Physiological Specialization of Gibberella saubinetii (MONT.) SACC., in its Pathogenicity to Wheat Seedlings

Abstract

The present paper is an introductory report of the writers' studies on the Fusarium-blight of wheat, caused by Gibberella saubinetii (MONT.) SACC. (Fusarium graminearum SCHWABE), and deals with the physiological specialization of the causal fungus.
The fungus attacks wheat, barley and other cereals and causes not only the head-blight but also the seedling-blight everywhere in Nippon (Japan). It is one of the most serious menace to the wheat industry in our country.
The physiological specialization has been proved to be common in many of pathogenic species of Fusarium, and the studies on this problem are important. Therefore the writers began their investigation on this phase of the causal fungus. One hundred and twenty four strains of Gibberella saubinetii (MONT.) SACC. were isolated from the diseased ears of wheat and barley, which were sent to the writers from various parts of Nippon. The pathogenicity of these strains was studied by inoculation experiments. After surface disinfection, wheat grains inoculated with the conidium suspension of each of these strains, and were sown in sand in flowerpots, which were previously sterilized under fifteen pounds pressure for from two to four hours. The percentages of the germinatel wheat grains, and of the diseased seedling affected after the germination were studied by triplicated inoculation-experiments. An example of the results is given in Table I.
For the comparison of pathogenicity of each of the Fusarium strains to wheat seedlings, the writers preferred the percentages of the healthy seedlings secured, to the total wheat grains sown. The mean percentages of the healthy seedlings developed from the inoculated grains were computed, together with the differences between each of these mean percentages and that of the uninoculated control wheat, and the ratios of these differences to their probable errors. The results are given in Table II.
The figures in Table II show that some of the strains tested were very strong in their pathogenicity to the wheat seedlings. The differences between the mean percentages of healthy seedlings of some strains and that of the control are 20 to 50 times of their probable errors. Evidently such strains are strongly pathogenic to wheat, at least under the circumstances tested. On the other hand, in some strains the differences are only under three or five times of their probable errors. These strains should be assumed to be non-pathogenic to wheat. Between the strains showing the extremely strong and weak pathogenicity, a number of strains of intermediate strength are found, according to these results.