IJUP08 - Universidade do Porto

Detection of genetically modified soybean in foodstuffs:
Participation in an inter-laboratorial study
M. Carvalho 1 , I. Mafra 1 , J. Rocha 1,2 , M.B.P.P. Oliveira 1
1 REQUIMTE-Laboratory of Bromatology, Faculty of Pharmacy, University of Porto, Portugal.
2 Faculty of Sciences, University of Porto, Portugal.
In last ten years, the agriculture has been revolutionized by the introduction of genetically
modified organisms (GMO). The soybean is one of the most important genetically
modified crops, totalizing 83.8 milions of planted hectares, which correspond to 57% of
biotechnological planted area [1].The acceptance of GMO by consumers is controversial,
and concerns about their safety persist among public opinion. The EU legislations demand
the labelling of food products containing more than 0.9 % of GM material (Regulation
(EC) N.º 1829/2003).
The interest of USDA/GIPSA Proficiency Program is to perform accurate, reliable, and
reproducible testing on biotechnology-derived events. The objective of this Program is to
detect and quantify GM maize and soybean flours by means of DNA and/or protein based
methods to verify the performance of several laboratories of individual organizations.
The aim of the present work was the detection of GM soybean of three ground soybean
samples supplied by the Proficiency Program in two periods. The samples were received
with the information of one specific GM event ranging from 0 to 5%. The most accepted
techniques for GMO detection rely on DNA based methods, namely polymerase chain
reaction (PCR) or real-time quantitative PCR techniques due to their high specificity and
sensitivity. Thus, the PCR techniques were the choice for the present study. The isolation
of DNA from soybean flours was carried by using two methods: the CTAB and the Wizard
[2]. Yield and purity of DNA extracts were assessed by spectrophotometry, while
amplifiability was evaluated by PCR targeting the lectin gene. Two types of PCR assays
were developed and used: convetional PCR assays for detection of Roundup Ready (RR)
soybean and real-time PCR assays for quantitative purposes. The results received by the
first period of the Program showed good performance of the Laboratory of Bromotology to
screen GMO by targeting the 35S promoter and by the qualitative detection of RR
soybean. Concerning the second period of the Program, the results of the three samples
analysed by real-time PCR with TaqMan probes were: 0.8%, 2.5% and 0.2% of GMO. The
report for the second period is not yet available to conclude about the performance of the
present work.
References:
[1] James, C. (2006), Global Status of Commercialized Biotech/GM Crops:2006, ISSAA Brief No.
35, New York, Ithaca: ISSAA.
[2] Mafra, I., Silva, S.A., Moreira, E.J.M.O., Ferreira da Silva, C.S., Oliveira, M.B.P.P.
Comparative study of DNA extraction methods for soybean derived food products, Food Control
(submitted).
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