ABSTRACT
The biotic biological control agents (BCAs) have been isolated from soils, plants and water bodies, using appropriate growth media. Polymerase chain reaction-based molecular techniques have been more frequently used to identify, differentiate and quantify the BCAs in different substrates. The interactions between microbial plant pathogens and the biological control agents (BCAs) may vary and they may be differentiated into mutualism, antagonism, parasitism, competition and predation. The dual culture method, a preliminary test, is followed to select fungi with antagonistic activity against the target microbial pathogen(s). Bacterial species existing in various substrates such as seeds, propagules, plants, soil and water have been shown to possess antagonistic properties against soilborne microbial plant pathogens, resulting in suppression of disease development. Nonpathogenic isolates or strains of fungal and bacterial pathogens are known to protect plants against infection of virulent strains of the pathogens.
