Abstract: In the present study, the green-stalk leaf beet cultivar was used as plant material, chromosome staining factors including dissociation duration, pretreatment and sampling time point were optimized, and karyotype characteristics were also investigated. The results showed that the best chromosome staining and cytoplasm transparency as well as the highest contrast were observed at 12 min dissociation; The best contraction, shape and dispersion of chromosomes were found at 9 h pretreatment with 0.002 mol·L^-1 8-hydroxyquinoline; The percentage of the mitotic cells and metaphase cells reached maximum when sampled at 9:00 A.M.. Leaf beet had a total of 18 chromosomes. The karyotype formula was 2n=2x=18=16m+2sm (2SAT), the ratio of chromosome length (L/S) was 1.52, and the constitution of the relative length was 8M₂+10M₁. The relative lengths ranged from 8.75% to 13.29%, the centromeric index ranged from 36.67% to 47.04%, and arm ratio ranked from 1.13 to 1.73. Moreover, the second pair of chromosomes, which own two satellites (SAT), was submetacentric chromosomes (sm), while other eight pairs of them were metacentric chromosomes (m). Karyotype asymmetry index (As.K) was 58.50%, and karyotype characteristics fell into type 1A according to Stebbins classification criteria. Meanwhile, the obtained results were compared with those from the already reported sugar beet so as to reveal the karyotype differences between the two, and the significant differences were found on karyotype formula, karyotype characteristics, satellites and As.K. In conclusion, the results revealed the karyotype characteristic of leaf beet, and provided a theoretical basis for karyotype comparison among different types of leaf beet.

Key words: leaf beet, chromosome, preparation optimization, karyotype analysis