Identification of domestic rice cultivars by RAPD method using a single grain of cooked rice as a sample

Precooked rice dishes, box lunch and "Onigiri", cooked rice ball have been increasing in the market these days. As it is obligated that the cultivar of the material rice grains of these products should be displayed without mislabeling, the development of the objective detection method is indispensable. Therefore, RAPD method to identify the cultivars of the cooked rice grains were investigated. Milled rice grains were cooked in the plastic microtubes, followed by the enzymatic digestions using alpha-amylase for starch and proteinase-K for proteins. DNAs were extracted by phenol solution and purified by ethylalcohol. The DNAs were proliferated by the PCR method with the existence of various kind of primers (10 mers and 12 mers). The resultant electrophoregram showed that the dominant 10 Japanese rice cultivars could be identified by the combination of 6 selected primers and suitable DNA bands. It became possible to identify the rice cultivar using a single grain of cooked rice by the enzymatic digestion of starch and proteins followed by the application of RAPD method.