| The wild germplasm of rugosa rose from four distributions in China and 25 rugosa rose cultivars were taken as the experimental materials in this paper. The conventional stem-tips squashed method was improved and the somatic-cell-chromosomes of rugosa rose were studied. Through identification of chromosome numbers, analysis of karyotypes and exploration of effective approach of karyotype analysis of rugosa roses, the aim of this paper was to provide the basic data of rugosa roses and fill the blank in the area of chromosome study of rugosa roses. The main study results were as follows:1. According to existing plant cytological achievements, the study methods of chromosome was improved and a set of simple, economical and efficient karyotype analysis method was explored.The new shoots were collected in clear days of autumn in 9:00-11:00 AM and 14:00-16:00 PM. The young leaves should be divested. Tender tissues were pretreated with saturated 1,4dichlorobenzene solution or 0.002mol/L 8-Hydroxy quinoline for 2-3h, fixed in freshly prepared Carnoy's fixed liquid (1:2 acetic- alcohol) for 2-24h., hydrolyzed in the mixed solution (HCL: 95%alcohol=1:1) for 10 min at room temperature and stained with improved fuchsin solution. Squashing, microscopic examination and measurement were then carried on. The pairing and arrangements of chromosomes were made using Adobe photoshop.2. The karyotypes of Chinese wild rugosa rose and main rugosa rose cultivars were studied systematicly and some useful conclusions were drawn.The actural length of chromosomes of Rosa rugosa varied from 1μm to 4μm, belonging to small chromosomes. The wild germplasm and majority of cultivated germplasm were diploid and had 2n=2x=14 except R. rugosa'Canxueyingxia',R. rugosa'Yellow Swan',R. rugosa'Warm Red',R. rugosa'Suyu'which were polyploidy. The main components of karyotype were submetacentric chromosomes and metacentric chromosomes. The ratio of the longest chromosome and the shortest chromosome was less than 2. There were no chromosomes of the arm ratio more than 2. They were all belonged to 1A type which possessed higher symmetry.There were two karyotypic formula of wild germplasm:2n=2x=14m and 2n=2x=8m+6sm(SAT), seven karyotypic formula of cultivation germplasm: 2n=2x=14m, 2n=2x=14m(SAT), 2n=2x=12m+2sm, 2n=2x=12m+2sm(SAT), 2n=2x=11m+3sm, 2n=2x=10m+4sm and 2n=2x=8m+6sm.As to relative length, the main member of karyotype was M chromosome in wild and cultivation germplasm. A pair of S and L chromosomes respectively were contained at most.The varation of main arm length and asymmetric coefficient ranged 1.38~1.56% and 57.95~60.50% in wild germplasm, 1.27~1.61,55.51~61.62% in cultivation germplasm.3. According to the karyotype analysis of R. rugosa'Purple Branch', the cytological reasons of morphological variations were made clear. One of the fourth pair of chromosomes was metacentric and the other was submetacentric. The heterozygosity of part of homologous chromosomes was inner cause to varion in morphology.4. Four non-rugosa-rose-cultivars were identified and corrected for the first time.For a long time, R. rugosa'Canxueyingxia', R. rugosa'Yellow Swan', R. rugosa'Warm Red'and R. rugosa'Suyu'were regarded as rugosa rose cultivars. Compared with wild rugosa rose and other Rosa rugosa cultivars, the four cultivars were quite different not only in the chromosome numbers but in the external morphology. So we could prove definitely that the four cultivars were not belonged to Rose rugosa. Their scientific names should be corrected as R.'Canxueyingxia', R.'Yellow Swan', R.'Warm Red'and R.'Suyu'.5. The origination and evolution of rugosa rose in China were preliminarily deduced. The trend of karyotypic evolution in wild rugosa rose agreed with Stebbins theory, from symmetry to asymmetry. The intensity sequence of karyotypic asymmetry was R. rugosa in Rongcheng of Shandong >R. rugosa in Zhuanghe of Liaoning>R. rugosa in Hunchun of Jilin>R. rugosa in Muping of Shandong. R. rugosa in Muping of Shandong was in a primitive position while R. rugosa in Rongcheng of Shandong was in a comparatively evolutive position. We deduce that R. rugosa in China might be originated in Muping of Shandong province, then dispersed and evolved from south to north of China. R. rugosa in Rongcheng of Shandong Province which was near to that of Muping of Shandong in geographical position. This phenomenon need furthermore studied by other achievements.6. The relationships between karyotypes and phenotypes were discussed.Cultivated roses bring with different flower types and flower colours. From the view of karyotype, the chromosome numbers of rugosa rose cultivars were the same and the karyotypes had little differences. Character variations may not be reflected at karyotypic level. That was to say, there were no correlations between flower types & colours and karyotypes.
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