ABSTRACT
This chapter provides an overview, illustrated with relevant examples, of the main mechanisms used by the fl uorescent pseudomonas group to protect plants from pathogenic fungi. The biological control of fungal root pathogens can be achieved by a variety of mechanisms such as secretion of antibiotics and other antagonistic metabolites, niche occupation or exclusion and the induction of systemic resistance and other responses in the plant. It has been estimated that 10 percent of rhizobacteria possess biocontrol ability (Rezzonico et al. 2007). The genus Pseudomonas, together with bacteria belonging to the genera Bacillus and Streptomyces, constitute an important fraction of the total rhizospheric bacteria (Chin-A-Woeng et al. 2003) and their presence is associated with the suppression of diseases in soil (Haas and Defago 2005). Pseudomonas spp. can suppress a wide range of symptoms and diseases, for instance the damping-off caused by the oomycete Pythium
Department of Biology, Autonomous University of Madrid. *Corresponding author: maria.contreras@uam.es
ultimum and the basidiomycete Rhizoctonia solani affecting sugar beet and radish; selected examples of activity against other pathogenic fungi are presented in Table 12.1.
