Accurate assessment of wheat and triticale cultivar resistance to Septoria tritici and Stagonospora nodorum infection by biotin/avidin ELISA

Specific and quantitative biotin/avidin-enzyme-linked immunosorbent assays (BA-ELISA) were evaluated for their ability to assess resistance of wheat and triticale cultivars to Septoria tritici (leaf blotch) and Stagonospora nodorum (leaf and glume blotch) in field trials. Using BAELISAs, the antigen amounts of S. tritici and of Stagonospora nodorum were measured in the flag leaf (F) and the first leaf below it (F-1) of five cultivars of triticale at Zadok's growth stage (GS) 75-80 and in 11 cultivars of wheat at GS 73-75 in 2001 and 2002. The presence of the pathogens was found to be specific to parts of the plants, cultivar, and plant species. Stagonospora nodorum was the dominant leaf blotch pathogen in triticale, while both Septoria tritici and Stagonospora nodorum occurred commonly in wheat. Close correlations were obtained between the pathogen amount measured by BA-ELISA and the percentage of necrotic leaf area in the tested cultivars. The BA-ELISA values for the tested triticale and wheat cultivars were ranked, and they correlated well with the susceptibility ratings given in the cultivar list recommended by Bundessortenamt (German Federal Office of Plant Variety), which is based on visual assessment of the leaf blotch complex caused by S. tritici and Stagonospora nodorum. The relative susceptibilities of individual wheat cultivars to both pathogens were similar. In conclusion, BA-ELISA provided for an accurate diagnosis and quantification of S. tritici and Stagonospora nodorum in infected plant tissue, and therefore can be used to assess resistance to these fungi in a disease complex in both early-stage breeding lines and field trials.