Identification Of Partial Individual Chromosomes In Gossypium Raimondii And Gossypium Mustelinum

Fluorescence in situ hybridization with bacterial artificial chromosome (BAC) clone as probe, is areliable cytological technique for chromosome identification. In this study, we identified partialchromosomes of G. raimondii and G. mustelinum using BAC-FISH，which provided the foundation forthe cytogenetic research of the two species and had great significance for studying the donor ofallotetraploid and chromosomal structural reorganization in cotton. The main results were as follows:1．Positive clones was got by screening the BAC library of G. barbadense L. acc. Pima90-53usingselected SSR markers from chromosome1,2and10of tetraploid cotton genetic map. Positive BACclone and45S ribosomal DNA clone were hybridized to mitotic metaphase chromosomes of Gossypiumraimondii using dual-probes FISH. We finally got distinct hybridization signal specific to chromosomeD501, D502and D510, respectively. The three BAC clones389K13、384I04and280G06serves ascytological markers which can identify chromosome D501, D502and D510. All of the three BAC cloneswere located accurately in the long arm of chromosome D501, D502and D510using the D genomecentromere-specific BAC150D24probe.2. The three BAC clones were from BAC library of G. barbadense. So combined with BACsspecific to chromosome01,02and10of G. barbadense, the distribution of the three specific BACclones in G. barbadense were discussed using dual-BACs FISH. Results showed that three BAC clones389K13,384I04and280G06also were specific to chromosome Db01, Db02and Db10of G. barbadense.Compared with the position of the BACs specific to Db01, Db02and Db10of G. barbadense, the threeBACs all were located closer to the end of the chromosome. Comparing the distribution of the threeBACs in G. raimondii with in G. barbadense, we found that BAC clone280G06was separately locatedin the long arm of chromosome D510in G. raimondii and in the short arm of chromosome Db10in G.barbadense, so the position of BAC clone280G06in two species showed non-collinear. However, thelocation of the remaining two BACs in two species showed collinear.3. A set of chromosomes Am01-Am13in G. mustelinum were identified by BAC-FISH usingthirteen BAC clones specific to chromosome Ah01-Ah13of G. hirsutum. There were twelve BACclones which produced one specific signal in G. mustelinum except the BAC clone specific tochromosome Ah11. It produced two pairs of signals on the chromosomes of G. mustelinum, whichshowed there were homologous fragment in the two chromosomes. The existence of homologousfragment may be involved in chromosomal rearrangement, transposon, whole genome duplication etc.4. The number of rDNA loci of G.raimondii was determined by rDNA-FISH. There were threepairs of45S rDNA loci and one pair of5S rDNA in G.raimondii. On the basis of identifying individualchromosome, one of three pairs of45S rDNA was located in chromosome D502. We inferred thatG.raimondii was not D subgenome donor of tetraploid according to the position of rDNA loci in thesetwo species.5．There were three pairs of45S rDNA loci and two pairs of5S rDNA in G. mustelinum on thebasis of individual chromosome assignment. Three pairs of45S rDNA loci were located in chromosomeAm07, Am08, Am09, respectively. One of three pairs of45S rDNA loci was located within the short arm of chromosome Am08, maybe translocation or inversion was occurred during evolution of G.mustelinum. The45S rDNA loci in the end of chromosome Am08presented two tandem signals, so weassume that the45S rDNA loci in chromosome Dm09transferred to chromosome Am09throughunequal crossover, biased gene conversion or transposon, and the original45S rDNA loci inchromosome Dm09was deleted during evolution.