摘要：In recent years, Japan's yield of Koshihikari, the rice variety most prized by consumers, has increased year by year. However, it has been suggested that other varieties of rice are being mixed in with rice labeled and circulated as Koshihikari. The Japanese Agricultural Standards has therefore been revised and labeling based on the so-called Standards for Quality Labelling of Unpolished and Polished Rice introduced. The General Food Policy Bureau has carried out on-the-spot inspections to endure fair labeling and has published the results. To ensure fair labeling, it is additionally necessary to identify scientifically the rice variety. In the present study, in order to distiguish Koshihikari, we examined suitable methods of DNA extraction from rice grains and identified the varieties available on the market by PCR using STS-primers. Sufficient rice-grain DNA was extracted using a modification of the Wizard DNA Clean-up System method. 0.5-5.2mg of DNA was extracted from each rice grain. In the case of rice consisting of Koshihikari only, the validity of the labeling could be judged by PCR using an STS-primer. With some rice varieties, it was also possible to judge the validity of the labeling by comparing the PCR electrophoresis pattern with that of pure breeds. DNA of a rice variety other than indicated on the lavel was detected in about 40% of samples. The rate of contamination is however unknown. During rice cleaning, it seems likely that bran from other rice varieties adheres to the rice surface.
关键词：rice variety;PCR;Koshihikari;labelling of rice
