Abstract:Inactivation of mesophyll protoplasts from potato cultivars and its wild species was achieved by treatment with acridin orange(AO), under dark culture for 2 days and then exposure to light for 4h. The extent of this inactivation depent on the duration of AO treatment, the AO concentrations and the occasion for light treatment. The inactivation concentrations of tetroploid were higher than those of diploid. Immediate exposure to light after AO treatment showed strongest inactivation effect. Culture exposed to light after 8 days showed almost the same division pattern as control AO-treated in the dark. Small calli formed after fusion of protoplasts in rhodamine (P6G) inactivated potato (Solanum tuberosum) and AO-treated Solanum bulbocastanum.