BIOCONTROL OF BACTERIAL PATHOGENS OF KIWIFRUIT PLANTS

Natural substances (animal and plant extracts) were tested in vitro and in vivo to verify their antimicrobial activity against phytopathogenic bacteria (Pseudomonas syringae pv. actinidiae, Pseudomonas syringae pv. syringae and Pseudomonas viridiflava) on kiwifruit at different concentrations (10⁴, 10⁵, 10⁶, 10⁷, 10⁸ colony forming units [cfu]/ml). Spot and well in vitro tests were carried out. All natural substances tested showed antibacterial activity inhibiting the growth of P. s. pv. actinidiae, P. s. pv. syringae, and P. viridiflava when the pathogen concentration was 104 cfu/ml, and some were also effective at higher pathogen concentrations (105–108 cfu/ml). In preliminary in vivo tests, natural substances gave interesting results for the control of bacterial pathogens, maintaining their populations below 104 cfu/cm2 in the kiwifruit phyllosphere for 15 days. Furthermore, these natural substances showed antimicrobial activity against both bacterial pathogens (P. s. pv. syringae and P. viridiflava) that cause parenchymatous damage and P. s. pv. actinidiae which causes vascular damage to kiwifruit plants. Biocontrol field experiments are in progress to confirm the results of these tests and to develop innovative strategies to control bacterial pathogens of kiwifruit.