Study On Elimination Of Latent Viruses In Vitro-cultured Plants Of Sand Pear(Pryrus Prfolia) By Thermotherapy And Shoot-tip Culture

Apple chlortotic leaf spot virus (ACLSV),apple stem grooving virus (ASGV) and apple stem pitting virus (ASPV) are three latent viruses in pome fruit trees,which are distributed worldwide. About 86.3% of main pear tree varieties in China are infected by the three latent viruses.Based on viral disease infection by grafting techniques on pear for these virus,the major efficient way of mitigating them is via the planting of virus-free germplasm.In this study,with the in vitro sand pears infected three latent viruses was used as source for viral materials.Heat treatment under 34℃/40℃combined shoot tip culture were used as techniques for virus elimination.Branches were collected from 21 varieties sand pear plants and virus detection was done by RT-PCR.Detections showed that all the materials collected contain at least one of three latent viruses. The infected rate was as follow:90.48% ACLSV,85.71% ASGV and 42.86%ASPV.For the 21 varieties containing 251 buds,shoot tip culture was done in a proliferative MS (MS+0.2 mg/L, IBA+1.0 mg/L 6-BA, Agar 5.4 g/L, sucrose 30 g/L, pH5.8),366 in vitro plants of 20 cultivars were obtained.Result showed that survival rate and differentiation coefficient varied between cultivars. The highest survival rate of 100% was reached for Anlongyihao, Qingxiang, Guiguan and Fengshui,the lowest of 0% reached of Jingshuiyihao. For tip differentiation coefficient, Zhongliyihao was the highest followed by Xingao.Guiguan and Cuiguan recorded the lowest becquse they show no tip polarization.15 cultivars of in vitro sand pear have been dectected,including 79 buds.Results showed that the detection rate of ACLSV was 67.09%(53/79), the detection rate of ASGV was 86.08%(68/79), the detection of ASPV was 32.91%(26/69).8 varicties of sand pear were treated under 34℃/4℃(8h/16h alteration) coupled with shoot tips culture,for1014 buds.For the same cultivars 69 strains processing materials were obtained. It resulted that cultivars'survival rate and multiplication coefficient were different.The survival rate was 14.7%,9% and 2.11% or Zhongliyihao Qingxiang and Jingqiu and Huangjing.The proliferation coefficient of Yuanhuang was 2.7,that of Xinggao was 2; Aiganshui,Fengshui and Huangjing were not appear proliferation.8 pear cultivars of 65 regenerated plans were detected by RT-PCR.Results showed that 5 sand pear clutivars were obtained,including 39 in vitro plants.The virus eliminate rate of different cultivars were different.The eliminate rate of ACLSV stands at 90.77%, that of ASGV at 70.77%,and 95.38% for ASPV.