79 tube-plants of 30 improved citrus varietes were regenerated by thermothera-py and shoot-tip grafting during 1989~1992 in Hunan province,18 of them belonging to 10varietes,detected with plant indicator,electronic microscope and two-way polyacrylamide gelelectrophoresis,have proved to be free of CEV,CTLV,CTV and Hunang Luingbin,23 ofthem belonging to 10 varieties have been primarily detected and the results show that theyare free of aforementioned diseases.20 parent varieties from Hunan province and other areashave been detected with electron...