Detection of seed borne pathogens in wheat: Recent trends

Infected wheat seeds are the carrier of pathogens for long-distance dissemination. Major impact of seed borne diseases in wheat is not only the yield reduction but also deteriorate marketable quality of grains. Early detection of pathogens is a crucial step in diagnosis and management programmes in wheat. The failure to adequately identify and detect plant pathogens using conventional, culture based morphological techniques has led to the development of nucleic acid-based molecular approaches. Polymerase chain reaction (PCR) revolutionised pathogen detection and identification, but these methods have not yet entirely replaced traditional cultural and phenotypic tests practiced for detection of major wheat seed borne pathogens e.g. NaOH seed soak method for detection of Tilletia indica causing Karnal bunt of wheat. Methods for detection of seed borne microorganisms in wheat are ranged from simple visual observation to spectroscopic and imaging techniques. Immuno-diagnostic tools can also be successfully employed for differential diagnosis, disease surveillance of seed borne pathogens of quarantine importance and determination of teliospore load in wheat seeds. PCR-based methods result in high level of sensitivity, specificity is used for species-specific detection of Tilletia spp and Fusarium spp. The present paper highlights the brief outlines of traditional detection methods and discusses recent PCR-based and spectroscopic and imaging techniques being employed in detection of seed borne pathogens in wheat.