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

1.在水稻愈伤组织诱导的第二代再生植株中。一些后代分离成几个突变体，如白化、黄化、条纹和白化。这些突变基因可能属于核基因组。在长期的培养中，我们获得了半矮化和早熟的后代，这可能对水稻的植物育种非常重要。2.将烟草的愈伤组织培养在含有野烟幼叶提取物的培养基上。染色体数目正常的细胞频率(2n=24)显著高于不含叶提取物的培养细胞。3.将潮霉素抗性基因(HYG、R)中间切下的GUS基因转化烟草愈伤组织。在根、茎和叶中观察到通过同源DNA序列重组而恢复的GUS活性。这表明重组发生在一个染色体内。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，RT-PCR扩增出查尔酮合成酶基因家族中特定区域的RNA(查尔酮合成酶基因家族)，并在所有基因家族中都观察到了RNA的扩增，尤其是5号基因。利用组织和细胞培养方法培育抗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.