An enhanced protocol for the quarantine detection of Tilletia indica and economic comparison with its current standard

Tilletia indica, the cause of Karnal bunt of wheat, is the target of strict quarantine regulations by most wheat-growing countries and its presence raises trade barriers to wheat exports. The international diagnostic protocol currently used in Australia involves the tentative identification of the spores based on morphology followed by germination of the spores and a molecular protocol to confirm the identity. This paper reports on the development of an enhanced protocol by the incorporation of a highly sensitive one-tube molecular assay for T. indica and related Tilletia species found as grain contaminants. The enhanced protocol reduces the amount of time and labour required in microscopy and bypasses the germination of Tilletia spores in the processing of samples. An economic analysis has been performed to compare the economic costs of the current and the enhanced protocol and their relative performance in different scenarios. The results indicated that the current protocol would be more economical in the monitoring and identification of T. indica in current infested areas. However, the enhanced protocol is significantly more economical and sensitive for use in an exotic pest incursion scenario or a survey to demonstrate area of freedom. The enhanced protocol also reduces the elapsed time before a definitive identification can be achieved.