heavily infected needles. Quantification of the fungus within needles was successful as early as 1 month after initial infection. Real-time PCR is the only method currently available to quantify P. gaeumannii colonization early in the first year of the colonization process.

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Quantitative assessment of hematopoietic chimerism after bone marrow transplantation by real-time quantitative polymerase chain reaction

Blood ◽

10.1182/blood.v99.12.4618 ◽

2002 ◽

Vol 99 (12) ◽

pp. 4618-4625 ◽

Cited By ~ 238

Author(s):

Mehdi Alizadeh ◽

Marc Bernard ◽

Bruno Danic ◽

Charly Dauriac ◽

Brigitte Birebent ◽

...

Keyword(s):

Polymerase Chain Reaction ◽

Stem Cell ◽

Real Time ◽

Real Time Pcr ◽

Quantitative Assessment ◽

Quantitative Polymerase Chain Reaction ◽

Chain Reaction ◽

Hematopoietic Stem ◽

Pcr Method ◽

Polymerase Chain

We have developed a real-time quantitative polymerase chain reaction (PCR) assay using TaqMan technology (Applied Biosystems, Foster City, CA) for monitoring donor cell engraftment in allogenic hematopoietic stem cell transplant recipients. For this purpose, we selected 19 specific sequence polymorphisms belonging to 11 human biallelic loci located on 9 different chromosomes. Using a set of specially designed primers and fluorogenic probes, we evaluated the 19 markers' informativity on a panel of 126 DNA samples from 63 recipient/donor pairs. In more than 90% of these pairs, discrimination between recipient and donor genetic profile was possible. By using serial dilutions of mixed DNAs, we evaluated the linearity and sensitivity of the method. A linear correlation with rhigher than 0.98 and a sensitivity of 0.1% proved reproducible. Fluorescent-based PCR of short tandem repeats (STR-PCR) and real-time PCR chimerism assay were compared with a panel of artificial cell mixtures. The main advantage of the real-time PCR method over STR-PCR chimerism assays is the absence of PCR competition and plateau biases, and results evidenced greater sensitivity and linearity with the real-time PCR method. Furthermore, different samples can be tested in the same PCR run with a final result in fewer than 48 hours. Finally, we prospectively analyzed patients who received allografts and present 4 different clinical situations that illustrate the informativity level of our method. In conclusion, this new assay provides an accurate quantitative assessment of mixed chimerism that can be useful in guiding early implementation of additional treatments in hematopoietic stem cell transplantation.

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Real-time quantitative PCR detection ofEscherichia coliO157:H7

Chinese Journal of Agricultural Biotechnology ◽

10.1017/s1479236207001349 ◽

2007 ◽

Vol 4 (1) ◽

pp. 15-19 ◽

Cited By ~ 4

Author(s):

Chen Si ◽

Huang Kun-Lun ◽

Xu Wen-Tao ◽

Li Yuan ◽

Luo Yun-Bo

Keyword(s):

Real Time ◽

Real Time Pcr ◽

Quantitative Polymerase Chain Reaction ◽

Amplification Product ◽

Chain Reaction ◽

Standard Curve ◽

Real Time Quantitative Pcr ◽

Pcr Method ◽

Polymerase Chain ◽

Dissociation Curves

AbstractA rapid and accurate real-time quantitative polymerase chain reaction (real-time PCR) method with SYBR Green I was established for detectingEscherichia coliO157:H7. A pair of primers were designed to amplify theeaegene. The dissociation curves showed that the amplification product was very specific. The optimal conditions and standard curve were established. The result indicated that real-time PCR was 1000 times more sensitive than ordinary PCR.

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Evaluation method for asymmetric uncertainty of quantitative polymerase chain reaction measurements of deoxyribonucleic acids with low copy number

Scientific Reports ◽

10.1038/s41598-021-90959-0 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Unoh Ki ◽

Takeru Suzuki ◽

Satoshi Nakazawa ◽

Yuuki Yonekawa ◽

Kazuki Watanabe ◽

...

Keyword(s):

Polymerase Chain Reaction ◽

Confidence Interval ◽

Real Time ◽

Real Time Pcr ◽

Copy Number ◽

Limit Of Detection ◽

Quantitative Polymerase Chain Reaction ◽

Chain Reaction ◽

Low Copy Number ◽

Polymerase Chain

AbstractRecently, in food safety and various other fields, qualitative and quantitative gene analysis using real-time polymerase chain reaction (PCR) method has become increasingly popular. The limit of detection (LOD) and quantifiable range for these measurements depends on the range and precision of DNA calibrators’ concentrations. Low-copy-number nucleic acid reference materials with low uncertainty produced by an inkjet system have been developed to allow for precise measurements in a low-copy-number region. However, when using a calibrator with a low copy number near one, the copy number distribution is asymmetric. Consequently, the confidence intervals of estimated copy numbers can include negative values when conventional methods of uncertainty estimation are used. A negative confidence interval is irrelevant in the context of copy number, which is always positive value or zero. Here, we propose a method to evaluate the uncertainty of real-time PCR measurements with representative values and an asymmetric 95% confidence interval. Moreover, we use the proposed method for the actual calculation of uncertainty of real-time PCR measurement results for low-copy-number DNA samples and demonstrate that the proposed method can evaluate the precision of real-time PCR measurements more appropriately in a low-copy-number region.

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Optimization of 6-carboxy-X-rhodamine concentration for real-time polymerase chain reaction using molecular beacon chemistry

Canadian Journal of Microbiology ◽

10.1139/w06-145 ◽

2007 ◽

Vol 53 (3) ◽

pp. 391-397 ◽

Cited By ~ 4

Author(s):

Gehua Wang ◽

Erin Becker ◽

Christine Mesa

Keyword(s):

Polymerase Chain Reaction ◽

Real Time ◽

Real Time Pcr ◽

Molecular Beacon ◽

Quantitative Polymerase Chain Reaction ◽

Luxs Gene ◽

Chain Reaction ◽

Pcr Assay ◽

Shiga Toxin 2 ◽

Polymerase Chain

The optimal 6-carboxy-X-rhodamine (ROX) concentration, which is used as a passive reference dye for real-time quantitative polymerase chain reaction (PCR) with molecular beacon chemistry, was determined with the Mx4000™ Multiplex Quantitative PCR System. Additionally, the effects of changing ROX concentrations on PCR reproducibility, Ct values, and efficiency were investigated with this system by using the PCR data obtained from amplification of the Escherichia coli shiga toxin 2 (stx2) gene and the Campylobacter jejuni luxS gene. This study indicated that different ROX concentrations influence many aspects of the real-time PCR reaction. ROX concentration variation could have consequences in the analysis of quantitative data and may lead to erroneous results. This study further indicated that the optimal ROX concentration is 60 nmol/L for real-time PCR, using molecular beacon chemistry for PCR assay of luxS and stx2 genes.

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Development of a Real-Time Polymerase Chain Reaction Assay for Quantifying Verticillium albo-atrum DNA in Resistant and Susceptible Alfalfa

Phytopathology ◽

10.1094/phyto-97-11-1519 ◽

2007 ◽

Vol 97 (11) ◽

pp. 1519-1525 ◽

Cited By ~ 20

Author(s):

R. C. Larsen ◽

G. J. Vandemark ◽

T. J. Hughes ◽

C. R. Grau

Keyword(s):

Polymerase Chain Reaction ◽

Real Time ◽

Disease Severity ◽

Verticillium Wilt ◽

Real Time Pcr ◽

Severity Index ◽

Disease Severity Index ◽

Chain Reaction ◽

Polymerase Chain ◽

Pathogen Dna

A precise real-time polymerase chain reaction (PCR) assay was developed for quantifying Verticillium albo-atrum DNA. The assay was used in a repeated experiment to examine the relationship between the quantity of pathogen DNA detected in infected leaves and shoots and the severity of Verticillium wilt symptoms in several alfalfa cultivars expressing a range of disease symptoms. Plants were visually inspected for symptoms and rated using a disease severity index ranging from 1 to 5, and the quantity of pathogen DNA present in leaves and stems was determined with real-time PCR. No significant differences in pathogen DNA quantity or disease severity index were observed for experiments or for cultivar–experiment interactions. Significant differences were observed between cultivars for the quantity of pathogen DNA detected with real-time PCR and also for disease severity index ratings. In both experiments, the highly resistant check cultivar Oneida VR had significantly less pathogen DNA, and significantly lower disease severity index ratings than the resistant cultivar Samauri, the moderately resistant cultivar Vernema, and the susceptible check cultivar Saranac. In both experiments, the Spearman rank correlation between the amount of V. albo-atrum DNA detected in leaves and stems with real-time PCR and disease severity index ratings based on visual examination of symptoms was positive (>0.52) and significant (P < 0.0001). These results suggest that resistance to Verticillium wilt in alfalfa is characterized by a reduced colonization of resistant genotypes by the fungus.

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Analysis and validation of a highly sensitive one-step nested quantitative real-time polymerase chain reaction assay for specific detection of severe acute respiratory syndrome coronavirus 2

Virology Journal ◽

10.1186/s12985-020-01467-y ◽

2020 ◽

Vol 17 (1) ◽

Author(s):

Yang Zhang ◽

Chunyang Dai ◽

Huiyan Wang ◽

Yong Gao ◽

Tuantuan Li ◽

...

Keyword(s):

Polymerase Chain Reaction ◽

Real Time ◽

Quantitative Polymerase Chain Reaction ◽

Clinical Samples ◽

Chain Reaction ◽

Pcr Assay ◽

Qrt Pcr ◽

Highly Sensitive ◽

One Step ◽

Polymerase Chain

Abstract Background Coronavirus disease 2019 (COVID-19), caused by SARS-CoV-2, is posing a serious threat to global public health. Reverse transcriptase real-time quantitative polymerase chain reaction (qRT-PCR) is widely used as the gold standard for clinical detection of SARS-CoV-2. Due to technical limitations, the reported positive rates of qRT-PCR assay of throat swab samples vary from 30 to 60%. Therefore, the evaluation of alternative strategies to overcome the limitations of qRT-PCR is required. A previous study reported that one-step nested (OSN)-qRT-PCR revealed better suitability for detecting SARS-CoV-2. However, information on the analytical performance of OSN-qRT-PCR is insufficient. Method In this study, we aimed to analyze OSN-qRT-PCR by comparing it with droplet digital PCR (ddPCR) and qRT-PCR by using a dilution series of SARS-CoV-2 pseudoviral RNA and a quality assessment panel. The clinical performance of OSN-qRT-PCR was also validated and compared with ddPCR and qRT-PCR using specimens from COVID-19 patients. Result The limit of detection (copies/ml) of qRT-PCR, ddPCR, and OSN-qRT-PCR were 520.1 (95% CI: 363.23–1145.69) for ORF1ab and 528.1 (95% CI: 347.7–1248.7) for N, 401.8 (95% CI: 284.8–938.3) for ORF1ab and 336.8 (95% CI: 244.6–792.5) for N, and 194.74 (95% CI: 139.7–430.9) for ORF1ab and 189.1 (95% CI: 130.9–433.9) for N, respectively. Of the 34 clinical samples from COVID-19 patients, the positive rates of OSN-qRT-PCR, ddPCR, and qRT-PCR were 82.35% (28/34), 67.65% (23/34), and 58.82% (20/34), respectively. Conclusion In conclusion, the highly sensitive and specific OSN-qRT-PCR assay is superior to ddPCR and qRT-PCR assays, showing great potential as a technique for detection of SARS-CoV-2 in patients with low viral loads.

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