Abstract: The xylem sap was collected from the stems of regular cotton (Gossyposium cv.‘Shiyuan321’) and Bt cotton (Gossyposium cv. ‘99B’ and ‘SGK321’), The soluble proteins and Bttoxin transportation were analyzed by Coomassie brilliant blue staining and ELISA, respectively.Bt insecticidal crystal protein existed only in Bt-cotton xylem sap, and the content of soluble proteins in xylem sap of Bt-cotton was remarkably higher than that of regular cotton. Grafting showed that Bt toxin could be conveyed to regular cotton leaves from transgenic cotton stock via xylem sap. Bt toxin distributed in plant tissue through xylem transportation is advantageous in terms of cotton resistance to worms.

Key words: Bt-cotton, Bt toxin, Xylem sap, Grafting