Studies On Molecular Cytogenetics Of Three Sorghum Species

In this study,the genetic relationship of S. bicolor, S. dochna and S. propinquum and the prediction of the heterosis F1 hybrids between S. bicolor (♀)×S. propinquum(♂),S. dochna (♀)×S. propinquum(♂)were analyzed by polyacrylamide gel eletrophoresis(PAGE) method.The metaphase and prometaphase chromosome maps of S. bicolor ,S. dochna and S. propinquum were constructed by DAPI stained.The 45S rDNA loci was physically mapped onto the chromosomes of S. bicolor ,S. dochna and S. propinquum and their F1 hybrids .The genomics evolution between S. bicolor ,S. dochna and S. propinquum were analyzed.The main results are as follows:1. Applying of polyacrylamide gel eletrophoresis(PAGE) method,the isozyme patterns of peroxidase(POD),esterase (EST),superoxi dedismutas(SOD),polyphenol oxidas(PPO) of F1 hybrids between S. bicolor×S. propinquum,S. dochna×S. propinquum and their parents were analyzed.The results indicated that POD,EST,PPO zymagram type of S. bicolor and S. dochna were similar,but different from S. propinquum ,we can concluded that the genetic relationship of S.bicolor and S.dochna were closed,but distandly with S. propinquum.nevertheless,SOD could not distinguish S.bicolor,S.dochna with S. propinquum,because they hadn't a special isozyme band.In their F1 hybrids the POD , EST zymograms of all F1 hybrids and the SOD,PPO zymograms of two species in F1 hybrids were similar or the same as to male parent, and had complementary bands POD-1,EST-3,PPO-1 for parents and new heterodimeric band POD-4,while did not express POD-6 which was common for parents.Therefore,the research results could provide reference to breed new hybrid materials.2. DAPI chromosome binding is a new developing molecular cytogenetic technique in recent years.It is under taken by ananlyzing the intensely and faintly stained regions or bands on chromosomes after fluorescence stain.Accracy of chromosomal identification could be notably improved.Based on the DAPI staining patterns,with chromosomal relative length and arm ratio as supplementary paramenters,the metaphase and premetaphase chromosome maps were constructed in S. bicolor ,S. dochna and S. propinquum.3. Phsical location of 45S rDNA loci was examined in genus sorghum of S. bicolor ,S. dochna and S. propinquum by FISH.The positions of 45S rDNA loci showed as knob or condensation regions in the interphase nucleus of these species,distributional of two signals signals were distended on premetaphase chromosomes.Each 45S rDNA loci occurred at two sits on the short arm of chromosome 1,near the centromer,where the secondary constrition is in metaphase chromosomes. The perecnt distances from centromere to detection sites were 58.6%,35.9%,37.8%.4. With the help of fluorescence in situ hybridization (FISH),we have located and analyzed the sites of the 45S rDNA loci on the F1 hybrids of S. bicolor×S. propinquum,S. dochna×S. propinquum. The two signals of 45S rDNA loci were mapped on the mitotic metaphase chromosomes in the F1 hybrids respectively, and a signal show on a bivalent during meiotic of synaptene,diakinesis and metaphase I. We inffered that the two mitotic chromosomes which took 45S rDNA loci were homologous pairs. Considering the signals of 45S rDNA loci location during meiotic process, the material of these two F1 hybrids exhibited normal action, the average of configurations were the same as below : 2n=2x=20(10Ⅱ)。Our results indicated that 45S rDNA loci could provide a landmark for identification individual chromosome during meiotic process indirectly.5. The comparative analysis of genomic evolution between closely or distantly related species has been analyzed by a genomic DNA cross-hybridized with other species. S. propinquum genomic DNA has been used as a probe cross-hybridized with S. bicolor ,S. dochna ,the results revealed highly homoeologous in repeat sequence and conserved genome evolution.In conclusion,innovative results of this study is that the availability of 45S rDNA locu to positions on mitotic and meiotic chromosomes of hybridizeds by FISH, the chromosomal action and the genomic evolutional relationship among genera of sorghum has been analyzed at the level of molecular.