natural-products-in-plant-pest-management

248 M. Santos et al.Antibiotic production by strains of the bacteria Pseudomonas and Bacillushas been shown to be important to the successful biocontrol of several cropdiseases. The antibiotics zwittermicin A and kanosamine, produced by thebiocontrol agent Bacillus cereus UW85, appear to be important in the biocontrolof oomycetes such as Phytophthora (Silo-Suh et al., 1994; Milner et al.,1996). The antibiotic phenazine derivatives, produced by Pseudomonas fluorescensstrain 2-79 and P. aureofaciens strain 30-48, control take-all of wheat(Weller and Cook, 1983; Brisbane and Rovira, 1988).Trichoderma and Gliocladium are closely related fungal biocontrol agents.Each one produces antimicrobial compounds and suppresses disease bydiverse mechanisms, including the production of the structurally complexantibiotics gliovirin and gliotoxin (Howell et al., 1993). Mutants withincreased or decreased antibiotic production show a corresponding effect onbiocontrol (Howell and Stipanovic, 1983; Handelsman and Stabb, 1996).HyperparasitismHyperparasitism is parasitism on another parasite. The mycelium andresting spores (oospores), hyphae or sclerotia of several pathogenic soilfungi such as Pythium, Phytophthora, Verticillium, Rhizoctonia, Sclerotinia andBotrytis (Fig. 12.1) are invaded and parasitized (mycoparasitism) or are lysed(mycolysis) by several non-pathogenic microbes.Fig. 12.1. Microscopic photography (¥ 400) of Trichoderma saturnisporum catching Botrytiscinerea.