Tilletia indica

A quarantine procedure for testing seeds of Triticum spp. for T. indica has been described by EPPO (OEPP/ EPPO, 1991b). An EU recommended diagnostic protocol for the detection and identification of T. indica has also been produced (Inman et al., 2003;EPPO, 2007). This protocol has been enhanced for increased sensitivity and specificity by the adoption of more advanced technology (Tan et al., 2010). An updated draft is available from the IPPC website (www.ippc.int).
Crops for seed should be inspected during the growing season, though not while the crop is still green. Field inspection at maturity prior to harvest could be useful, although field symptoms are often very slight and the disease can be difficult to discern even at maturity. Any bunted seeds detected during field inspections should be examined under the microscope for the characteristic teliospores of T. indica. For quarantine purposes, seed should be tested for the presence of the fungus by the washing test (see Seedborne Aspects).
Direct visual observation for Karnal bunt (dry seed inspection) is regarded as insufficient for quarantine purposes because low levels of infection might pass undetected (Agrawal et al., 1986) and even minimal seed infections can substantially contaminate healthy seed lots (Aujla et al., 1988).
Being a non-systemic pathogen, it generally produces not more than four or five bunted kernels in each spike. Detection in the field is very unlikely and the first year of an outbreak usually goes undetected. For instance, detection of T. indica in a seed test sample in Arizona, USA, in 1996 was traced to wheat harvested in 1993 suggesting the pathogen had been present since 1992 (Rust et al., 2005). It had taken at least 4 years for the pathogen to be detected.