Reaction of Australian durum, common wheat and triticale genotypes to Karnal bunt (Tilletia indica) infection under artificial inoculation in the field

Karnal bunt is a seedborne disease of wheat caused by the fungus Tilletia indica Mitra and is a major biosecurity threat for the Australian wheat industry. Host-plant resistance is an effective means of controlling this disease. This study has identified Australian wheat genotypes with durable resistance should the pathogen enter Australia and become established. These genotypes provide a basis for breeding adapted genotypes that can be recommended for growers. In the study, 196 genotypes comprising 177 common (bread) wheat (hexaploid, Triticum aestivum), eight durum (tetraploid, T. durum) and 11 triticale (x Triticosecale) genotypes were evaluated in the field for their reaction to infection by the fungus. Six experiments were carried out at CIMMYT's research station at Obregon, Mexico, during three consecutive cropping seasons (2014-15, 2015-16 and 2016-17) and at two planting dates. In each experiment, the genotypes were screened for resistance to Karnal bunt by injecting an inoculum suspension with a hypodermic syringe into the boot at awn emergence. Disease incidence averaged 14.7% infection in 2015, 21.7% in 2016 and 25.6% in 2017. Resistant triticale genotypes, Tuckerbox, Berkshire and Hawkeye, were identified, along with three resistant wheat genotypes, Batavia, Pelsart and RAC-655, and two moderately resistant durum genotypes, Hyperno and Saintly. Stability analysis showed that RAC-655, Hyperno, Tuckerbox and Berkshire were consistently resistant to infection in different seasonal conditions and unaffected by the environment.