Abstract:A moderately repetitive DNA sequence from rice ( Oryza sativa L. ) has been cloned by the method of DNA renaturation kinetics. Different restriction enzymes digestion and Southern hybridization indicated that this sequence was organized in tandem array and dispersed in rice genome. There was a perfect plant promoter element TGTATAAATA within the sequence. Copy number of the cloned repetitive DNA sequence pRRD3 was determined within 34 varieties of Oryza, detectable differences were found between wild rice and cultivated rice as well as subspecies indica and japonica. Southern blot analysis on different AA genome type rice DNA showed genome subtype-specific hybridization pattern, suggesting that the repetitive DNA sequence pRRD3 is a useful probe to study the evolution and classification of rice.