• Antibiosis: Some beneficial organisms can produce antibiotics or other substances that are toxic to the pathogenic organisms. For example, bacteria Pseudomonas fluorescens strain CHAO produces hydrogen cyanide, 2,4‐diacetylphloroglucinol, and pyoluteorin, which directly interfere with growth of various pathogens. Other bacteria including Bacillus, Serrantia and fungi such as Thrichoderma and Gliocladium can produce antimicrobial compounds effective against plant root pathogens (Handelsman, 1996, Haas & Defago 2005, Weltzien 1991)).