Abstract: The ribosomal genes (45S rDNA) encoding ribosomal RNA synthesis were located in nuclear organizer region (NOR) in plants.The number of NOR should be corresponding to the number of chromosomes with satellite. The 45S rDNA was probed to the metaphase chromosomes and interphase nucleus from male and female Ginkgo plants using fluorescent in situ hybridization (FISH). The metaphase chromosomes and interphase nucleus of female plants displayed four hybridization signals while male plants displayed three signals, indicating that the female plants had four chromosomes with satellite while the male plants had three chromosomes with satellite only. The sex determination of Ginkgo plants was related likely with the number of chromosomes with satellite.

Key words: Ginkgo biloba L., Ribosomal gene, Sex determination, Fluorescent in situ hybridization