Acceleratedin vitrothermotherapy and indexing against apple chlorotic leaf spot virus in Shiro plum

Virus and virus-like diseases are major production constraints in vegetatively propagated crops; once a plant is infected, it remains so throughout its life. This work was undertaken to accelerate the process of eliminating apple chlorotic leaf spot virus (ACLSV) from explants obtained from an infected plum tree by in vitro heat therapy combined with meristem tip culture. After a minimum of 1 week of in vitro heat treatment followed by microdissection of meristematic tissues, trees were propagated successfully into virus-free plants. The treatment procedure, from infected plant to virus-free plantlets, takes a minimum of 14 weeks and could be applied to other fruit tree crops. The results of a one-step reverse transcription PCR analysis of treated plants after three accelerated growth cycles indicated the absence of ACLSV. Heat treatment of the test plants, followed by three rounds of indexing, was accomplished in about 28 months, a procedure that could take ≥36 months using conventional methods. The techniques described in this work may help to speed up the treatment of infected plants and screening of planting materials. The application of these procedures will benefit regulatory agencies, allow stakeholders to have timely access to virus-tested material, and facilitate domestic and international trade.