In vitro chemotherapy-based - based methods for virus elimination from Actinidia macrosperma

Viral diseases are widespread in all kiwifruit-producing areas around the world and negatively affect yield and fruit quality, severely limiting the sustainable production of kiwifruit. The availability of reliable methods for clean-up of stock plant materials is crucial to successfully manage viral diseases. In this study, we investigated whether meristem culture (Mc), thermotherapy (T), cryotherapy (Cryo) methods alone or in combinations with chemotherapy (R) could effectively eradicate Actinidia virus A (AcVA), Actinidia virus B (AcVB), and Actinidia chlorotic ringspot-associated virus (AcCRaV) from in vitro-cultured Actinidia macrosperma C. F. Liang. The effects of chemotherapy, thermotherapy, and their combinations on the vegetative growth of A. macrosperma in vitro were also evaluated. Virus-free plants were obtained from regenerated shoots after all virus eradication treatments except Cryo, which failed to eliminate AcCRaV. Chemotherapy and thermotherapy, applied alone or in combination, prior to meristem culture or cryotherapy, improved the virus eradication frequency. Moreover, ribavirin treatment, regardless of its concentration, had no negative effects on vegetative growth of A. macrosperma in vitro cultures. The highest virus elimination frequency was obtained in R25 (25 mg L-1 ribavirin) + T + Cryo, producing 44.4 % of virus-free plants, followed by R25 + T + Mc, which obtained 36.7 % of virus-free regenerated shoots. Our results indicate that chemotherapy-based methods are effective in eradicating kiwifruit viruses in mixed infections. The protocols described here, most of which have been evaluated for the first time in kiwifruit, have great potential to assist in the production and supply of healthy planting material for the kiwifruit industry.