Isolation, characterization of nematode-controlling bacteria and fungi from nature

Abstract

The root-knot nematodes (genus Meloidogyne) are a major endoparasitic pest affecting the production of many economically valuable annual and perennial crops worldwide in tropical and subtropical climatic zones. The infected plants show typical symptoms which include root galling, lack of vigor, stunting growth, nutrient deficiency particularly nitrogen deficiency, yellowing of leaves, and wilting under water stress conditions. The root-knot nematodes are one of the most destructive and difficult diseases to control in agricultural sector. These nematodes cause billions of US dollars in yield loss annually every year. The use of chemical nematicides is usually effective and has been used for over 50 years, but they cause significant environmental pollution as most nematicides are highly toxic compounds. Among the various strategies advocated to manage root-knot disease is the use of native biocontrol agents as an integral component of integrated disease management. The use of biocontrol agents from bacteria and fungi has been the focus of many researchers, mostly for development of microbial biopesticides against diseases and pests. The efforts have resulted in several microbial insecticides being marketed in many countries. A comprehensive understanding of mechanisms of disease inhibition by bacterial or fungal pathogens remains limited. In this chapter, we investigated the uses of some biocontrol agents to control root-knot nematodes if not totally eliminate them from our agricultural fields. The results showed that certain groups of bacteria and pathogenic fungi have been intensively studied, and some were developed for use as microbial bioinsecticides. The success of these bioinsecticides relies mainly on the activities of the fungus and bacteria, which can be affected by various environmental factors along with the interaction between the pathogen and its host insect pest.