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Species-specific endogenous reference sequences are indispensable in the development of methods to detect genetically modified (GM) crops for food and feed. We analyzed a partial sequence derived from the β-fructosidase gene among several solanaceous species and developed a new eggplant specific detection method using loop-mediated isothermal amplification (LAMP). LAMP is a rapid, specific, and cost-effective technique. The species-specificity and stability of the developed method were evaluated using 18 eggplant cultivars and other crops including solanaceous plants. The limit of detection was also evaluated. The developed method showed high specificity for eggplants and stability among the eggplant cultivars tested. These results suggested that the developed method would be useful as a positive control for the detection of GM eggplants with LAMP.

Agrobacterium-mediated transformation is the most commonly used technique for plant genetic engineering. During the transformation, a T-DNA region, which is flanked by the right border (RB) and the left border, is transferred to plant nuclear chromosomes. Simultaneously, a sequence adjacent to the RB on T-DNA is frequently transferred to plant genomes together with the intentionally introduced recombinant DNA. We developed a novel polymerase chain reaction (PCR)-mediated detection method targeting this region. The conserved sequence of the region found in genetically modified (GM) crops is only 25 bp in length. To detect this ultrashort 25 bp sequence near the RB region, we designed a primer set consisting of a 12-base forward primer and a 13-base reverse primer. The predicted band was detected from GM crops by optimizing the PCR conditions. We used lateral flow DNA chromatography for rapid and inexpensive detection. The developed method would be applicable for screening the GM crops generated by Agrobacterium-mediated transformation.

Johne’s disease (JD) is an economically important infectious disease in livestock farming caused by Mycobacterium avium subsp. paratuberculosis. As an alternative to serological tests, which are used mainly for the screening of whole herds, we developed a novel ResoLight-based real-time PCR (RL-PCR) assay with pooled fecal samples for the detection of fecal shedders in cattle herds. The RL-PCR assay included an internal amplification control (IC) which was amplified using the same primer pair as the target molecule M. avium subsp. paratuberculosis IS900 and differentiated based on melting temperatures. Individual fecal suspensions were pooled and concentrated by centrifugation to avoid a loss of sensitivity by the dilution effect. Combined with a DNA extraction kit (Johne-PureSpin; FASMAC), no inhibition of PCR amplification was observed with up to 15 fecal samples in a pool. The detection limit of RL-PCR at a pool size of 10 was 10 M. avium subsp. paratuberculosis organisms per gram of feces, which was comparable to that of individual testing. A total of 2,654 animals in 12 infected herds were screened by individual antibody-enzyme-linked immunosorbent assay (ELISA) and the RL-PCR assay using pooled feces. Fifty animals were diagnosed with JD through the screening by RL-PCR, compared with only 5 by ELISA (which were also positive in RL-PCR). In 7 JD-free herds, the results of 4 out of 327 pools (1.2%) were invalid due to the lack of IC amplification, and then animals were confirmed negative individually. Our results suggest that implementation of herd screening by pooled RL-PCR would advance the monitoring and control of JD in cattle herds.

The identification of insect species is generally achieved by analyzing the specific morphological characteristics or, in more recent years, by polymerase chain reaction (PCR) assays of DNA sequences. PCR assays, which detect specific segments of DNA, have been established as a highly sensitive method for a wide range of applications, including the verification of hereditary diseases and for criminal investigations. For the identification of insects, the CO1 (cytochrome c oxidase subunit I) gene of mitochondrial (mt) DNA is often used. However, analyses of the entire mtDNA sequence might yield more reliable regions for use in the identification of insect species. Here we developed a method for real-time PCR identification of the khapra beetle, Trogoderma granarium Everts, by comparing the whole mtDNA sequences of three species of dermestid beetle: the khapra beetle, the varied carpet beetle, Anthrenus verbasci (L.), and the black carpet beetle, Attagenus unicolor japonicus Reitter. Several khapra beetle-specific mtDNA regions were identified and selected for use in the real-time PCR identification of these beetles based on Taq-Man® chemistry. Specificity tests conducted with the DNAs of several insects, including those of the three beetles described above, revealed that the primer/probe sets designed for the real-time PCR were highly specific to their targets.

We developed new loop-mediated isothermal amplification (LAMP)-based detection methods for the screening of genetically modified (GM) maize and soybean events. The LAMP methods developed targeted seven sequences: cauliflower mosaic virus 35S promoter; 5-enolpyruvylshikimate-3-phosphate synthase gene from Agrobacterium tumefaciens strain CP4 (cp4epsps); phosphinothricin acetyltransferase (pat) gene; mannose-6-phosphate isomerase gene; Pisum sativum ribulose 1, 5-bisphosphate carboxylase terminator; a common sequence between Cry1Ab and Cry1Ac genes; and a GA21 construct-specific sequence. We designed new specific primer sets for each target, and the limit of detection (LOD) was evaluated using authorized GM maize and soybean events. LODs for each target were ≤ 0.5%. To make the DNA extraction process simple and rapid, we also developed a direct LAMP detection scheme using crude cell lysates. The entire process, including pretreatments and detection, could be completed within 1 h.

Kudoa septempunctata is the causative agent of a food-borne disease associated with the ingestion of raw olive flounder. As the current qRT-PCR method for its detection is time-consuming, a rapid and simple method is required. Recently, a new real-time loop-mediated isothermal amplification (LAMP) method and an immunochromatography method, whose sensitivities are intended to be compatible with that designated in the official analytical method (10(5) spores/g olive flounder), have been developed. To validate these new methods, we performed an inter-laboratory study across seven laboratories. Both methods could not detect less than 10(4) spores/g; however, these methods were able to detect more than 10(5) spores/g in olive flounder samples. These results demonstrated that the sensitivities of these methods were compatible with the designated level in the official analytical method. We concluded that these new methods were acceptable as the screening methods for K. septempunctata.

We developed a novel loop-mediated isothermal amplification (LAMP)-based detection method using lateral flow dipstick chromatography for genetically modified (GM) soybean and maize events. The single-stranded tag hybridization (STH) for the chromatography printed-array strip (C-PAS) system was used for detections targeting the cauliflower mosaic virus 35S promoter, mannose-6-phosphate isomerase gene, Pisum sativum ribulose 1, 5-bisphosphate carboxylase terminator, a common sequence between the Cry1Ab and Cry1Ac genes, and a GA21-specific sequence. The STH C-PAS system was applicable for multiplex analyses to perform simultaneous detections. The limit of detection was 0.5% or less for each target. By using the developed method, the LAMP amplification was visually detected. Moreover, the detection could be carried out without any expensive instruments, even for the DNA amplification steps, by virtue of the isothermal reaction. We demonstrated that the rapid and useful method developed here would be applicable for screening GM crops.

Species-specific endogenous reference sequences are indispensable in the development of methods to detect genetically modified (GM) crops and food/feed. We evaluated and compared the applicability of 6 rice (Oryza sativa) endogenous sequences, including 5 previously reported sequences; SPS1 derived from the sucrose phosphate synthase (SPS) gene, PLD1 and PLD2 derived from the phospholipase D (PLD) gene, GOS9 derived from the root-specific gene gos9, and ppi-PPF derived from the ppi-phosphofructokinase (ppi-PPF) gene, as well as a newly designed sequence, SPS2 in the rice SPS gene promoter region. PCR efficiency and stability were evaluated with 28 rice cultivars, and species specificity was evaluated using gDNAs isolated from major crops and rice-related species. SPS1 and GOS9 were less easy to be amplified and showed lower PCR amplification stabilities than the other sequences among rice cultivars. On the other hand, PLD1 showed high PCR efficiency and stability but low specificity against rice. Meanwhile, ppi-PPF was moderate in all evaluated characteristics. SPS2 and PLD2 showed higher PCR efficiencies and stabilities than those of other sequences, and also had acceptable species specificities. We conclude that SPS2 and PLD2 are ideal endogenous sequences for use in the development of methods to detect and quantify GM rice.

Stacked genetically modified (GM) maize is increasingly produced; thereby, current event-specific quantitative real-time polymerase chain reaction (qPCR) methods have led to the overestimation of GM organism (GMO) content compared with the actual weight/weight percentage of GM organism in maize samples. We developed a feasible qPCR method in which the GMO content is calculated based on the quantification of two herbicide-tolerant trait genes, 5-enolpyruvylshikimate-3-phosphate synthase from Agrobacterium sp. strain CP4 (cp4epsps) and phosphinothricin N-acetyl-transferase from Streptomyces viridochromogenes (pat) to quantify the GMO content in ground grain samples containing stacked GM maize. The GMO contents of two genes were quantified using a plasmid calibrant and summed for quantification of total GMO content. The trait-specific method revealed lower biases for examination of test samples containing stacked GM maize compared with the event-specific method. Our results clearly show that the trait-specific method is not only simple and cost-effective, but also useful in quantifying the GMO content in ground grain samples containing stacked GM maize, which are expected to be major events in the near future. The developed method would be the only feasible way to conduct the quantification of GMO content in the ground maize samples containing stacked GM maize for the verification of the labeling regulation.

To improve the efficiency of DNA analysis of foods and agricultural products, we investigated a direct real-time PCR based on the real-time monitoring of DNA amplification directly from crude cell lysates of analytical samples. We established a direct real-time PCR system comprising sample pretreatment with a specified lysis buffer and real-time PCR using the developed master mix reagent. No PCR inhibition was observed in the analysis of crude cell lysates from 50 types of samples, indicating that the direct real-time PCR system is applicable to a wide range of materials. The specificity of the direct real-time PCR was evaluated by means of a model assay system for single nucleotide discrimination. Even when crude cell lysates coexisted in the reaction mixtures, the primer selectivity was not affected, suggesting that the sequence specificity of the direct real-time PCR was equivalent to that of PCR from purified DNA templates. We evaluated the sensitivity and quantitative performance of the direct real-time PCR using soybean flour samples including various amounts of genetically modified organisms. The results clearly showed that the direct real-time PCR system provides sensitive detection and precise quantitation.

A real-time PCR-based analytical method was developed for the event-specific quantification of a genetically modified (GM) soybean event, MON87701. First, a standard plasmid for MON87701 quantification was constructed. The conversion factor (C

Kudoa septempunctata is the causative agent of a food-borne disease associated with the ingestion of raw olive flounder. As the current qRT-PCR method for its detection is time-consuming, a rapid and simple method is required. Recently, a new real-time loop-mediated isothermal amplification (LAMP) method and an immunochromatography method, whose sensitivities are intended to be compatible with that designated in the official analytical method (10(5) spores/g olive flounder), have been developed. To validate these new methods, we performed an inter-laboratory study across seven laboratories. Both methods could not detect less than 10(4) spores/g; however, these methods were able to detect more than 10(5) spores/g in olive flounder samples. These results demonstrated that the sensitivities of these methods were compatible with the designated level in the official analytical method. We concluded that these new methods were acceptable as the screening methods for K. septempunctata.

Sarcocystis fayeri (S. fayeri) is a newly identified causative agent of foodborne disease that is associated with the consumption of raw horse meat. The testing methods prescribed by the Ministry of Health, Labour and Welfare of Japan are time consuming and require the use of expensive equipment and a high level of technical expertise. Accordingly, these methods are not suitable for use in the routine sanitary control setting to prevent outbreaks of foodborne disease. In order to solve these problems, we have developed a new, rapid and simple testing method using LAMP, which takes only 1 hour to perform and which does not involve the use of any expensive equipment or expert techniques. For the validation of this method, an inter-laboratory study was performed among 5 institutes using 10 samples infected with various concentrations of S. fayeri. The results of the inter-laboratory study demonstrated that our LAMP method could detect S. fayeri at concentrations greater than 10(4) copies/g. Thus, this new method could be useful in screening for S. fayeri as a routine sanitary control procedure.

A novel real-time PCR-based analytical method was developed for the event-specific quantification of a genetically modified (GM) maize, 3272. We first attempted to obtain genome DNA from this maize using a DNeasy Plant Maxi kit and a DNeasy Plant Mini kit, which have been widely utilized in our previous studies, but DNA extraction yields from 3272 were markedly lower than those from non-GM maize seeds. However, lowering of DNA extraction yields was not observed with GM quicker or Genomic-tip 20/G. We chose GM quicker for evaluation of the quantitative method. We prepared a standard plasmid for 3272 quantification. The conversion factor (Cf), which is required to calculate the amount of a genetically modified organism (GMO), was experimentally determined for two real-time PCR instruments, the Applied Biosystems 7900HT (the ABI 7900) and the Applied Biosystems 7500 (the ABI7500). The determined Cf values were 0.60 and 0.59 for the ABI 7900 and the ABI 7500, respectively. To evaluate the developed method, a blind test was conducted as part of an interlaboratory study. The trueness and precision were evaluated as the bias and reproducibility of the relative standard deviation (RSDr). The determined values were similar to those in our previous validation studies. The limit of quantitation for the method was estimated to be 0.5% or less, and we concluded that the developed method would be suitable and practical for detection and quantification of 3272.

We investigated the GM maize grain content of non-identity preserved (non-IP) maize samples produced in 2009 in the USA using our individual kernel detection system, involving two multiplex qualitative PCR methods coupled to microchip electrophoresis and partially real-time PCR array analysis, to clarify how many GM event maize grains were present in the samples and which GM events frequently appeared in 2009. The average percentage and standard deviation of GM maize grains on a kernel basis in five non-IP sample lots were 81.9%±2.8%, the average percentage of single GM event grains was 46.9%, and the average percentage of stacked GM event grains was 35.0%. MON88017 grains and NK603 grains were the most frequently observed as single GM event grains. The most frequent stacked GM event grains were MON88017×MON810 grains. This study shows that our method can provide information about GM maize events present in imported maize samples on a kernel basis.

Because of the increasing use of maize hybrids with genetically modified (GM) stacked events, the established and commonly used bulk sample methods for PCR quantification of GM maize in non-GM maize are prone to overestimate the GM organism (GMO) content, compared to the actual weight/weight percentage of GM maize in the grain sample. As an alternative method, we designed and assessed a group testing strategy in which the GMO content is statistically evaluated based on qualitative analyses of multiple small pools, consisting of 20 maize kernels each. This approach enables the GMO content evaluation on a weight/weight basis, irrespective of the presence of stacked-event kernels. To enhance the method's user-friendliness in routine application, we devised an easy-to-use PCR-based qualitative analytical method comprising a sample preparation step in which 20 maize kernels are ground in a lysis buffer and a subsequent PCR assay in which the lysate is directly used as a DNA template. This method was validated in a multilaboratory collaborative trial.

Quantitative and qualitative methods based on PCR have been developed for genetically modified organisms (GMO). Interlaboratory studies were previously conducted for GMO quantitative methods; in this study, an interlaboratory study was conducted for a qualitative method for a GM soybean, Roundup Ready® soy (RR soy), with primer pairs designed for the quantitative method of RR soy studied previously. Fourteen laboratories in Japan participated. Each participant extracted DNA from 1.0 g each of the soy samples containing 0, 0.05, and 0.10% of RR soy, and performed PCR with primer pairs for an internal control gene (Le1) and RR soy followed by agarose gel electrophoresis. The PCR product amplified in this PCR system for Le1 was detected from all samples. The sensitivity, specificity, and false-negative and false-positive rates of the method were obtained from the results of RR soy detection. False-negative rates at the level of 0.05 and 0.10% of the RR soy samples were 6.0 and 2.3%, respectively, revealing that the LOD of the method was somewhat below 0.10%. The current study demonstrated that the qualitative method would be practical for monitoring the labeling system of GM soy in kernel lots.

A novel real-time PCR-based analytical method was developed for the event-specific quantification of a genetically modified (GM) soybean event; A2704-12. During the plant transformation, DNA fragments derived from pUC19 plasmid were integrated in A2704-12, and the region was found to be A2704-12 specific. The pUC19-derived DNA sequences were used as primers for the specific detection of A2704-12. We first tried to construct a standard plasmid for A2704-12 quantification using pUC19. However, non-specific signals appeared with both qualitative and quantitative PCR analyses using the specific primers with pUC19 as a template, and we then constructed a plasmid using pBR322. The conversion factor (C(f)), which is required to calculate the amount of the genetically modified organism (GMO), was experimentally determined with two real-time PCR instruments, the Applied Biosystems 7900HT and the Applied Biosystems 7500. The determined C(f) values were both 0.98. The quantitative method was evaluated by means of blind tests in multi-laboratory trials using the two real-time PCR instruments. The limit of quantitation for the method was estimated to be 0.1%. The trueness and precision were evaluated as the bias and reproducibility of relative standard deviation (RSD(R)), and the determined bias and RSD(R) values for the method were each less than 20%. These results suggest that the developed method would be suitable for practical analyses for the detection and quantification of A2704-12.

The herbicide-tolerant genetically modified Roundup Ready canola (Brassica napus) line RT73 has been approved worldwide for use in animal feed and human food. However, RT73 Brassica rapa lines derived from interspecific crosses with RT73 B. napus have not been approved in Japan. Here, we report on a novel system using individual kernel analyses for the qualitative detection of RT73 B. rapa in canola grain samples. We developed a duplex real-time polymerase chain reaction (PCR) method to discriminate B. napus and B. rapa DNA using scatter plots of the end-point analyses; this method was able to discriminate a group comprising B. rapa and Brassica juncea from a group comprising B. napus, Brassica carinata, and Brassica oleracea. We also developed a duplex real-time PCR method for the simultaneous detection of an RT73-specific sequence and an endogenous FatA gene. Additionally, a DNA-extraction method using 96-well silica-membrane plates was developed and optimized for use with individual canola kernels. Our detection system could identify RT73 B. rapa kernels in canola grain samples enabling the accurate and reliable monitoring of RT73 B. rapa contamination in canola, thus playing a role in its governmental regulation in Japan.

Novel real-time PCR-based quantitative methods were developed for three GM maize events; MON863, NK603 and TC1507. The quantitative methods were designed to amplify an event-specific segment for MON863 and NK603, and a construct-specific segment for TC1507. We also developed an event-specific quantitative method for T25. The conversion factor (Cf), which is required for calculating the GMO amount, was determined using three types of real-time PCR equipment; the ABI PRISM 7700,7900HT and 7500. The quantitative methods were evaluated by blind testing in an interlaboratory study using the ABI PRISM 7700 and 7900HT, and in a multilaboratory trial using the ABI PRISM 7500. The trueness, precision, and limit of quantitation were determined. Although the biases expressing the trueness for MON863, TC1507, and T25 were slightly high, all the data suggested that the developed methods were suitable for identification and quantification of these GM maize events.

Polypropylene microtubes (tubes) are generally used for bio-material tests in addition to PCR tests such as genetically modified organism (GMO) testings. However, the choice of suitable tubes is quite important, because it might influence the results: DNA binding and/or elution of chemical substances sometimes occurs. In this study, we established methods to select tubes with the most suitable characteristics for DNA testing.

A novel real-time PCR-based analytical method was established for the event-specific quantification of a GM soybean event MON89788. The conversion factor (C(f)) which is required to calculate the GMO amount was experimentally determined. The quantitative method was evaluated by a single-laboratory analysis and a blind test in a multi-laboratory trial. The limit of quantitation for the method was estimated to be 0.1% or lower. The trueness and precision were evaluated as the bias and reproducibility of the relative standard deviation (RSD(R)), and the determined bias and RSD(R) values for the method were both less than 20%. These results suggest that the established method would be suitable for practical detection and quantification of MON89788.

A duplex real-time PCR method was developed for quantitative screening analysis of GM maize. The duplex real-time PCR simultaneously detected two GM-specific segments, namely the cauliflower mosaic virus (CaMV) 35S promoter (P35S) segment and an event-specific segment for GA21 maize which does not contain P35S. Calibration was performed with a plasmid calibrant specially designed for the duplex PCR. The result of an in-house evaluation suggested that the analytical precision of the developed method was almost equivalent to those of simplex real-time PCR methods, which have been adopted as ISO standard methods for the analysis of GMOs in foodstuffs and have also been employed for the analysis of GMOs in Japan. In addition, this method will reduce both the cost and time requirement of routine GMO analysis by half. The high analytical performance demonstrated in the current study would be useful for the quantitative screening analysis of GM maize. We believe the developed method will be useful for practical screening analysis of GM maize, although interlaboratory collaborative studies should be conducted to confirm this.

A novel real-time PCR-based analytical method was developed for the event-specific quantification of a genetically modified (GM) maize event, MIR162. We first prepared a standard plasmid for MIR162 quantification. The conversion factor (Cf) required to calculate the genetically modified organism (GMO) amount was empirically determined for two real-time PCR instruments, the Applied Biosystems 7900HT (ABI7900) and the Applied Biosystems 7500 (ABI7500) for which the determined Cf values were 0.697 and 0.635, respectively. To validate the developed method, a blind test was carried out in an interlaboratory study. The trueness and precision were evaluated as the bias and reproducibility of relative standard deviation (RSDr). The determined biases were less than 25% and the RSDr values were less than 20% at all evaluated concentrations. These results suggested that the limit of quantitation of the method was 0.5%, and that the developed method would thus be suitable for practical analyses for the detection and quantification of MIR162.

Qualitative PCR methods for the genetically modified (GM) maize events MON810, Bt11, and GA21, and the 35S promoter (P35S) region of the cauliflower mosaic virus (CaMV) were evaluated in an interlaboratory study. Real-time PCR-based quantitative methods for these GM events using the same primer pairs had already been validated in previous studies. Fifteen laboratories in Japan participated in this interlaboratory study. Each participant extracted DNA from blind samples, performed qualitative PCR assays, and then detected the PCR products with agarose gel electrophoresis. The specificity, sensitivity, and false-negative and false-positive rates of these methods were determined with different concentrations of GM mixing samples. LODs of these methods for MON810, Bt11, GA21, and the P35S segment calculated as the amount of MON810 were 0.2, 0.2, 0.1, and 0.2% or less, respectively, indicating that the LODs of MON810, Bt11, and P35S were lower than 10 copies, and the LOD of GA21 was lower than 25 copies of maize haploid genome. The current study demonstrated that the qualitative methods would be fit for the detection and identification of these GM maize events and the P35S segment.

In this article, we report a novel real-time PCR-based analytical method for quantitation of the GM maize event LY038. We designed LY038-specific and maize endogenous reference DNA-specific PCR amplifications. After confirming the specificity and linearity of the LY038-specific PCR amplification, we determined the conversion factor required to calculate the weight-based content of GM organism (GMO) in a multilaboratory evaluation. Finally, in order to validate the developed method, an interlaboratory collaborative trial according to the internationally harmonized guidelines was performed with blind DNA samples containing LY038 at the mixing levels of 0, 0.5, 1.0, 5.0 and 10.0%. The precision of the method was evaluated as the RSD of reproducibility (RSDR), and the values obtained were all less than 25%. The limit of quantitation of the method was judged to be 0.5% based on the definition of ISO 24276 guideline. The results from the collaborative trial suggested that the developed quantitative method would be suitable for practical testing of LY038 maize.

We have developed a real-time PCR array method to comprehensively detect genetically modified (GM) organisms. In the method, genomic DNA extracted from an agricultural product is analyzed using various qualitative real-time PCR assays on a 96-well PCR plate, targeting for individual GM events, recombinant DNA (r-DNA) segments, taxon-specific DNAs, and donor organisms of the respective r-DNAs. In this article, we report the single-laboratory validation of both DNA extraction methods and component PCR assays constituting the real-time PCR array. We selected some DNA extraction methods for specified plant matrixes, i.e., maize flour, soybean flour, and ground canola seeds, then evaluated the DNA quantity, DNA fragmentation, and PCR inhibition of the resultant DNA extracts. For the component PCR assays, we evaluated the specificity and LOD. All DNA extraction methods and component PCR assays satisfied the criteria set on the basis of previous reports.

To reduce the cost and time required to routinely perform the genetically modified organism (GMO) test, we developed a duplex quantitative real-time PCR method for a screening analysis simultaneously targeting an event-specific segment for GA21 and Cauliflower Mosaic Virus 35S promoter (P35S) segment [Oguchi et al., J. Food Hyg. Soc. Japan, 50, 117-125 (2009)]. To confirm the validity of the method, an interlaboratory collaborative study was conducted. In the collaborative study, conversion factors (Cfs), which are required to calculate the GMO amount (%), were first determined for two real-time PCR instruments, the ABI PRISM 7900HT and the ABI PRISM 7500. A blind test was then conducted. The limit of quantitation for both GA21 and P35S was estimated to be 0.5% or less. The trueness and precision were evaluated as the bias and reproducibility of the relative standard deviation (RSD(R)). The determined bias and RSD(R) were each less than 25%. We believe the developed method would be useful for the practical screening analysis of GM maize.

Real-time polymerase chain reaction (PCR)-based quantitative methods were previously developed and validated for genetically modified (GM) maize or soy. In this study, the quantification step of the validated methods was modified, and an interlaboratory study was conducted. The modification included the introduction of the PCR system SSIIb 3 instead of SSIIb 1 for the detection of the taxon-specific sequence of maize, as well as the adoption of colE1 as a carrier included in a reference plasmid solution as a replacement for salmon testis. The interlaboratory study was conducted with the ABI PRISM 7700 and consisted of 2 separate stages: (1) the measurement of conversion factor (Cf) value, which is the ratio of recombinant DNA (r-DNA) sequence to taxon-specific sequence in each genuine GM seed, and (2) the quantification of blind samples. Additionally, Cf values of other instruments, such as the ABI PRISM 7900 and the ABI PRISM 7000, were measured in a multilaboratory trial. After outlier laboratories were eliminated, the repeatability and reproducibility for 5.0 samples were

A novel type of quantitative competitive polymerase chain reaction (QC-PCR) system for the detection and quantification of the Roundup Ready soybean (RRS) was developed. This system was designed based on the advantage of a fully validated real-time PCR method used for the quantification of RRS in Japan. A plasmid was constructed as a competitor plasmid for the detection and quantification of genetically modified soy, RRS. The plasmid contained the construct-specific sequence of RRS and the taxon-specific sequence of lectin1 (Le1), and both had 21 bp oligonucleotide insertion in the sequences. The plasmid DNA was used as a reference molecule instead of ground seeds, which enabled us to precisely and stably adjust the copy number of targets. The present study demonstrated that the novel plasmid-based QC-PCR method could be a simple and feasible alternative to the real-time PCR method used for the quantification of genetically modified organism contents.

A real-time PCR detection method was developed for event-specific quantitation of Roundup Ready maize, GA21. The developed PCR method was designed to amplify an artificial junction site between the native maize genome DNA and the recombinant DNA of GA21 maize, which provides only one target sequence per haploid of GA21 genome. Thus, the amplification efficiency of the event-specific target for GA21 became closely similar to the amplification of SSIIb, and the conversion factor (Cf) for the quantitation method was similar to the theoretical value. The developed method demonstrated better performance than the existing construct-specific method that has been used as a Japanese official method. The developed method can easily be combined with the real-time PCR targeting of the CaMV35S promoter, and the multiplexed method should be an effective screening method for GM maize.

We developed a specific method to extract DNA from rice grain samples and modified the qualitative real-time PCR method provided by Bayer Co., Ltd. for reliable detection of the genetically modified (GM) rice variety, LLRice601, which has not undergone safety assessment for regulatory approval in Japan. Moreover, we conducted a data analysis to confirm the results obtained with real-time PCR. The yields of DNA extracted from powdered samples of rice grains were almost equal among 5 different varieties of rice, and there was no significant difference in the yield over three days. Reliable results were obtained using 50 ng of the extracted DNA as the template for real-time PCR. To examine the adequacy of the methods, we organized an interlaboratory study with the participation of 2 laboratories, in which 80 test samples were analyzed in a blinded manner. The statistical analysis revealed no significant difference in the Ct value for the endogenous gene of the DNA samples and for the targeted DNA sequence of 0.1% samples. The limit of detection of the method was approximately 0.1%. Analysis of the fluorescence intensity of the PCR-amplified product of the construct-specific DNA sequence suggested that it may be reasonable to judge a sample as positive when a Ct value of less than 40 is obtained.