Karyotypes and Giemsa C-banding patterns of Zebrina pendula, Z-purpusii and Setcreasea purpurea, compared with those of Tradescantia ohiensis

It has been proposed that the genera Zebrina and Setcreasea of the family C ommelinaceae should be united and reunited, respectively, with the genus Tr adescantia, mainly based on morphological studies. In the present study, ka ryotypes and Giemsa C-banding patterns in the root-tip cells of three Zebri na and two Setcreasea clones were analyzed, and were compared with those of a triploid Tradescantia clone. Z. pendula and Z. purpusii (both 2n = 24) w ere found to have similar karyotypes (4 M + 6 ST + 14 T; M = meta-, ST = su btelo-, T = telocentric chromosomes), while Z. pendula cv Quadricolor (2n = 23) had a unique karyotype (6 M + 5 ST + 11 T + 1 SA; SA = short acrocentr ic chromosome). The only clear difference between Z. pendula and Z. purpusi i was that one and two subtelocentric chromosomes, respectively, had satell ites at the short arms. Two clones of S. purpurea (2n = 24) had karyotypes (8 M + 8 M' + 8 SM; M' = nearly meta-, SM = submetacentric chromosomes) sim ilar to each other. T ohiensis (2n = 18) had a symmetric karyotype (9 M + 9 SM) consisting of larger chromosomes than S. purpurea. Many clear Giemsa C -bands were detected, in addition to centromeric bands in all chromosomes o f all clones. Z. pendula and Z. purpusii commonly had single clear intersti tial bands in eight telocentric chromosomes each, but they also had unique telomeric and other interstitial bands, respectively. Z. pendula ev Quadric olor had a unique banding pattern, i.e., satellite bands in the unique shor t chromosome, telomeric bands at the long arms of all metacentric chromosom es, and single interstitial bands in six telocentric chromosomes. Two clone s of S. purpurea had telomeric bands at many chromosome arms and satellite bands in two nearly metacentric and one submetacentric chromosomes, but som e differences were found between them. On the other hand, all the chromosom es of T ohiensis had telomeric bands at both arms, and three submetacentric chromosomes had satellite bands. These result prove structural differentia tion of chromosomes occurred among the clones, especially in Zebrina, and s how that S. purpurea is relatively close to T ohiensis, while Zebrina is ob viously distant from the other two genera. Therefore, there remains a quest ion cytologically at least for uniting Zebrina with Tradescantia.