Comparative screening of bacteria for biological control of potato late blight (strain US-8), using in-vitro, detached-leaves, and whole-plant testing systems

Forty-three bacteria were isolated from the phylloplane and (or) rhizosphere of potato and canola plants and tested for their ability to control the pathogen Phytophthora infestans (strain US-8) causing late blight on potato. This study revealed the benefit of using more than one system when searching for biocontrol activity. In this regard, the complementarity of the three systems chosen (in-vitro culture media, detached leaves, and whole plants) in selecting and identifying potential modes of action, provided a useful insight into the different types of biocontrol activity present. Bacteria with biocontrol activity were from the genera Bacillus, Pseudomonas, Rahnella, and Serratia. Mechanisms of inhibition characterized included those occurring directly, through antibiosis, and (or) indirectly, through the induction of plant defense systems.