Several plants attacked by Synchytrium fulgens exhibit the resistance termed by Stakman as hypersensitiveness. In the course of the intracellular development the parasite suffers sooner or later from the necrobiosis and finally, as a manifestation of death, semipermeability of its protoplasm vanishes and causes shrinkage of its body. At this moment the host cell is still alive. The substances released from the dying parasite are considered to act upon the host cell detrimentally and to kill it immediately. Thus, it may be said that the host cell kills the parasite and in turn is killed by the dying parasite. Therefore, the death of the host cell does not participate in in ducing the resistance.
The fine structures of conidia of Cochliobolus miyabeanus were investigated by electron microscopic observations of ultrathin sections of conidia fixed in a solution of 2per cent permanganate buffered with veronal acetate to pH 7.4 and the results were shown in Figs. 1∼7. Fig. 1. General view of a conidium. The conidium was cut parallely to the long axis of cell. Fig. 2. Higher magnification of a small area (cf. rectangle in Fig. 1). Note the different orientation of cellulose microfibrils in outer and inner layers. Fig. 3. Various profiles of mitochondria and endoplasmic reticulum. Fig. 4. General view of nuclear area. Fig. 5. Portion of protoplasmic junction. The junction was cut parallely to the long axis of the cell. Fig. 6. Portion of protoplasmic junction. The junction was cut perpendicularly to the long axis of cell. Fig. 7. Diagrammatic view of conidium of Cochliobolus miyabeanus reconstructed from the data obtained. C: cytoplasm N: nucleus CW: cell wall NM: nuclear membrane ER: endoplasmic reticulum OL: outer layer IL: inner layer PJ: protoplasmic junction M: mitochondria PM: protoplasmic membrane
In the present paper, the writer deals with the experimental evidence on the cause of so-called “vascular browning”, which is induced in the watermelon tissues infected by Fusarium oxysporum f. niveum. Microchemical observations on the injured tissues showed that, in the early stage of the disease development, the discoloration was limited to xylem parenchyma, wherein remarkable increase of phenolic substance and abnormal activation of phenoloxidase were noticeable, and was severely on progress in advance of the invading hyphae into cells, that the browning of cells seemed not to play an important role for a chemical barrier to invading hyphae, since the growth of mycelium in the browned cells was also recognized in the later stages of the disease development. Salicylic acid and another phenolic substance were isolated from watermelon roots as a vascular browning precursor. And the qualitative and quantitative changes of the precursors in the tissues during the infection process were assayed by using spectrophotometer and paper electrophoresis (Figs. 4 and 5). Fungal pectic enzyme, being functional in producing cell maceration, and fusaric acid that is toxic to the cell, might be indirectly responsible for the browning in vivo. Effects of salicylic acid and the related compounds on the growth of the causal fungus were investigated. From the results, it was shown that the antibiotic action of salicylic acid was dependent on the COOH radical rather than the OH.
A new leaf spot disease of corn (Zea mays L.), “Kappanbyo” has been found to occur in Hokkaido since 1956. Round, brownish gray spots, 1∼3mm. in diameter, with brown or brownish purple margin and light yellow halo are found numerously on leaf blades, leaf sheaths or rarely on stems of corn plants. The causal fungus does not attack any plant other than corn plant. From the results of the studies on the morphological characters of the fungus, it is considered that the fungus is a new species belonging to the genus Kabatiella Bub. emend. Karakulin. The technical description of the causal fungus, Kabatiella zeae Narita et Y. Hiratsuka, is given.
The purpose of the present experiments was to make clear the nutritional requirement for the sporulation of Phytophthora infestans on the artificial culture. Most of the work to be described has been carried out with the use of isolates H1 and H3 of P. infestans, the first being isolated in 1954 from the naturally infected leaf of potatoes of the variety Irish Cobbler and the second in 1954 from Kennebec at Kotoni in Hokkaido. The experimental results obtained may be summarized as follows. 1. P. infestans produced the highest number of sporangia on the bean-meal agar of the following formula: 50g ground dry beans (Phaseolus vulgaris L. “Kintoki”), 10g sucrose, 10g agar-powder and water to make 1 liter. However, an addition of the bean meal extracts to potatodextrose agar did not increase sporangial yield. It seems to indicate that the fungi needs no specific substance to promote sporulation. 2. An addition of alanine to potato-dextrose agar containing 1 per cent sucrose caused little change in mycelial growth, but a great increase in sporulation. However, it caused no increase in sporulation of the fungus on bean-meal agar. 3. Among the constituents of the medium, the balance of nitrogen and sugar is the most important in sporulation of P. infestans. The favorable ratio of the carbon-nitrogen elements of the semisythetic medium in sporulation is about 7.7. In the present experiment, the optimum concentration of carbon and nitrogen sources in the basal medium appears to be at about 1 per cent sucrose and 0.2 per cent L-arginine monohydrochloride.
The absorption and translocation of streptomycin in the tobacco plant was investigated by radioautographs of S35 labelled streptomycin sulphate absorbed by the plant. (1) It was found that there was little movement of streptomycin in the leaves when absorbed through the leaf surface. Some movement was observed towards the leaf tips when the streptomycin was applied to the mid-rib or large vein. (2) Movement into the xylem, followed by translocation to the upper leaves, was exhibited when the streptomycin was absorbed in cotton-wool and banded around bottom of the plant stem. When the streptomycin was absorbed in large amounts, translocation to the lower leaves was slow and the higher leaves contained a larger proportion of the streptomycin, though dependent on the total amount of streptomycin absorbed in the stem, the lower leaves often contained more than the middle leaves. (3) The results obtained from these radioautograph experiments were similar to those from the bio-assay of the leaf sap using the cup method and inoculation test with Pseudomonas tabaci. (4) Within twenty-four hours of applying streptomycin to the lower stem, it was translocated to the upper leaves.
In the previous reports, abnormal phosphorous metabolisms were observed in both the dwarf virus-infected mandarin plant and the virus transmitting-green broad winged planthopper. This paper deals with the experiments to elucidate the rate of incorporation of P32 into the phosphorous fractions in these abnormal metabolisms. (1) The radioactivity of P32 in various phosphorous fractions of mandarin plant or planthopper shows relatively higher level, as affected with the virus (Tables 1∼2). (2) The acid soluble phosphorous compounds of the examined material were fractionated by the method of LePage and Umbreit. In both the plant and the insect, the amounts of phosphorous contents in the various fractions show no consistent difference in trend between healthy and diseased individuals. The radioactivity in each fraction of the viruliferous insect is, however, found on considerably higher level than that of the nonviruliferous one (Tables 3-4 and Figs. 1-2). (3) The nucleic acids examined were extracted by the method of Ogur-Rosen and Schneider from orange plant, and by the Schneider's method from planthopper. The incorporation of P32 into the nucleic acids is considerably lower rate, and the autoradiograms present no difference between healthy and diseased plant or between nonviruliferous and viruliferous planthopper, respectively (Figs. 3∼4). It is suggested that the nucleic acid is to be prepared a more suitable technique under milder conditions.
(1) Cellulase (Cx) of phytopathogenic bacteria, twenty-eight species and one variety belonging to five genera, was detected when they were cultured on CMC-gel medium prepared by dissolving 2 percent of carboxymethyl-cellulose (CMC) into various basal media (Table 1). Cx enzyme was commonly produced by xanthomonads and all strains of Erwinia carotovora, serologically identified by the authors, though they show various degrees of activity according to each bacterium, while most pseudomonads, except P. solanacearum and P. panici, did not show the production of cellulase (Cx) on any medium tested. Erwinia milletiae and Corynebacterium sepedonicum produced the enzyme on only potato-CMC-gel medium, the most suitable one for the detection of cellulase (Cx), prepared by adding CMC into potato decoction (see Table 2). (2) The cellulase (Cx) activity of phytopathogenic bacteria was represented by percent loss in viscosity of one percent solution of CMC. It reacts with the reaction of linear equation, since reaction time necessary for reaching to fifty percent-loss in viscosity of CMC solution did not connect with the concentration of the substrate (see Table 3). (3) Change of cellulase (Cx) activity in filtrate of 10 days culture in bouillon or potato decoction with or without CMC, was different corresponding to the bacterial species or strains tested (see Fig. 1). When the velocity constant k of the linear equation is adopted as the standard of the enzyme activity, cellulase (Cx) in culture filtrate of bouillon or potato decoction containing 0.2 percent CMC increased its activity in a straight line with the culture duration in the case of Erwinia carotovora strain chrysanthemi. In the case of Xanth. campestris, however, the conspicuous decrease of activity followed its very rapid increase within 3-day-incubation period (see Fig. 2). Although the probable production of a proteinase is responsible to such prompt decrease of cellulase activity, its presence may be made evident elsewhere. In the case of Pseud. solanacearum the activity was observed to increase in a straight line during five-day incubation, but then stabilized at this level until 10 days. This stabilization of enzyme activity of P. solanacearum is supposed to be caused by the rapid loss in vitality of this bacterium usually occurring in bouillon or potato decoction medium. Cellulase (Cx) was produced under the cultural conditions without CMC (β-1.4 glucosidic linkage), though the activity was relatively low as compared with that under its presence.
(1) The effect of pH on the activity of cellulase (Cx) was tested with the one-percent CMC solution prepared by Mc'Ilvain buffer solution varing in pH value from 3.0 to 8.0. The change of enzymic activity was shown by the percent loss of viscosity after 30 minutes of reaction time. The optimum pH value was varied from 5.0 to 7.0 corresponding to the bacterial species which produced the enzyme (see Fig. 1). In general, the enzyme was very unstable in pH 3.0 and rapidly inactivated. (2) It was evidenced that the effect of temperature on cellulase activity, which was represented by the percent loss of viscosity of the mixture of one-percent CMC solution and 7 day-old culture filtrate, was remarkable in higher temperatures between 30 to 60°C tested (see Fig. 2). (3) The effect of five kinds of salts on the cellulase activity was variable according to the bacterial species or strains tested (see Fig. 3 and Table 2). Some salts, recognized as having a promoting effect to the activity of cellulase (Cx) secreted by one bacterium, were obstructive to those from other bacteria.