In vitro cultures of Actinidia deliciosa (A. Chev) C.F. Liang & A.R. Ferguson: a tool to study the SAR induction of chitosan treatment.

Kiwifruit (Actinidia deliciosa (A. Chev.) C.F. Liang & A.R. Ferguson), a profitable crop with a steady growth in export, should be certainly preserved from the most common diseases. Kiwi plants were strengthened with a natural compound, the chitosan, a well-known elicitor of Systemic Acquired Resistance (SAR), to study and evaluate the interaction between this compound and in vitro cultures, in order to propose a possible alternative to reduce the number of chemical pesticide treatments in the prevention of disease outbreak. To detect the effectiveness in eliciting SAR, the effects 15 and 50 mg/L of chitosan on kiwi micropropagated plants were tested at the in vitro multiplication stage. Different biochemical markers were measured, like phenols and several enzymes involved in defence response, i.e. guaiacol-peroxidase (G-POD), ascorbate peroxidase (APX), phenylalanine ammonia lyase (PAL) and polyphenol oxidase (PPO). The beneficial growth effect was also evaluated measuring the dry biomass and the total soluble protein content of treated plants. The systemic disease protection elicited by chitosan has been detected thanks to its ability to enhance the activity of enzymes involved in detoxification processes (G-POD and APX) and in increasing plant defence barriers (PAL and PPO). In addition, chitosan treatment increased both dry biomass and protein contents demonstrating a general enhancement of plant fitness.