Abstract:Three pairs of haploid and diploid cell lines, respectively originating from three octoploid triticale lines, F1 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% NaC1 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-vari-ant 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.