Abstract
Many strains of Plant Growth Promoting Rhizobacteria (PGPR) have the ability to induce the systemic resistance in several pathosystems. This study investigates the protective effect of four strains belonging to Bacillus subtilis (Bs168, Bs2500, Bs2504 and Bs2508) on grapevine roots of the sensitive local grapevine cultivar “Helwani” against phylloxera. Fresh roots were immersed in bacterial suspensions 0, 3, 5 and 15 hours before infesting with phylloxera eggs. Results of biometric measurements showed significant differences in the life cycle of phylloxera between treated and untreated roots. Bacillus strains negatively affected phylloxera development and reproduction. The efficiency of treatment increased when root immersion time in the bacterial suspension increased. On the other hand, there were significant differences between strains in terms of their protective effect against phylloxera, but Bs2508 strain was the most effective especially when the roots were immersed for 15 hours. This study supports previous studies in order to employing PGPR strains as biocontrol agents against pests.