Abstract:

The phylloclades as the experimental material of five cultivars of Schlumbergera truncata and Rhipsalidopsis gaertneri，Schlumbergera bridgesii，Nopalxochia ackermannii‘Evening Dress’，to identify the ploidy levels and to determine genome size and perform karyotype analysis. The results from flow cytometry indicated that the R. gaertneri，S. bridgesii，N. ackermannii‘Evening Dress’are all diploid. The chromosome numbers of R. gaertneri，S. bridgesii，and N. ackermannii‘Evening Dress’were all 22，and all had karyotypes of type 1A. The karyotype formulas and asymmetric coefficients were 2n = 2x = 22 = 18m + 4sm，57.64%；2n = 2x = 22 = 22m，57.93%；and 2n = 2x = 22 = 20m + 2sm，57.33%，respectively. Schlumbergera truncata cultivars‘Wanqiu’‘Fengguan’and‘White Double Flowers’are all diploid. The chromosome numbers were all 22，and karyotype formulas of 2n = 2x = 22 = 20m + 2sm，2n = 2x = 22 = 18m + 4sm and 2n = 2x = 22 = 20m + 2sm，respectively. The karyotype asymmetry coefficients were 56.53%，58.10% and 57.93%，belonging to types 1A，2A and 2B，respectively. The chromosome number of the triploid S. truncata‘R9’was 33，and a karyotype formula of 2n = 3x = 33 = 30m + 3sm，with an asymmetric coefficient of 58.57%，belonging to type 2A. The tetraploid S. truncata‘Guifei Zuijiu’had a chromosome number of 44，and a karyotype formula of 2n = 4x = 44 = 32m + 12sm，with an asymmetric coefficient of 60.24%，belonging to type 2A. The evolutionary trend analysis suggests that the evolutionary levels are ranked from high to low as follows：tetraploid，triploid，diploid. S. truncata can be hybridized with its diploid relatives，namely R. gaertneri，S. bridgesii and N. ackermannii‘Evening Dress’. The karyotype formulas of R. gaertneri and S. truncata‘Fengguan’are the same. The karyotype formulas of N. ackermannii‘Evening Dress’and S. truncata‘Wanqiu’are the same as those of S. truncata‘White Double Flower’，but the karyotype classification of‘White Double Flower’is different from the other two. The clustering results indicated that the eight materials were divided into two major groups. R. gaertneri，S. bridgesii，S. truncata‘Wanqiu’and N. ackermannii‘Evening Dress’clustered into group A，while the other four S. truncata cultivars clustered into group B. The distances between groups can more accurately reflect the phylogenetic relationships among the cultivars.

Key words: Schlumbergera truncata, Rhipsalidopsis gaertneri, Schlumbergera bridgesii, Nopalxochia ackermannii, chromosome, flow cytometry, ploidy, karyotype analysis