Interlaboratory Validation of an Event-Specific Real Time Polymerase Chain Reaction Detection Method for Genetically Modified DAS59132 Maize

Abstract

A real-time polymerase chain reaction (PCR) method specific for genetically modified (GM) maize event DAS59132 (E32) was adapted for qualitative detection of low level presence of E32. The method was validated by a collaborative trial with eight participating Japanese laboratories. Sensitivity was assessed with three di#erent samples of corn flour fortified to 0῍, 0.05῍ and 0.1῍ (w/w) E32 respectively. In addition, a 0.01῍ E32 DNA solution was used. The detection limit with DNA solution was estimated to be approximately 0.01῍. In conclusion, the results of the study confirmed this real-time PCR method as a reliable tool for qualitative detection of E32 maize.Key words: genetically modified maize; recombinant DNA; real time PCR; detection method; DAS59132 IntroductionMany types of genetically modified organisms (GMOs) have been introduced over the past decade or so, and the number of commercially available bioengineered or genetically modified (GM) crops is increasing rapidly 1) . GM crops and their products have been authorized for food and/or feed use by many countries based on their respective criteria for safety assessment. In the European Union for example, the authorization and use of GM food and feed is governed by regulations (EC) No. 1829/2003 and (EC) No. 1830/2003 2), 3) . Japan implemented a mandatory safety assessment of GM foods and processed foods containing GM ingredients. Since April 1, 2001, any GM food that has not been authorized is prohibited from import or sale in Japan. Therefore, Japan requires detection methods for regulated and unauthorized GM crops and products. Previously, we reported the development of qualitative detection methods for GM products unauthorized in Japan, such as certain GM maize lines, GM potatoes (NewLeaf Plus, NewLeaf Y), GM papayas (Line 55-1 or its derivatives) and GM rice lines ('LibertyLink' rice and Chinese Bt rice lines) 4)ῌ17) ῌ In 2008, Dow AgroSciences LLC has voluntarily retrieved from US channels of distribution certain hybrid corn seed potentially containing adventitious, low levels of a regulated biotechnology maize event, DAS59132, also referred to as event 32 or E32. Dow AgroSciences LLC. advised and cooperated with U.S. regulatory authorities in this matter. The situation creates no human, animal or environmental safety concerns, because the Bt proteins produced in the E32 maize are identical to those found in biotech hybrid maize sold commercially and deemed safe. However, under Japanese, Korean and EU regulations the E32 maize is unauthorized and the potential low level presence of E32 could require monitoring before import.In the present study, we describe the results of an inter-laboratory study of an event-specific real-time PCR method to identify E32 maize. The experiments were conducted at eight laboratories in Japan. Materials and Methods Maize (zea mays) materialsCoarsely milled samples of E32 maize seed and non-GM maize seed were kindly provided by Dow AgroSciences LLC. Preparation of the test samplesThe E32 maize seeds and non-GM maize see...

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