Drops of conidia suspension of Piricularia oryzae were mounted on the detached leaf pieces of rice plant, at the points pricked by capillary glass tube, and kept at 25-28°C for 24 hrs. in the moist chamber. These drops were then collected and centrifuged for 20minutes by 3000rpm. The supernatant of these drops showed strong inhibiting action against the germination of conidia of this fungus. The active principle, phytoalexin of Müller, is considered to be produced by the host plant as a result of interaction between rice plant and the blast fungus P. oyyzae. In the experiment to see the quantitative difference of phytoalexin prodcution between resistant or susceptible varieties of rice plant to blast fungus, it was shown that phytoalexin was more vigorously produced in the resistant varieties (Kameji and Norin No. 22)than in the susceptible ones (Asahi and Omachi).
The writer already reported that large quantity of free auxin was contained in the gall tissue of the stem and leaf of Youngia japonica infected with Protomyces inouyei, though the determination of the hormonal substance was not yet done. This article deals with the results of experimental studies on the production of auxin and its identification regarding 3 species of Protomyces fungi. Four kinds of solvents such as ether, chloroform, ethyl-alcohol and water, were used for obtaining extract from the gall formed by the infection of Protomyces inouyei. With these extracts Went's Avena-test was carried out. The ether solvent was found to be better for the purpose of extraction than others, as shown in Table 1. When Protomyces was cultured in Czapek's solution or in the same one containing 1g of L-tryptophane in substitution for KNO3 as a N source, the filtrate from the latter medium alone was ascertained by the Avena-test to contain a considerable quantity of auxin. The material fungi were cultured in Czapek's medium containing tryptophane, at 26°C. for 30 days, and their filtrates were concentrated to one half. The filtrates were then extracted with trebled volume of ether, and the dry yellowish extract was obtained from P. pachydermus and the yellowish brown one from other two fungi. The yellowish brown extract showed typical IAA color reaction with Gordon and Weber's reagent, while the yellowish one never showed the reaction. For analysing the extract one-dimentional paperchromatography was applied under the condition as described in the foot-note of Table 4. The reddish pink spots at Rf 0.54 and 0.55 developed by isopropanol-ammonia-water solvent mixture and also the spots at 0.79 and 0.80 developed by ethanol solvent were all identified as IAA, by comparing with the Rf value shown by synthetic IAA as the control. The IAA spots appeared was found to be smaller in area than other spots. Figure 1 shows the data of analysis of these extracts by the paperchromatographic bioassay method. The results also clearly show the presence of IAA similarly to the experimental data mentioned above. It seems to the writer that Protomyces may produce tryptamine and indoleacetaldehyde as the intermediates in the metabolic process of tryptophane, because some similar spots to the very intermediates in respect of color reaction and Rf value were shown in the paperchromatogram. Protomyces fungi were proved to have lower activity in IAA metabolic production from tryptophane than certain various fungi belonging to Ustilago, Taphrina, Exobasidium, Fusarium etc. as far as the writer's experiments concerned.
稲胡麻葉枯病病斑上より分離したB. funicularis Kluyver et Van Nielの培養濾液は胡麻葉枯病菌分生胞子の発芽を著しく抑制する。この抗黴性物質をFunicularinと仮称したが,該物質の生産は,pH 6～7のブイヨン培地で25°～30℃下に4日間培養が最良である。Funicularinの抽出及び精製法は第1図に示したとおりであるが,Funicularinを加えたブイヨン培地で供試菌を継代培養すると,母菌株の抗黴性物質の生産力は一層増高される。なお本細菌培養濾液中に根部浸漬した稲苗は,無処理苗に比べて稲胡麻葉枯病菌に対する感受性が低下する事を認めた。