Jump to content
Powered by

International procedures for the detection and identification of GM seeds

Genetically modified seeds can have severe consequences. If even tiny amounts of adventitious GMO material are identified in a seed batch, it is not placed on the market. International procedures for sampling and testing seeds are therefore of huge importance for evaluating seeds traded on the international market. The Agricultural Technology Centre Augustenberg (LTZ) in Karlsruhe is accredited by the International Seed Testing Association (ISTA) to carry out seed analyses. It also carries out international cooperative studies on GM seed analyses in cooperation with ISTA.

ISTA draws up internationally agreed rules for seed sampling and testing, including methods for assessing the presence of genetically modified (GM) seeds. Cooperative studies are carried out to promote the uniform application of seed evaluation procedures worldwide and they also form the basis for ensuring that only quality seeds are traded on the international level. Between June 2010 and August 2013, six collaborative studies for standardising and improving the quality and efficiency of methods for detecting genetically modified organisms (GMO) in seeds were carried out. The studies were part of a cooperative project between LTZ Augustenberg and ISTA that was funded by the German Federal Office for Agriculture and Food.

No international test standards despite strict guidelines

“Seed investigations are carried out to ensure that the quality of the seeds in terms of GMO corresponds to the information provided by companies that commercialise the seeds and that no unwanted genetically modified plants are growing in crop fields,” says Dr. Andrea Jonitz, head of the Department of Seed Testing at LTZ Augustenberg. “This also ensures that the crop harvests are free from genetically modified seeds.” Jonitz also stated that although no large proportions of adventitious GM constituents have been discovered in non-GM seed lots, the fact that GM seed contaminations may result from harvest carryovers, processing or transport of plants cannot be excluded. 

European legislation defines the GM contamination threshold for seeds; irrespective of other EU regulations, the GM contamination threshold must not exceed 0.1%, which is the concentration that can be identified with state-of-the-art techniques. In addition, the OECD bans seed from being commercialised unless it has been thoroughly tested for the adventitious presence of GM seed according to ISTA criteria. However, this regulation only makes sense if standard methods for detection and identification of adventitious GM seeds are available. “Although several seed testing methods exist, no uniform international standards are yet available,” Jonitz explains. In addition to accredited seed testing laboratories having to demonstrate that they are technically competent to carry out seed testing procedures in accordance with the ISTA International Rules for Seed Testing, international cooperative studies are carried out to validate and harmonise GMO-specific testing methods.

Before LTZ carried out GMO studies in collaboration with ISTA, a decision had to be made on the type of genetic modification (so-called GMO events) to be examined. The GMO events were then mixed with GMO-free material to produce samples for investigation. ISTA was responsible for test design, selection of GMO events, announcing and organising the experiments and subsequent evaluation, LTZ is in charge of investigating, producing and dispatching the samples. 

LTZ Augustenberg: a pioneer in seed analytics

The photo shows a laboratory technician purifying the DNA required for the preliminary investigation of the seeds used in the studies. The purified DNA is then amplified and investigated for the presence of genetically modified DNA fragments. © LTZ Augstenberg

LTZ Augustenberg was entrusted with sample testing and preparation due to its long-standing experience in the development of analytical methods. Preventive consumer protection is one of the core areas of the Technology Centre, which comes under the auspices of the Baden-Württemberg Ministry of Rural Areas and Consumer Protection. 

LTZ has been carrying out GMO testing according to ISTA methods and rules since 2001. This makes it one of the first laboratories to be accredited by ISTA for specified trait testing including the detection, identification and quantification of GM seeds. “Only one other institute besides LTZ Augustenberg, the Thuringian State Institute of Agriculture in Jena, is accredited by ISTA to carry out GM seed testing procedures according to ISTA International Regulations for Seed Testing,” Jonitz says.

Six LTZ employees who work in the field of seed and feed testing and microbiology are involved in the cooperative studies. Before the studies began, the seeds were checked for the presence of GM material in non-GM seed lots using real-time PCR. DNA is extracted from the seeds and mixed with specific reagents (e.g. polymerase, nucleotides containing triphosphate groups, primers and fluorescent probes), placed in a thermal cycler (in this case a LightCycler LC 480 device) and amplified. The concentration of defined DNA sequences can be determined with the fluorescent probes used. This enables the identification of genetically modified DNA fragments and their concentration in the samples under investigation in real time. 

Following these initial experiments, reference seeds and GMO events were mixed; different samples containing different proportions of GMO events were prepared. “In addition to reference samples that did not contain any GMO events, each of the studies focussed on three to four samples that contained GMO events with a concentration range between 0.11 and 2%,” Jonitz said. Soybean, flax and maize seeds were used for the investigations and analysed by a total of 40 to 54 laboratories from Germany, the EU and other countries around the world. Each laboratory was in charge of analysing between eight and ten samples.

Results of the first three studies which were carried out with soybean (Glycine max), flax (Linum usitatissimum) and maize (Zea mays) seeds. The majority of laboratories produced error-free results as far as sample quality was concerned, but their quantitative results differed considerably.
Results of the first three studies which were carried out with soybean (Glycine max), flax (Linum usitatissimum) and maize (Zea mays) seeds. The majority of laboratories produced error-free results as far as sample quality was concerned, but their quantitative results differed considerably. © ISTA Secretariat, Zürich Bassersdorf, CH

High accuracy as far as seed quality is concerned

The results are analysed both qualitatively and quantitatively. The qualitative investigation of the samples involved correctly identifying the presence of genetically modified material in the samples; the quantitative investigation of the samples was designed to provide accurate information on the proportion of GMO events within a sample. So far, the results of three studies have been evaluated; between 87 and 94 percent of participating laboratories determined the presence of GMO events correctly. However, a much larger number of laboratories (up to two thirds) had problems in determining the quantity of GMO material present in the sample under investigation. The results will be used by ISTA as a basis for developing further testing methods, as well as serving as a basis for the debate on GMO threshold levels in Germany and OECD countries. These trials are of considerable importance as Germans have a somewhat critical attitude towards green genetic engineering.

Further information:
Dr. Andrea Jonitz
Head of the Department of Seed Testing and Applied Botany
Agricultural Technology Centre Augustenberg
Neßlerstraße 23-31
76227 Karlsruhe
Tel.: +49 (0)721/9468-150
Fax: +49 (0)721/9468-387
E-mail: Andrea.Jonitz(at)ltz.bwl.de

 

Website address: https://www.biooekonomie-bw.de/en/articles/news/international-procedures-for-the-detection-and-identification-of-gm-seeds