Analysis of the mechanism and induction of usefull somaclonal variations in plant breeding

1.在水稻愈伤组织再生体系的第二代中，部分后代分离出白化病、黄变、条纹病和白化病等突变体。这些突变基因可能属于细胞核基因组。在长期的培养中，获得了半矮秆、早抽穗的后代，这对水稻的育种具有重要意义。2.以欧洲烟草（Nicotiana sylvestris）愈伤组织为外植体，在含有欧洲烟草幼叶提取物的培养基上进行培养。在无叶提取物的培养基上培养的细胞染色体数目为2n=24的频率显著高于在无叶提取物的培养基上培养的细胞。3.利用根癌农杆菌介导法将潮霉素抗性基因（HYG^R）的GUS基因导入烟草愈伤组织。在根、茎和叶中观察到同源DNA序列重组恢复的GUS活性。4.在水稻中发现了与玉米MuDR转座子部分同源的基因组克隆。5.用紫外线（UV-B）照射大豆幼苗，通过RT-PCR方法扩增查尔酮合成酶基因家族的特异区域，发现所有基因家族都有RNA扩增，尤其是第5号基因。通过组织和细胞培养诱导抗UV-B植物的准备工作正在进行中。

1.In the second generation of regenerants derived from the calli of rice (Oryza sativa cv. Akihikari).some progenies segregated into several mutants such as albino, xantha, stripe and alboviridis. These mutant genes may belong to the nucleus genome. In the long term culture we obtained progenies with semidwarf and early heading which may be very important for the plant breeding of rice.2.The calli of Nicotiana sylvestris were cultured on the medium containing the young leaf extract of N.sylvestris. The frequency of cultured cells with normal chromosome number, 2n=24, were significantly higher than the cells cultured on the medium without the leaf extract.3.The GUS gene cut in the middle by hygromicin resistant gene (HYG^R) were transformed to the tobacco callus by using agrobacterium tumefaciens. The GUS activity recovered by the recombination of homologus DNA sequences was observed in root, stem and leaf. This indicates that the recombination occurs within a chromosome.4.The genomic clone which is partially homologus with the MuDR transposon of corn was found in the rice. This clone, however, did not recover the activity of transposable element in the cell culture of the rice.5.The seedlings of soybean were applied by the ultraviolet rays (UV-B) and then special regions of RNA (chalcone syntase gene family) were amplified by RT-PCR.The amplification of RNA was observed in all gene family, especially No.5 gene. Preparation for the development of UV-B resistant plant induced by tissue and cell culture is now on the way.