A karyological study of 22 Rosa taxa,including 5 wild species,8 old garden roses and 9 modern cultivars,was performed using traditional squashing and pressing methods.There are three ploidy levels among the taxa,R.multiflora var.cathayensis is triploid with 21 chromosomes(2n=3x=21),the other wild taxa are diploid with 14 chromosomes(2n=2x=14),and the modern rose taxa are all tetraploid with 28 chromosomes(2n=4x=28),while the old garden roses contain all three ploidies.Four karyotypes(1A,2A,1B and 2B) have been found among the taxa,with 1A and 2A in wild species,1A,2A and 1B in old garden roses,and 1A,1B and 2B in modern roses.Also,the studied taxa differ from each other in the asymmetry index,centromere index,satellite position and number and constitution of relative lengths.The results indicate that karyological diversity is abundant in Rosa germplasm resources.