FISH Analysis In Cabbage-Chinese Cabbage Allotriploid Hybrid And Chinese Cabbage Alien Addition Lines

Chinese cabbage (Brassica campestris L. ssp. pekinensis syn. rapa) and cabbage (Brassica oleracea var. capitata L.), belonging to the same genus Brassica, are both vegetables crops grown extensively in the world and important materials for studying the origination, evolution and relationship bewteen A and C genomes in Brassica. Furhermore, these valuable genetic materials such as alien addition lines between Chinese cabbage and cabbage are significant for gene mapping, special chromosome map construction and chromosome project breeding in Chinese cabbage and cabbage, which will be useful for genetic research and variety improvement.In this paper, we selected the genomic DNA of Chinese cabbage as probes. GISH technique were applied to study the distribution of chromosome hybrid signals at the mitosis metaphase. the space distribution of allotriploid chromosomes at the earlier prophase of meiosis, chromosome pairing configuration at diakinesis, chromosome arrangement at metaphase and chromosome separation behavior at anaphase of meiosis in cabbage-Chinese cabbage allotriploid hybrid. At the same time, cabbage-Chinese cabbage allotriploid hybrid and some Chinese cabbage-cabbage monosomic alien addition lines were analyzed by 25S rDNA-FISH technique.. The number and location of 25S rDNA-FISH signals at metaphase chromosomes of each materials were detected. The homologous between Chinese cabbage chromosomes with 25S rDNA locus and cabbage chromosomes were analyzed. For those monosomic alien addition lines with differences in chromosome number, the variation in chromosome number of root tip cells was investigated. The study results were as follows:1. The labeled genomic DNA of Chinese cabbage was hybridized to chromosomes of cabbage-Chinese cabbage allotriploid hybrid (ACC) at mitosis. When blocking DNA was not used in GISH, the hybridization signals were detected on 28 chromosomes of allotriploid and mainly distributed on proximal centromere and satellite region..2. At the earlier prophase of cabbage-Chinese cabbage allotriploid meiosis, the chromosome centromere regions of cabbage and Chinese cabbage were assembled to form several compacted chromosome groups with big or small size, around which the chromosome arms were imcopactly twisted and distributed. And the hybridization signals of Chinese cabbage genomic DNA were observed on these groups. 3. At the diakinesis of cabbage-Chinese cabbage allotriploid meiosis, chromosomes could form univalent, bivalents, trivalents and imitated multivalents. At metaphase I and II, the univalents were often distributed at the outside equator plate. At anaphase I and II, there were much abnormal phenomena such as chromosome lagging, chromosome bridge forming, and chromatids earlier separating; chromosome number varied from 10 to 19 at each pole.4. Nine 25S rDNA signals were detected in the cabbage-Chinese cabbage allotriploid hybrid. They were respectively located on the end of chromosome 5 and the satellite region of chromosome 9 in cabbage, the long-arm proximal centromere regions of chromosome1, 3, 4 and 5 in Chinese cabbage, and the satellite region of chromosome 2 in Chinese cabbage.5. Based on the FISH analysis at diakinesis of the allotriploid hybrid, one Chinese cabbage chromosome with 25S rDNA signal was homologous with cabbage chromosomes and formed one trivalent; two Chinese cabbage chromosomes with 25S rDNA signal were not homologous with cabbage chromosomes and formed two univalents, other two Chinese cabbage chromosomes with 25S rDNA signals were often related to one-to-three bivalents of cabbage and formed imitated multivalents.6. Eleven 25S rDNA signals were detected in Chinese cabbage-cabbage monosomic aline addition line 5, one of them was located on the short-arm terminal of alien chromosome 5 of cabbage. The alien chromosome was formed univalent at diakinesis and not aligned on the equatorial plate at methaphase I.7. Ten 25S rDNA signals were detected in one Chinese cabbage-cabbage monosomic alien addition line 5-3-9, which was not observed on the alien chromosome. According to karyotypic parameters, the line 5-3-9 was primarily suggested to be one monosomic alien addition line with cabbagechromosome 1.8. The extensive variation in chromosome number in root tip cells of three Chinese cabbage-cabbage monosomic alien addition lines with 21 chromosomes, 6-2-4, c-2-4 and d6, was obsevered after vegetative propagation multi-generations. The chromosome number varied from 17 to more than 50. The 25S rDNA signals were very complex in the three different clones.