中文摘要：

【目的】沙田柚是中国特有的柚类名优品种,但种子多,一般100粒左右。为创新三倍体无核品种积累育种材料,本研究通过实生筛选获得不同倍性沙田柚新种质,同时运用基因组原位杂交（GISH）技术分析天然与人工四倍体新种质的染色体组组成。【方法】随机采集沙田柚自然授粉果实,萌发种子检测其染色体数目获得倍性变异植株;以2x母株gDNA为探针,同获得的4x植株中期染色体杂交进行GISH分析。【结果】从6000粒沙田柚种子中共获得三倍体5株,四倍体9株;对沙田柚天然与人工四倍体新种质的基因组原位杂交（GISH）分析表明,天然四倍体中有7株为异源四倍体,2株为同源四倍体,秋水仙碱诱导获得的人工四倍体4株均为同源四倍体;初步观察显示;与二倍体相比,四倍体植株生长缓慢,树冠较小,枝短而密生,叶片浓绿,宽度变宽,叶形指数减小,叶片厚度增加明显。【结论】多倍体单胚柚新种质的获得为进一步选育无核品种奠定了基础,同时GISH分析证实了沙田柚雌性未减数配子的存在。

英文摘要：

【Objective】Shatianyou （Citrus grandis Osbeck. cv. Shatianyou） is an elite pummelo cultivar in China,but it is seedy with about 100 seeds per fruit. The aim of this experiment was to obtain different ploidy new germplasm for seedless triploid breeding by screening seedlings,and to analyze genome constitution of natural and artificial tetraploids by genome in situ hybridization （GISH）.【Method】 Open-pollinated seeds were collected randomly,ploidy variation seedlings were screened by chromosome counting; In order to analyze genome constitution of tetraploids,the labeled total gDNA of diploid as probe was hybridized to tetraploid metaphase chromosomes by GISH. 【Result】Five triploids and nine tetraploids were found from 6 000 seeds. GISH analysis of tetraploids showed that there were seven allotetraploid and two autotetraploid in natural tetraploids,while four artificial tetraploids from colchicine induction were all autotetraploid. Preparatory morphology observation on different ploidy plants suggested that tetraploids grew slower than comparable diploids. Tetraploids have smaller tree crown ,shorter vernal branches,greener and obvious thicker leaves than corresponding diploids,but with smaller leaf indexes because of their bigger width. 【Conclusion】These monoembryonic polyploids are valuable for seedless breeding. GISH result has proved the existence of unreduced eggs in Citrus grandis cv. Shatianyou.