A review of the methodology to detect and identify Karnal bunt—a serious biosecurity threat

Tilletia indica , the cause of Karnal bunt of wheat, replaces part of the seed with a black powdery mass containing millions of spores and produces a strong unpleasant odour like rotten fish. The fishy smell has serious consequences for the marketability of wheat. The fungus is thus subjected to very strict quarantine regulations in countries not known to have the pathogen. The pathogen is spread through natural or human dissemination of spores. Research had shown that a detectable level of the disease would indicate the pre-existence of the pathogen for several years. Once present, this pathogen is extremely difficult to eradicate. Early detection at the incursion stage is thus very important to prevent disease establishment and the spread of the pathogen in a new area. Early detection in the field is unlikely. The key to its detection is thus the deployment of strategic surveillance and quarantine regulations in the wheat supply chain with the use of very sensitive and accurate diagnostic tools to detect and identify a small number of spores. This paper reviews the development of diagnostic assays of increasing sensitivity and specificity for the identification and differentiation of T. indica and other Tilletia spp. contaminants commonly found in wheat grains.