PHYSICAL MAPPING OF THE 5S RDNA GENE-COMPLEX IN RICE (ORYZA-SATIVA)

This study was designed to use biotin labelling in situ hybridization to physically map the 5S rDNA genes to a chromosome arm location in ri ce. Chromosome preparations were made using an improved protoplast tec hnique, which resulted in more mitotic cells with less overlying cytop lasmic and cellular debris. Cells in which both chromatids were labell ed were observed. The hybridization detection level for the 5S rDNA ge ne complex was 17.22%. The results established that the 5S rDNA gene c omplex of rice is located at the end of the short arm of chromosome 9 in rice cultivar IR36. The similarities and differences of the 5S rDNA gene complex location between rice and other cereals and advantages o f in situ hybridization for physical mapping are discussed.