Abstract:The karyotype and fluorescent banding of chromosomes from root tips of Citrus grandis ‘Shatianyou’ seedling were analyzed by CMA/DAPI double staining to investigate the chromosomal structure of ‘Shatianyou’.Results showed that there were six different CMA banding patterns:A type was a chromosome with two terminal and one proximal bands; B was a chromosome with one terminal and one proximal band; C was a chromosome with two terminal bands; D,a chromosome with one terminal band; E,a chromosome with one small terminal band only; F,a chromosome without any bands.CMA banding pattern formula of most seedlings was 2n=18=3A+1B+2C+4D+8F,whereas some were 2n=18=3A+1B+2C+4D+4E+4F,2n=18=3A+1B+2C+4D+8E,2n=18=2A+2B+2C+4D+8F or 2n=18=2A+2B+2C+4D+4E+4F.Compared with CMA bands,DAPI bands were opposite patterns and there were some weak DAPI signals in different degrees.Somatic chromosome synapsis and 2-4 fragile sites were also observed.