Variation Of Chromosome Number And Physical Mapping Of RDNA On Metaphase Chromosomes In Eulaliopsis Binata

Eulalioposis binata is a tetraploid apomictic plant in Graminea. Embryological investigation indicates that the developmental pattern of embryo sac formation in Eulalioposis binata represents gametophytic apospory and the mode of embryo and endosperm development was autonomous. The degree of apomixes was over 95% in some populations of Eulalioposis binata. Therefore the sexual populations or plants were the basis for study the genetic regulation of apomixes. While there some evidence indicated that low ploidy plants were sexual in some apomictic species. In this paper, chromosome counting and ploidy study was conducted on 12 populations of Eulaliopsis binata for seeking different ploidy plants, especially low ploidy populations. At the same time, we explored the pre-treat time and temperature in the Squash Technique of root tip to determine the best pre-treat condition. We also studied the physical mapping of 45S rDNA and 5S rDNA on metaphase chromosomes in Eulaliopsis binata. The results are as follow:1 The pre-treatment was improved in the Squash Technique of root tip on Eulaliopsis binata. In this study, the root tips were treated by p-dichlorobenzene with different temperature and time. The chromosomes dispersed well while root tips were soaked in a saturated solution of p-dichlorobenzene at 4℃for 8 h.Through many experiments, this improvement achieved good effects.2 More than 30 root tips in each population of Eulaliopsis binata were observed separately, and more than 5 cells with dispersive metaphase chromosme were counted in each root tip. Results showed that most chromosomes numbers of these 12 populations were 40, which were tetraploid. But there were some variation of chromosome number in these population. For example, we observed 3 root tips have 20 chromosomes in Xi xia population. while,4 root tips were 30 chromosomes in Yuxian. But there was no difference in ploidy between populations, while Variation of chromosome number were found in some plants.3 FISH analysis on metaphase chromosomes of Eulaliopsis binata with DIG-labeled 45S rDNA and 5S rDNA probe was performed. There were four 45S rDNA loci, which were located on the near centromere region and satellite. The size and intensity of 45S rDNA hybridization signals was inconsistent, which means that the copy number of 45S rDNA is different. One 5S rDNA locus on metaphase chromosomes was observed, which located on the near centromere region. There was also one 5S rDNA hybridization signal on the interphase nuclei.