Predisposition to Septoria nodorum as a result of take-all (Gaeumannomyces graminis) infection of wheat

In a series of experiments excised leaves from take-all infected wheat plants and from control plants were inoculated with Septoria nodorum. Larger lesions, more lesions/leaf and more pycnidia/unit area of lesion were produced from take-all plants. Significant effects of predisposition were demonstrated when only 3% of the area of the total root system was infected by take-all. Microscopical investigations revealed that germ-tubes of S. nodorum grew more rapidly on leaves from take-all plants, but the time of penetration was not affected. It is proposed that the observed effects of predisposition arose because more germ-tubes produced successful infections and host tissue was more rapidly colonised. The importance of these results for the epidemiology of glume blotch is discussed.