Cryopreservation of Virus-infected Pear Shoot Tips by Vitrification and Plant Regeneration

Effect of the time for pre-culture,PVS2 treatment and cryopreservation on regeneration rate of pear shoot tips infected with virus was studied.Results showed that the shoot tips(1.5~2.5 mm) pre-cultured in pre-culture medium(MS+2 mol·L-1glycerol +0.4 mol·L-1 sucrose+ 0.7% agar) for two days,then treated with 60% PVS2 at room temperature for 20 minutes,followed by dehydration with 100% PVS2 at 0 ℃ for 2 hours,at last,immersed directly in liquid nitrogen.After 24 hours,the shoot tips were post-cultured on regeneration medium(MS+6-BA 1.0 mg·L-1 +NAA 0.2 mg·L-1+3%sucrose+0.7% agar).The culture was maintained in the dark for three to eight days,then transferred to light conditions for survival and regrowth.The highest survival of shoot tips was 71%.The morphology of the plantlets regenerated from cryo-treated shoot tips was similar to that of control shoot tips.