The effect of xylose on the callus growth of perennial ryegrass

Xylose as a selective agent is considered to be biosafe for plant genetic transformation. For investigating the possibility of xylose isomerase gene as a selective marker in genetic transformation of perennial ryegrass (Lolium perenne), the effect of xylose on the growth of calli which derived from mature embryos of perennial ryegrass was detected. Cultured on subcultivation medium （SM） with different proportions of sucrose, xylose and sucrose+xylose respectively，the calli were analyzed and their weight gain were determined after 5 week culture. The results of this study showed that the weight gain of calli increased with the enhancing of sugar content from 0 to 30 g/L. Calli grew much better on the media with sucrose than with xylose at the same concentration. At 30 g/L total amount of sugar in the mixed media, the weight gain of calli declined when the proportion of sucrose decreased in the meanwhile xylose increased. These results presented that xylose restricted the callus growth evidently. Moreover, on the media of SM+5 g/L sucrose+25 g/L xylose or SM+30 g/L xylose, the biomass increment was lower than others. It was suggested that xylose could be employed as a positive selective agent in perennial ryegrass genetic transformation at the selection pressure of 25 g/L xylose+5 g/L sucrose or 30 g/L xylose.