八倍体小黑麦耐盐细胞系产生的遗传机制

GENETIC MECHANISM OF THE OCCURRENCE OF SALTTOLERANT VARIANT OF OCTOPLOID TRITICALE UNDER TISSUE AND CELL CULTURE 

实验选用来源于八倍体小黑麦（×ＴｒｉｔｉｃｏｓｅｃａｌｅＷｉｔｍａｃｋ）杂种一代Ｂ、Ｃ和原种Ｆ三个品系的成对单倍体和双倍体细胞系，在１％、１．５％和２％ＮａＣｌ水平进行耐盐变异体筛选及其发生机制研究。实验和分析结果表明，未经筛选的细胞系由三类细胞组成，第一类是占大多数没有任何适盐性的细胞，第二类是具有一定适盐性的非变异体细胞，可在继代筛选中被淘汰，第三类细胞是变异体细胞；第二类细胞在杂种材料细胞系中所占比例少于原种细胞系，故杂种细胞较易筛选到耐盐变异体；比较三个级别筛选的变异体频率发现，后一级筛选的变异必须以前一级筛选的变异为基础，即耐盐变异体发生的遗传机制是基因扩增；双倍体细胞中正常同源染色体对基因扩增变异的表达有干扰作用，这种干扰因材料不同在各级筛选中呈现不稳定状态。

Three pairs of haploid and diploid cell lines, respectively originating from three octoploid triticale lines, F 1 hybrids B and C and primary strain F, were used for in vitro selection of salt tolerant variants at 1.0%, 1.5% and 2.0% NaCl levels, for the purpose of studying the genetic mechanism of the occurrence of salt tolerant variant. Experimental and analytical results showed that non selected cell lines consisted of three classes of cells. The first class cells which accounted for the majority of a cell line had no salt adaptability, the second class cells were non variant cells with some salt adaptability, that could be gradually eliminated through subcultures on selection medium. The third class were variant cells. The percentage of the second class cells in the hybrid derived cell lines was less than that of the cell lines from homozygous primary strain, thus it was relatively easy to select the salt tolerant variants from the hybrid derived cell lines. In comparing the variant frequencies of the three rounds of selections it was found that the variation in second round selection was based on the variation accurred in the first round selection, and by comparing the characteristics of these variants it was proposed that a genetic mechanism played in the production of salt tolerant variant cell could be an amplification of the salt tolerance genes with dominant effectiveness. The normal homologous chromosome in the diploid cell could interfere with the expression of the salt tolerant variation resulted from gene amplification. Such interference varied with the different genetic background of the triticale lines and appeared inconsistent among different rounds of selections.