Five phenolic compounds were isolated using paper chromatography from the tissue affected with rhizome rot fungus of lotus, Fusarium bulbigenum var. nelumbicolum (table 1 and figure 1). The compounds were found to exist as much in the resistant variety (Shina) as in the susceptible (Usu), except two of them existed comparatively less in the latter variety. Healthy inner tissue of rhizome contains less of such compounds, whereas healthy epidermal tissue contains the same amount as affected tissue (table 2). One of the compounds was identified as chlorogenic acid from its ultraviolet absorption and by use of various reagents (table 3 and figure 2). Juice prepared from the tissue near the infection showed a inhibitive effect against spore germination of the causal fungus, although when boiled they lost the ability (table 6). Juice from the healthy tissues both inner or epidermal had little effect (tables 4 and 5). Abnormal metabolism in the tissue near the infection in resistant variety were also investigated. The results were as follows: 1) The amount of inorganic phosphorus compounds was less in the tissue just beyond the infection than in the healthy, and that of acidsoluble organic phosphorus compounds was much in the former, especially in resistant variety. Concerning the amounts of nucleic acid, lipid, and protein phosphorus compounds, no determinative results were obtained (tables 8 and 9, figures 3 and 4). 2) Dehydrogenase activity in the resistant variety was somewhat higher than in the susceptible and it was raised two days after infected (table 10). 3) More increased rate of respiration was observed in the tissue near the infection than in the healthy tissue, especially in resistant variety (table 11 and figure 5). 4) Phosphatase activities showed an increase from 36 to 60 hours after infection in resistant variety (table 12 and figure 6). The results just outlined would suggest that the phenolic compounds found in the tissue near the infection have no closer correlation with a inhibitive action of resistant variety against the causal fungus. Rather than this, numerous efforts must be paid in future to confirm the abnormal metabolism between host-parasite interaction, only in which the basic mechanism of resistance in plants may be sought.
It this paper, the results of the experiments on the growth factors of rice stem rot fungi (Leptosphaeria salvinii Catt. and Helminthosporium sigmoideum var. irregulare Cralley et Tullis) are noted. These fungi made no growth on the synthetic media, composed of sugar and inorganic salts, but good growth was obtained by adding rice straw decoction which seemed to contain growth factors. It was demonstrated that Biotin and Thiamine were essential for the growth of these fungi. Glutamic acid, aspartic acid, glutamine and asparagine are shown to serve for accessory growth factor as well as excellent nutrient source. The adequate amount of the main growth factors were as follows: Biotin 0.001γ/cc for Leptosphaeria fungus, 0.005γ/cc for Helminthosporium and Thiamine 1.5γ/cc for both fungi. But the optimum of the accessory growth factors are not yet determined. In general, mono-amino-dicarboxylic acid had a growth promoting effect, while mono-amino-monocarboxylic acid a little or no. Alanine seemed to inhibit the growth of the two fungi tested. Pyridoxin nicotinic acid, riboflavin, inositol and pantothenic acid which have been reported to be the growth factors for many other fungi, had shown no growth promoting effect in the present experiment.
In the past the sooty mould fungi belonging to the Capnodiaceae have been described as having various types of pycnidia, pycnospores and conidia, i. e. Microxyphium including Stylospora and Spermatium, Chaetasbolisia, Antennularia, Triposporium, Fumago, Brachysporium and others. These spore types in the imperfect stage of each sooty mould fungus are extraordinarily diverse since two or more species of the sooty moulds and other fungi often grow together in the same mould colony, and produce various spore types mentioned above on it. Consequently, the proper spore type in the imperfect stage of each species or genus of the Capnodiaceae have hardly been determined yet. For the purpose of confirming the relationship of the spore types between the perfect and imperfect stages of the sooty mould fungi, the single spore cultures have been made from the ascospores, pycnospores and conidia of sooty mould fungi belonging to the genera of Capnodium, Neocapnodium, Aithaloderma, Triposporiopsis, Limacinia, Hypocapnodium, Chaetothyrium and Phaeosaccardinula. The results of the comparative studies made on the conidia or pycnospores produced on each mould colony growing in the culture media revealed that the spore types in the imperfect stage of these genera were as follows. The spore types of the genera of Capnodium, Neocapnodium, Aithaloderma and Triposporiopsis are Stylospora, Spermatium, Chaetasbolisia and Triposporium, respectively. Although the genera of Hypocapnodium, Chaetothyrium and Phaeosaccardinula have neither pycnospore nor conidium, Limacinia rarely has Antennularia type. Both types of Fumago and Brachysporium mentioned above do not connect with the Capnodiaceae, but belong to the Deuteromycetes.
The 140 antifungal actinomycetes, which had been selected from 7243 strains in Tokyo University, were tested in our laboratory in relation to their antifungal activity against seven plant pathogens; Piricularia oryzae Bri. et Cav., Ophiobolus miyabeanus Ito et Kuribayashi, Gibberella saubinetii (Mont.) Sacc., Ceratostomella fimbriata (E. et H.)Ell., Alternaria kikuchiana Tanaka, Glomerella cingulata Spauld. et Schr., and Fusarium lini Bolley. As shown in Tabe I, many actinomycetes showed strong inhibitory action against one or more of the seven test plant pathogens in of 12 strains agar disc diffusion tests. The antifungal spectra of actinomycetes, which were found to be highly effective on P. oryzae, are given in Table 2. The 40 strains of actinomycetes, which showed high antifungal activity on P. oryzae, were cultivated in shaken liquid modified Waksman media at 28°C. The antifungal activities of culture fiitrates at three and five days were tested by cup method. Data obtained are given in Table 3. Twelve strains were selected on the basis of the size and clearnesss of the inhibition zone around the cup. The effect in vivo of 12 strains, which were found to be effective in vitro on rice blast fungus, were studied in greenhouse tests. As shown in Table 4, the culture filtrates were found by slidetests to be capable of inhibiting the germination of conidia. Rice plants showed an increase in resistance to the rice blast when cultured in water added with filtrates of actinomycetes culture at two to seven days or sprayed with diluted filtrates. The number of leaf-spots were remarkably less than in the untreated plants, as shown in Table 5 and 6. As the result of these tests, two active strains were selected as the most promising anti-blast actinomycetes among the 140 strains.