Optimization of chromosome preparation and karyotype analysis of yellow-flower Chinese kale
Chinese kale (Brassica alboglabra Bailey) is an original Chinese vegetable belonging to the Brassicaceae family of cruciferae. It is commonly grown for its bolting stems and tender rosette leaves as the edible parts, which are tender and crisp. Chinese kale contains large amounts of health-promoting...
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| Main Authors: | , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Zhejiang University Press
2016-09-01
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| Series: | 浙江大学学报. 农业与生命科学版 |
| Subjects: | |
| Online Access: | https://www.academax.com/doi/10.3785/j.issn.1008-9209.2015.06.061 |
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| Summary: | Chinese kale (Brassica alboglabra Bailey) is an original Chinese vegetable belonging to the Brassicaceae family of cruciferae. It is commonly grown for its bolting stems and tender rosette leaves as the edible parts, which are tender and crisp. Chinese kale contains large amounts of health-promoting compounds, such as vitamin C, carotenoids, total phenolics, and glucosinolates. It is widely distributed in Guangdong, Fujian and Guangxi Provinces.The typical yellow-flower Chinese kale cultivar “Fuzhou-Huanghua” was used as the plant material, the chromosome staining factors, including sampling time point, pretreatment and dissociation duration, were optimized. Karyotype characteristics were also investigated, and then the obtained results were compared with those from the reported white-flower Chinese kale so as to reveal the karyotype differences.The seeds of “Fuzhou-Huanghua” were soaked for 2 hours, and then cultured in dark in petri dishes with moist filter paper at 25℃ for 3 days. The root tips were excised between 8:00-10:00 AM, with 30 min intervals to determine the optimum sampling time point; pretreatment in 0.002 mol/L 8-hydroxyquinoline were conducted for 1-10 h (1, 2.5, 5, 7.5 and 10 h, respectively), subsequently, the root tips were macerated in 1 mol/L hydrochloric acid at 60℃ for 1-16 min (1, 4, 8, 12 and 16 min, respectively). Thirty cells with clear metaphase chromosomes were selected, and then the numbers and karyotype analysis of chromosomes were done by the cytological standards.The results showed that the percentage of the mitotic cells and metaphase cells reached maximum when sampled at 9:00 AM; the best contraction, shape and dispersion of chromosomes were found at 5-h pretreatment with 0.002 mol/L 8-hydroxyquinoline; the best cell dispersion, chromosome staining and cytoplasm transparency, as well as the highest contrast ratio were observed at 8-min dissociation. Yellow-flower Chinese kale has a total of 18 chromosomes. The chromosome types included large chromosomes (L), middle chromosomes 2 (M<sub>2</sub>), middle chromosomes 1 (M<sub>1</sub>), and the constitution of the relative length was 2L+2M<sub>2</sub>+14M<sub>1</sub>. The centromeric index ranged from 27.86% to 48.19%, and the arm ratio ranked from 1.08 to 2.59. There were four pairs (the first, forth, sixth and ninth chromosome) of submetacentric chromosomes (sm) and five pairs (number two, three, five, seven and eight chromosome) of metacentric chromosomes (m), while the two satellites (SAT) were observed at the sixth pair of chromosomes. The karyotype formula was 2n=2x=18=10m+8sm (2SAT). Karyotype asymmetry index (As. K) was 61.95%, and karyotype characteristics fell into type 2A according to STEBBINS classification criteria. Meanwhile, significant differences in karyotype formula, ratio of chromosome length (L/S), and range of chromosome relative length were observed when comparing the chromosome characteristics between yellow-flower and the reported white-flower Chinese kale. Specifically, compared with the above results, four m and five sm chromosomes were reported in six white-flower cultivars. Moreover, the ratio of chromosome length (L/S) in yellow-flower Chinese kale (1.48) was lower than that in white-flower Chinese kale cultivars (1.50-1.71), which is mainly due to the fact that the shortest chromosome relative length in yellow-flower Chinese kale (9.66%) was obviously higher than that in white-flower ones. However, no significant difference was observed in arm ratio range, As. K or satellite position between the two types.In conclusion, the optimized chromosome preparation conditions and karyotype analysis of yellow-flower Chinese kale were revealed. These results will enrich the awareness of genetic composition of Chinese kale, and provide cytological evidence for the study on the taxonomic status and phylogenetic relationship of these taxa. |
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| ISSN: | 1008-9209 2097-5155 |