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.
The rice blast fungus was cultivated on the medium containing glutamic acid as the sole source of carbon and nitrogen. The fungus grew well on that medium. The maximum yield of the mycelium per gram atom of carbon was 87per cent to that of the one grown on the medium containing sucrose and nitrate. But with respect to heat of combustion driven from each mole of these carbon sources, the growth of the fungus were almost equal in both cases. The pathway of the glutamic acid was studied by means of the inhibition with arsenite and also under the deficiency of thiamine. α-Ketoglutaric acid was isolated as 2.4-dinitrophenylhydrazone from the medium. Glutamic acid is assumed to be metabolized through TCA-cycle by this fungus.
The results in the previous paper suggested that the accelerated metabolism resulting in acceleration of protein synthesis accompanies the resistant reaction of potato tuber to the infection by P. infestans. In the present studies, several experiments were designed to ascertain the facts in respect to this problem. Cut surface of potato tuber of interspecific hybrid “Hokkai No. 10” was inoculated with zoospore suspension of incompatible strains of P. infestans, H1 and H2, to which the variety examined is highly resistant, and with that of compatible strains, H3 and H7, to which the variety is susceptible (Table 1). Then physiological changes in the infected tissue were examined. Ten, 15, 20 and 35hrs. after inoculation remarkable increase in O2 uptake had taken place in the tissue infected with H1 and H2, but not in the tissue infected with H3 and H7. At the same time increase in water soluble protein-N, and polyphenol content was observed in case of resistart reaction It may be concluded that the increase in soluble protein and polyphenol compounds indicates the actual synthesis that has been resulted from excited metabolism induced by infection with P. infestans. The present studies suggest that the resistance of plants to pathogen may be understood as a general reaction of living organisms to the injury, the process of which is given diagramatically in Fig 2.
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.
Observations were made on the colony development of Erysiphe graminis hordei on varieties of barley, using entire inoculated leaves, after fixing and clearing in formalin-acetic-alcohol and staining with acid Fuchsin. On susceptible varieties, the hyphae usually grow along the periclinal lines of epidermis and form a colony of rectangular, finally elliptic, periphery. About six days after inoculation, conidium formation begins at the center of the colony and later it extends to the margin. There appear convolute hyphae at the margin of the colony along the long axis; these hyphae, developing less appressoria and haustoria in number than the ordinaly hyphae, do not generally adhere tightly to the leaf surface. On comparatively resistant varieties, thin colonies of triangular, semi-circular, shovel-like or dumbbell form in shape, are commonly found. At an earlier stage of colony growth than the cases on susceptible varieties, conidia and convolute hyphae were often produced. Conidium formation, however, was sparse in accordance with the poor development of hyphae. Browning of host tissues beneath the infection court were frequently observed.
1) In a survey for the cucumber mosaic virus., 573 collections of mosaic plants have been made in the years from 1949 to 1955 in the vicinity of Tokyo, from 150 species of plants belonging to 47 families, and inoculated on the differential hosts. Of these collections, 202 samples (35%) from 68 species of plants (45%) in 32 families yielded the cucumber mosaic virus. 2) Among the hosts previously reported as naturally infected, 37 species were confirmed, in which, cucumber, muskmelon, tobacco, Primula sinensis, P. obconica, celery, pansy, Silene armeria, Stellaria media, Amaranthus blitum, beet, spinach, Commelina communis and corn are worthy to mention, as they are grown relatively common in Japan, and mosaic plants of them yielded the virus in higher percentage than 50. While, the cucumber mosaic virus was isolated hardly or not at all, from the following species: chrysanthemum, Campanula grandiflora, dahlia, marigold, red pepper, Physalis Alkekengi, bean, pea, Iris germanica, narcissus, hyacinth, tulip, calla, and lilies. 3) Thirty-three species and varieties of plants, previously unreported as hosts in nature, were found infected in the field. These were Chrysanthemum carinatum, Trichosanthes cucumeroides, Cucumis melo var. Makuwa, Luffa cylindrica, Myosotis scorpiodes, Cynoglossum amabile, Asclepias curassavia, Vinca rosea, Primula malacoides, P. veris, Cryptotaenia canadensis, Godetia amoena, Impatiens Balsamina, alsike clover, Raphanus sativus, Brassica rapa var. Komatsuna, B. napus, B. cernua, B. pekinensis, cabbage, Dianthus chinensis, D. superbus, Lychnis coronaria, Gypsophyla elegans, Cerastium vulgatum, Portulaca oleraceae, Gomphrena globosa, Amaranthus tricolor, buckwheat, Zingiber Mioga, Tradescantia reflexa, Pollia japonica, and Colocasia antiquorum. Among them, Chrysanthemum carinatum, Cucumis melo var. Makuwa, sponge gourd, Cryptotaenia, radish, buckwheat, and Colocasia are grown rather common in the gardens, and have been found infected frequently by the cucumber mosaic virus. 4) Occurrence of mosaic plants of Commelina communis, Stellaria media, Trichosanthes cucumeroides, Cerastium vulgatum and Zingiber Mioga by cucumber mosaic virus are sufficiently common to be regarded as a part of source of infection.
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.
(1) The present paper deals with the proximate analysis of the mycelium of Gloeosporium Olivarum and also nutrient absorption by the pathogen, with particular stress on the effect of sodium 2, 4-dichlorophenoxyacetate. (2) Proximate analysis of the mycelium showed that hot water extract, dilute HCl extract and residue after successive extraction are much higher in the 2, 4-D culture than the control. Hemicellulose and chitinlike substances probably account for the increase of the latter 2 groups. On the other hand, the significant decrease of ether extract and cold water extract was observed in the 2, 4-D culture, indicating that energy rich materials of a lipide nature and also the water soluble substances, known to have a close relation with metabolism, may contribute to the lower values of these fractions. Total nitrogen showed little difference between mycelia grown on media with or without 2, 4-D. (3) As might be expected, the absorption of glucose and nitrogen from the medium was strikingly suppressed in the case of the 2, 4-D culture where the mycelial growth was restricted. However, grams absorbed per gram cell material synthesized become high by the presence of 2, 4-D. This significant increase of nitrogen absorption in media 2, 4-D added despite its lower content in the mycelium suggests that an abnormal nitrogen metabolism is severely undergoing.
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.