Evaluation of visual assessment of leaf symptoms and of an enzyme-linked immunosorbent assay as tools for the characterisation of resistance of winter wheat against common bunt (Tilletia tritici [D.C.] Tul. & C. Tul.)

Using 30 winter wheat varieties, leaf symptoms indicating infection with common bunt (Tilletia tritici) as well as an enzyme-linked immunosorbent assay (ELISA) based on polyclonal antibodies were evaluated for early assessment of bunt susceptibility/resistance. The percentage of plants with leaf symptoms recorded at growth stage 14 was in most varieties higher when the plants were germinated at 15°C than at 4°C, and the percentage of symptomatic plants was on average higher in the susceptible than in the resistant varieties. However, due to large variability a general relationship between leaf symptoms and varietal resistance could not be established. It is concluded that leaf symptoms are not generally suited to predict the degree of susceptibility to bunt, irrespective of the temperature at which the plants are geminated. Much better results were obtained with quantification of the pathogen in wheat seedlings by ELISA. In all susceptibility groups and varieties the fungal content of individual plants was highly variable. However, on average the plants expressing early symptoms contained twice as much antigen as the plants without symptoms, and the very highly susceptible varieties contained on average approx. five times as much antigen as the very lowly susceptible ones. While due to high variability it may be more difficult in routine use to accurately assign with the ELISA the varieties of intermediate susceptibility, it is expected that it will be possible to clearly differentiate the lowly and very lowly susceptible varieties from the more susceptible ones, provided a sufficiently large number of plants is assayed.