Characterization of leaf symptoms of common bunt (Tilletia caries) and relationship to ear attack in nine wheat cultivars

The reaction of nine winter soft wheat cultivars to infection by the bunt fungus Tilletia caries was evaluated in two pot tests and in the field. In the first test (planting date Sept. 25), the pots were incubated after seedling emergence for about 4 weeks at 20 degreesC before they were transferred to an unheated greenhouse. In the second test (planting date Nov. 15), the pots were placed in the unheated greenhouse immediately after seedling emergence. In both tests, the pots were transferred to the field in the following spring. In the First pot test, plant development was faster, symptoms of T caries infection on leaf blades and sheaths appeared earlier, and ear attack with bunt was lower than in the second test. In the more resistant cultivars, the time period until early symptoms became visible was longer, and the percentage of plants expressing early symptoms as well as the ratio "% plants with bunted ears : % plants with leaf symptoms" was lower than in the susceptible ones. For example, the cultivar 'Bussard' had a high percentage of plants with early symptoms and a high percentage of plants with ear attack. In the cultivar 'Tanibor', the percentage of plants with leaf symptoms was initially low but increased considerably. Ear attack in 'Tambor' was nevertheless low in both pot tests, indicating that the degree of attack by T. caries is determined not only by the degree of initial infection but also by the ability of the fungus to spread within the plant. In field experiments performed at two locations, 'Tambor' was clearly the most resistant cultivar, followed by 'Aron'. 'Toronto' and 'Zentos' showed some degree of resistance, white 'Monopol', 'Alidos' and 'Batis' were susceptible. In case of 'Bussard' and 'Glockner', the reaction to bunt differed between the two locations.