Molecular detection of fungal pathogens and induction of phytoimmunity using bioinoculants

Abstract

The present review deals with the serological and molecular techniques available for detection of fungal pathogens in plants, followed by management practices using bioinoculants which can induce resistance in the hosts. Specific detection of pathogens in the plant tissues even before the appearance of symptoms are done either through protein based immunodiagnostic techniques or DNA/RNA based molecular techniques. Immunotechniques depend on specific interaction between antigen of the pathogen or infected tissues and antibodies prepared against the specific antigen. Positive reactions are detected through either qualitative or quantitative techniques. Among the immunodiagnostic techniques, the most widely and commonly used is the enzyme linked immunosorbent assay (ELISA), Dot blot, Western blot and Immunofluorescence. The molecular techniques are predominantly PCR based and include different variations with increasing sensitivity such as nested PCR, multiplex PCR, reverse transcriptase PCR, real time PCR, loop-mediated isothermal amplification (LAMP) and nano based PCR. Thus, by use of one or more sophisticated techniques it is possible to detect pathogens rapidly and specifically. Pathogen detection is generally followed by management techniques, and in the current scenario ecologically safe bioinoculants are used for induction of immunity in the plants. There are several bioinoculants based on beneficial microorganisms such as plant growth promoting bacteria, biocontrol agents and arbuscular mycorrhizal fungi. Application of these microorganisms, singly or as a consortium, has been reported to induce immunity in plants. Induced systemic resistance (ISR) operates through signal molecules and pathways involving jasmonate and ethylene, and in very few cases, salicylate. Upregulation of these pathways leading to enhanced accumulation of antimicrobial compounds (phytoalexin) help in warding off the pathogen during subsequent attack.