Chapter 7 - Phytopathogenic fungi and their biocontrol applications

Abstract

Phytopathology is the scientific study of diseases in plants caused by pathogens (infectious organisms) and environmental conditions (physiological factors). Fungi are among the dominant causal agents of plant diseases. With respect to plant pathogens, fungi represent probably the most diverse group of ecologically and economically important threats. Most phytopathogenic fungi belong to the Ascomycetes and the Basidiomycetes. Phytopathogenic fungi use various strategies to colonize in plants and cause disease. Phytopathogenic fungi possess a wide range of enzymes destroying the carbohydrate polymers, which constitute the building materials of the cell walls. Some fungi kill their hosts and feed on dead material (necrotrophs), while others colonize the living tissue (biotrophs). For successful invasion of plant organs, pathogenic fungi developed strongly regulated and specialized infection structures. To further colonize hosts and establish disease, fungal pathogens organize a plethora of virulence factors and these interactions result in a broad spectrum of outcomes reaching from beneficial interactions to death of the host. Depending on the infection strategy, virulence factors perform different functions. While basically all pathogens interfere with primary plant defense, necrotrophs secrete toxins to kill plant tissue. In contrast, biotrophs utilize effector molecules to suppress plant cell death and manipulate plant metabolism in favor of the pathogen. Biological control of plant diseases with fungal pathogens has been considered a sustainable alternative method comparison to other chemical control. In plant pathology, the term biocontrol applies to the use of microbial antagonists to destroy diseases. Throughout their lifecycle, plants and pathogens interact with a wide variety of organisms. These interactions can expressively affect plant health in several ways. Different mode of actions of biocontrol-active microorganisms in controlling fungal plant diseases include soil amendments, hyperparasitism, entomogenous fungi, predation, antibiosis, cross protection, competition for site and nutrient and induced resistance. Successful application of biological control strategies requires more knowledge-intensive management. Commercial use and application of biological disease control have been slow mostly due to their variable performances under diverse environmental conditions in the field. To overcome this problem and in order to take the biocontrol technology to the field and expand the commercialization of biocontrol, it is important to develop new formulations of biocontrol microorganisms with higher degree of stability and survival. Future outlooks of biocontrol of plant diseases is bright and promising and with the growing demand for biocontrol products among the growers, mass production of biocontrol microorganisms and the use of biotechnology and nano-technology in improvement of biocontrol mechanisms, manage plant diseases, increase yield, protect the environment and biological resources and approach a sustainable agricultural.