Comparing the efficiency of conventional and novel methods of virus elimination using molecular techniques

Viral pathogens significantly affect pear growth and reduce annual production across the world. This study aimed to examine whether conventional virus elimination methods, including thermotherapy (0, 7, 14 and 21 d at 38 °C), meristem culture (less than 0.2 mm, between 0.2 to 0.7 mm and larger than 0.7 mm) and adventitious shoot regeneration from leaf explants can lead to virus-free pear seedlings when compared to chemotherapy (sodium nitroprusside (SNP); 0, 10, 17, 25, 50 and 70 μM). Five pear cultivars (“Abate Fetel”, “Beiruti”, “Dargazi”, “Coscia” and “Louise Bonne”) were investigated to check if those treatments are capable of eliminating three key viruses in pear, namely Apple chlorotic leaf spot virus (ACLSV), Apple stem pitting virus (ASPV) and Apple stem grooving virus (ASGV). The plant’s infection to the viruses was examined using reverse transcription polymerase chain reaction (RT-PCR), followed by applying the treatments, meristem culture and in vitro cultivation. Results surprisingly showed a direct relationship between an increase in duration of thermotherapy and virus elimination. Moreover, it was shown that small size of the cultivated meristem increased the rate of virus elimination, even though the responses were different in terms of the cultivars and viruses. Shoot regeneration had very low efficiency in leaf explants as it could only eliminate ASPV from pear explants. Interestingly, the experiment demonstrated that nitric oxide treatments were more effective in virus elimination than the other treatments. A year later, samples that were diagnosed virus-free were proliferated, rooted and transferred into pots to be used for later propagation and establishment of a mother orchard.