Fast and Effective Thermotherapy Treatment for In Vitro Virus Eradication in Apple and Pear Trees

Abstract

Heat therapy followed by the isolation and in vitro culture of apical meristems is a suitable procedure for virus eradication. However, the period of heat treatment is usually long (28 - 50 days) and the yield of viable plants free of viruses after treatment is often low (<50%). Here, we describe an alternative method to obtain virus-free plants. We used traditional Galician cultivars, six apple trees and two pear trees, infected with Apple chlorotic leaf spot virus (ACLSV) and Apple mosaic virus (ApMV). We combined heat therapy of in vitro shoots using a temperature gradient from 25˚C to 40˚C increasing 1˚C per day for a shorter period of time (18 days) with the posterior isolation and culture of apical meristems. All DNA samples analyzed, obtained from plants developed from meristems, were 100% free of ApMV and almost 90% free of ACLSV. With this in vitro procedure combined we obtained a good yield of tested plants free of viruses...