Karyotyping Of Brassica Napus And Brassica Oleracea Based On C_ot-1 DNA And RDNA Fluorescence In Situ Hybridization

To explore an effective and reliable karyotyping method in Brassica crop plants, Cot-1 DNA was isolated from Brassica napus L.(Zhongyou 821) and Brassica oleracea L. (Heiyexiaopingtou) genomic DNA.The Cot-1 DNA labeled with biotin in situ hybridized to their own mitotic spreads,and combined with rDNA labeled with DIG in B.oleracea.By the single-colour fluorescence in situ hybridization of B.napus C₀t-1 bands are located on the long arms of chromosome pairs 1,5,7,9 and 11,on the short arms of chromosome pairs 4,6,8,10,12,15,17,18 and 19,and on the pericentromeric sites of chromosome pairs 2,3,13,14,and 16.By the dual-colour fluorescence in situ hybridization of B.oleracea the Cot-1 DNA were located on the long arms of chromosome pair 3 and 9,the short arms of chromosome pair 4,5,7 and 8,and the pericentromeric sites of chromosome pair 1,2 and 6;the 25S rDNA were located on the short arms of chromosome pair 4 and 7,and the signals on the chromosome pair 4 were stronger;and the 5S rDNA were located on the only chromosome pair and the signals were poorer.On the base of the chromosome length and arm ratios the karyotype formula of B.oleracea was established as 2n=2x=18=18m+2sm,and the karyotype was 2B.The specific and steady fluorescence signal bands of Cot-1 DNA in situ hybridization(FISH) were detected on all their individual chromosome pairs.Two members of each homologous chromosome pair were the same and non-homologous chromosomes had different banding patterns.The sites existing the Cot-1 DNA hybridization signals existed the rDNA signals,and chromosome sites identity between Cot-1 DNA and 25S rDNA was determined.Based on the length and location of the Cot-1 DNA and rDNA hybridization bands together with length and arm ratio of chromosomes,the karyotype of B.oleracea were more effectively constructed,and their idiograms on the dual-FISH were described.All these showed that the karyotyping technique based on a combination of rDNA and Cot-1 DNA chromosome landmarks was superior to alone one,and much superior to the karyotyping method on the chromosome morphologies.It would conduce to the plant karyotyping and the physical map construction.