Molecular assessment of thermotherapy and meristem culture efficiency on some ‎virus’s eradication from important commercial pear cultivars (Pyrus communis L.)‎

This study was aimed to eradicate three viruses, Apple chlorotic leaf spot virus (ACLSV),Apple stem grooving virus (ASGV) and Apple stem pitting virus (ASPV) from seven pear cultivars including Abate Fetel, Beiruti, Dargazi, Coscia, Louise Bonne, Mellina, Spadona. Experiments were performed by evaluation of the effectiveness of thermotherapy duration including 0, 7, 14 and 21 days at 38 °C and meristem culturing in size of less than 0.2 mm on virus eradication rates of explants. At first mother samples were tested for ACLSV, ASGV and ASPV by and RT-PCR and all samples were infected by all three viruses, except Abate Fetel and Beiruti samples, that were free of ASP virus. Thermotherapy and meristem culturing were performed in vitro</em>. Explants from thermotherapy and meristem culturing were tested by RT-PCR for all three viruses and the results showed that eradication rates of ACLSV, ASGV and ASPV, respectively 78.46, 26.63 and 35.5 percent were different in the different pear cultivars. The highest rate of virus eradication was related to Coscia and the lowest to Spadona cultivars. There was a direct relationship between increasing the duration of thermotherapy and virus elimination of explants, but this increased period of time up to 21 days reduced the growth and multiplication and even destroyed the explants. Therefore, 14 days of thermotherapy was the most effective treatment for elimination of ASGV, ASPV and ACLSV, respectively 61.4, 100 and 45.5 percent, from pear explants. At the end of the experiment, samples that were diagnosed virus free using RT-PCR, were proliferated, rooted and transferred to greenhouse condition for acclimation stage.