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The whole cycle of fungal growth of Diaporthe citri, i.e., pycnospore germination, appressorial formation, hyphal penetration, penetrated mycelia, pycnidium formation and pycnospore formation was observed on alcohol-treated epidermal strips of onion bulb which might be free from some inhibitors against hyphal penetration. The results obtained on epidermal strips of onion bulb were nearly same as those obtained on citrus leaves or twigs. Therefore, the method using epidermal strips of onion bulb would be very useful for assaying the effects of fungicides on the different growth stages of D. citri. The maximum rate of pycnospore germination was approximately 80 to 100% and that of hyphal penetration was approximately 50 to 70%. The shapes of appressoria were mostly fist-like or globular form and they did not necessarily have relation to hyphal penetration. Therefore, the function of appressorium of D. citri seems to adhere on host plants, but the role does not seem to be so important, judging from the fact that the appressorial formation rate is only 20 to 30%. When suspension of pycnospores in pycnidia formed on epidermal strips of onion bulb was inoculated on young citrus leaves, typical symptoms of melanose were observed, indicating that the pycnospores were virulent.

The degradation of N-lauroyl-l-valine in soil and the effects of sunlight and ultraviolet radiation on this compound were studied. When N-lauroyl-l-valine was added to the soil extract, a precipitate was observed. The precipitate was thought to be a salt formed from one calcium atom and two molecules of N-lauroyl-l-valine. These data indicated that N-lauroyl-l-valine was absorbed firmly in the soil. Qualitative analysis of compounds formed during incubation of soil with N-lauroyl-l-valine was investigated by gas chromatography. Laurie acid (C12) and capric acid (C10) were detected in the medium after incubation. The amino acid could be determined quantitatively by a microbial assay method. The experiment using N-lauroyl-l-valine (14C) indicated that 14CO2 was produced as a final product. These data suggested that N-lauroyl-l-valine was spilt to lauric acid and l-valine, and the lauric acid was degraded to CO2 through capric acid by β-oxidation. The parent compound, N-lauroyl-l-valine was stable to sunligh...

As a part of studies on the mechanism of action of antibiotics polyoxins, effects of various N-aminoacyl derivatives of polyoxin C and other polyoxins on chitin-UDP acetylglucosaminyl-transferase (EC 2.4.1.16, chitin synthetase) prepared from phytopathogenic fungus Piricularia oryzae were investigated. It was found that they inhibited the enzyme in competition with the substrate UDP-N-acetylglucosamine, Inhibitor constants, Ki, for these polyoxins were determined and the values of binding affinity, −ΔGbind of the inhibitors to the enzyme were calculated from the Ki values. In addition, by using these −ΔGbind values the values of partial binding affinity, −Δg for the several atoms and atomic groups or the several moieties contained in the polyoxin J molecule were estimated. From the results obtained, it was concluded that the carbamoylpolyoxamic acid moiety of polyoxins helps to stabilize the polyoxin-enzyme complex through the contributions of its oxygen atom at C−1″, amino group at C−2″, hydroxyl groups at C−3″ and C−4″, aliphatic carbon chain and terminal carbamoyloxy group. The results obtained by the kinetic investigation using various nucleotides and nucleotide sugars suggested that there was a specific binding site on the enzyme corresponding to the uridine moiety of UDP-N-acetylglucosamine, and that the pyrimidine nucleoside moiety of polyoxins was also bound to this site.

トリシクラゾール, CGA 49104, フサライドなどの非殺菌性抗いもち剤が, いもち病菌菌糸によるメラニン合成を阻害し, 培地中に中間体やその代謝物を蓄積することはすでに知られているが, これらの薬剤に最も感受性の高い感染過程において重要な働きをする付着器の成熟過程でも同様に2-ヒドロキシジュグロン (2-HJ) 等の蓄積が認められた. セロファン膜への穿入も同時に阻害されるが, 菌糸によるセルラーゼの産生に対する影響はなく, メラニン生合成後期中間体の薬剤との拮抗作用も完全でないことから, 2-HJのような細胞毒性を有する代謝物が付着器内およびその近傍に蓄積することが, 菌の感染機能の獲得または発現を阻害する一要因であることを推定した.

The substrate specificity of blasticidin S deaminase (E.C. 3.5.4.23), purified from Aspergillus terreus , has been studied in detail. The enzyme was found to catalyze the hydrolytic deamination of cytosine nucleus in blasticidin S and its derivatives, while cytosine, cytidine, cytidine monophosphate, adenosine, and guanosine were not regarded as substrates. The structural requirements of compounds for binding by the enzyme were evaluated by the nature of inhibition and inhibitor constants; deaminohydroxyblasticidin S, the reaction product, and its derivatives inhibited the enzymatic aminohydrolysis of blasticidin S competitively. The K i for deaminohydroxyblasticidin S was determined to be 2.3 × 10 −5 M , which is close to the K m for blasticidin S (2.1 × 10 −5 M ). The binding affinity of derivatives to the enzyme, −Δ G bind , was calculated on the basis of K i values, and further the partial binding affinities, −Δ g , for several moieties or atomic groups in blasticidin S were deduced from the −Δ G bind values. The results showed that the enzyme involves a specific binding site with multiple points corresponding to the carboxyl group of cytosinine moiety, the amide group, and the β-amino and guanidino groups of blastidic acid moiety in blasticidin S molecule; these facts are strongly indicative of the enzyme to be a new aminohydrolase for novel nucleosides such as blasticidin S.

Glucose or sucrose enhanced germination of conidia, formation of primary appressoria and elongation of superficial hyphae, but did not induce infection by Botrytis cinerea on cucumber leaves. By enhancing conidial concentration in glucose or sucrose solution, however, B. cinerea produced significant lesions. When the conidial concentration exceeded 1×107 conidia/ml in 5% glucose or 5% sucrose solution, inoculated conidia fused with each other and formed netted structures on cucumber leaves. Similar fusions were also reported in the process of infection by Fusarium nivale. Hyphae growing out from the netted structures were more vigorous than hyphae or germ tube from single conidia. The hyphae from the structures formed appressoria, which belong to the second type of simple appressoria group. From the appressoria, infection pegs developed through epidermal cell walls. In 24hr after inoculation, infection hyphae were observed in the epidermal cells, and also in mesophyll cells 48hr after inoculation. It seems that glucose induces the conidial fusion and formation of the netted structures under the condition of more than a given concentration of conidia. The netted structures are thought to play a role of supplying nutrients for the infection by B. cinerea.

Several cationic surfactants were tested for their inhibitory activities against powdery mildew of cucumber. Among alkyltrimethylammonium chloride, the octyl derivative was the most effective on the powdery mildew, but caused a little phytotoxicity. Alkyldimethylbenzylammonium chloride used in this experiment showed low effects. Didodecyldimethylammonium bromide was remarkably effective, and caused on phytotoxicity on cucumber plants. Inhibitory effects of didodecyldimethylammonium bromide were observed at various growth stages of the cucumber powdery mildew fungus (Sphaerotheca fuliginea), namely, conidial germination, appressorial formation, haustorial formation, hyphal growth, and sporulation. The compound was effective on the fungus at all stages of the life cycle, especially at haustorial formation, hyphal growth, and sporulation. Also the stained mycelia of this fungus showed a speckled, collapsed membrane system and death of hyphal cell were observed frequently. These results suggest that didodecyldimethylammonium bromide act on the cell membrane.

1-メチルチオセミカルバジドは田面水中に施用されたのち, 湛水土壌系中において抗菌性物質を含む三つの化合物に変換し, 抗菌性物質と他の1成分はイネ体内に吸収された. 抗菌性物質はイネ体内で長期にわたり保持されるところから, 1-メチルチオセミカルバジドの田面水中施用によるすぐれたイネ白葉枯病防除効果は, 本抗菌性物質によるものと考えられる. 抗菌性物質をイネ体より抽出精製し同定したところ, 2-アミノ-1,3,4-チアジゾールであった.

Purine-related compounds, cyclic AMP, 5'-AMP, 5'-IMP, adenosine and inosine, induced formation of secondary appressoria of Botrytis cinerea on slide glass in the presence of glucose. Among these purine-related compounds, formation of the secondary appressoria was remarkable in inosine. Formycin B, which is an analogue to inosine, reduced inductive effects of the secondary appressoria with inosine, and competed with inosine in forming the secondary appressoria. The administration of inosine to mycelia of B. cinerea resulted in an increase of syntheses of both DNA and RNA, followed by an increase of protein synthesis. When the mycelia incorporated 14C-inosine were fractionated, radioactivity was detected in RNA fraction at early time after incubation, and afterward in DNA fraction. Formycin B did not inhibit biosynthesis of cellular macromolecules in the mycelia, but inhibited DNA synthesis stimulated with inosine. It was shown that formycin B competed with inosine for DNA synthesis. These results indicated that inosine stimulated DNA synthesis, followed by an increase in RNA and protein syntheses in the mycelia, resulting in induction of the secondary appressoria.

キュウリうどんこ病菌 Sphaerotheca fuliginea を供試し, 本菌の生育過程に及ぼす大豆レシチンの影響を検討した. キュウリ子葉裏面に大豆レシチン2000ppmを処理し, うどんこ病菌分生胞子を接種し, 分生胞子の発芽, 菌糸の伸長, 分生子梗, 分生胞子の形成を経時的に走査電顕により観察した. 分生胞子の発芽には著しい抑制はみられなかったが, 無処理区に比し, 発芽管がやや太く, 短くなり, 菌糸の伸長が遅くなる傾向がみられた. もっとも顕著な影響は, 処理区の接種3日目以降の菌糸先端部に現われた. すなわち, 伸長した菌糸の先端部周縁に薄膜が見られ, うなぎ尾状を呈し, 日数の経過とともに膜の部分が拡大することであった. また無処理区に比し, 分生子梗, 分生胞子の形成が遅れ, 数も少なく, とくに分生胞子が分生子鎖から離脱せずに, そのままたれ下がり, 全体的にゼンマイ状を呈するものがみられた.

The formation of conidiophores and conidia were observed under an optical and scanning electron microscope. Leveillula taurica is one of a few endophytic species of powdery mildew. From inoculation to the emergence of fungus through stomata, it takes 3 days in summer and 7 days in winter. However, it was found in our experiments that this fungus was not only endoparasitic, but that it also had a creeping habit on the surface of pepper plants to form conidiophores on superficial mycelia (8%). Conidia were formed within 20 hours of conidiophore formation. Primary and secondary conidia differed markedly: primary conidia were boat-like in shape while secondary conidia were elliptical. The conidia were about 130×30μm in size, with thorn-like projections on the surface. Such projections were also recognized on the surface of conidiophores, on which they were concentrated on about the upper two-thirds of the surface below the conidia. They gradually thinned out and none were found on the conidiophore-base. This thorn-like projection on conidia and conidiophores is one of the features of L. taurica. Several kinds of exophytic species, Sphaerotheca fuliginea, Erysiphe graminis, Cystotheca lanestris and Oidium euonymi-japonicae do not have such thorn-like projections either on their conidia or on their hyphae. Judging from the phenomena that conidia easily adhered to the abaxial surface of pepper leaves or a needle when they were gently attached, and in rare cases printed their traces on a slide glass when they were stirred with a needle after being attached to it, the surface of the conidia may possess some adhesive substance.

Rice blast disease preventive activities of seven amino acid derivatives were examined by using rice seedlings of the 4- or 5- leaf stage. Because N-lauroyl-L-valine (No.5) showed the most constant activity among them, it was used as the test compound in further experiments, and the following experimental results were obtained.Lauric acid, L-valine and their mixture showed lower activities than that of No.5.In comparison with activities of optical isomers of valine, no significant difference was found among them.Among various salts and esters of N-lauroyl-L-valine tested, only sodium and potassium salts were as effective as the free compound, whereas calcium salt, and methyl and ethyl esters had low preventive activity.In case of substituting other amino acids for valine residue in N-lauroyl-L-valine, L-proline, L-methionine, L-leucine and DL-alanine derivatives were as effective as No.5, whereas in case of replacing lauric acid (C12) with other fatty acids, the protective effects reduced as increasing or decreasing the number of carbon atoms of substituted fatty acids.

The epidermal cell of fruit and leaf of satsuma mandarin (Citrus unshiu), which was penetrated by the hypha of Diaporthe citri (Faw.) Wolf, granulated and turned brown in color within 1 and 2 days after inoculation. Further granulation and browning of cells occurred around the initially browned epidermal cell. A group of necrotic cells consisted of 3 to 5 cell layers was then formed in a semi-spherical shape around the initially damaged epidermal cell. Subsequently, each cell in one or two layers adjacent to the necrotic cells became a pair of cells through a cell division. The cell division was repeated to make up a callus consisting of 10 to 12 cell layers around the necrotic cells. Thereafter, periderm was formed between the necrotic cells and the callus. Thus the melanose spot was finally formed by the three parts of a group of necrotic cells, a callus and a periderm, and invaded tissue was demarcated histologically. This phenomenon means self-protecting reaction responsed to the stimulation of citrus epidermal cell with penetration of D. citri, and melanose spot was formed as a mechanical barricade tissue by the self-protecting reaction. Star melanose and scar developed also in a similar fashion to that of melanose spot, consisting of a group of necrotic cells, a callus and a periderm. It seems that the self-protecting reaction started by response to the local damages resulting in dead cells of citrus by penetration of pathogens, permeation of drugs and mechanical injurys.

A series of experiments were conducted to clarify the reason why the invading hyphae of Diaporthe citri (Faw.) Wolf is arrested and killed in melanose spot. After a melanose spot on citrus leaf was formed, pycnospore suspension of D. citri with 2% fructose was inoculated onto the melanose spot. The pycnospore germination was markedly inhibited and the germination rate was only 7%. On the healthy part of the leaf, the germination rate was 98%. The extract of melanose spot inhibited the pycnospore germination of D. citri. An antifungal substance was isolated from the extract of melanose spots by the chromatography on silica gel G layer. It was then crystallized from acetone-water, and needle-like crystal was obtained and named inhibitor D. Inhibitor D was not detected on the chromatogram of the extract of uninfected leaves and peels of citrus plant. It means that inhibitor D was produced in the plant post infectionally, and may be a phytoalexin. The extract of uninfected leaf also inhibited the pycnospore germination of D. citri. It seems that the inhibitory effect of the extract of uninfected leaf is caused by the action of pre-inhibitins such as citrinol, naringin and hesperidin in the uninfected tissues of citrus plant. These results explain the reason why the invading hyphae of D. citri into the citrus leaf and peel was arrested and then killed; namely, it is due to the antifungal action of pre-inhibitins and the phytoalexin-like substance. Therefore, this phenomenon seems to be a chemical defense reaction in citrus plant against invasion of pathogenic fungus. The phytoalexinlike substance was also detected from scab spot, canker spot, star melanose and oleocellosis on citrus fruits.

An extract of cultured Agroxieinma githago L. cells was found to show potent inhibitory activity against plans virus infection. The effects of cultural conditions on the growth of the cell suspension and on the production of the inhibitor were examined. Since the production of substance was dependent on growth. experiments were made to improve growth. The optimum temperature was 26 to 30°C and optimum pH of the medium before autoclaving was between 5 and 7. In a medium of higher osmotic pressure, the water content of the cultured cells was lowered markedly. The growth rate in a small volume of the medium was higher than that in a larger volume at an early stage of the cultivation, but it was not changed by different inoculum sizes. The cells required thiamine and 2,4-D for growth but no other vitamins or growth regulators. The optimum level of 2,4-D was 0.1 mg/l. Higher sucrose concentration in the medium gave higher production of cell mass and of the inhibitor. However, 3% of sucrose was selected as the most economical concentration. For normal cell growth, the presence of both NH4NO3 and KNO3 as nitrogen sources was required. The use of a single nitrogen source caused a long lag period or inhibition of the cell growth. KH2PO4 stimulated the growth when in was used in the level of 2.5 to 5 mM. The cell adhesion on the surface of the fermentor sometimes causes trouble in a large-scale cultivation. It was found that reducing the Ca2+ level in the medium prevented the cell adhesion and foaming remarkably. Based on the results obtained, a modified medium was established which was excellent for shortening the culture period and for efficient production of the anti-plant virus inhibitor.

フサライドを実験室で調製した堆肥に添加しその代謝過程を検討し, 生成した代謝産物について若干の生理作用を検討した.(1) フサライドは, 堆肥中ですみやかに代謝された. 代謝産物としてベンゼンおよび酢酸エチル区分から18種の化合物が同定されたが, 時間とともに水層区分の増加が認められた.(2) フサライドは堆肥中で開環し, 3, 4, 5, 6-テトラクロロ-2-ヒドロキシメチル安息香酸塩として存在していた. このように水溶性の大きい型をとりうる性質はその後の代謝をうけやすく, 残留性の大きい塩素系殺虫剤と異なるところであると考えられる.(3) 代謝過程はまずテトラクロロフタル酸への酸化である. 次に核塩素のSCH3化であり, おもに 4, 6, 7-トリクロロ-5-メチルチオフタリドが生成し, またこの化合物の代謝では酸化生成物のフタル酸誘導体のみ認められ, この生成機構に関しても推論した.(4) クロロフタリドの脱塩素化は5位, 6位の順に起こり7位塩素の脱離は前者に比較し遅かった. またクロロフタル酸の脱塩素化は3位, 6位が非常に速く, 4位, 5位塩素の脱離は遅くなっていた.(5) すべての代謝産物はフサライドより水によく溶け, 残留性や蓄積性の少ない化合物に変化してゆくことが予想された. また野菜に対する薬害はフサライドより若干強い代謝産物があったが, その生成量が少ないことから実際の場面で薬害を起こすことはないものと考えられる.

キュウリ斑点性細菌病菌を用いてマイオマイシンの作用機構について検討した. 本抗生物質は増殖中期の供試菌の増殖を10μg/mlの濃度で完全に阻害した. ピルビン酸, 酢酸を基質とする呼吸は阻害されたが, グルコース,クエン酸, コハク酸の場合は阻害されなかった. 呼吸阻害についてはマイオマイシン耐性菌においても同様の結果が得られた. また, 放射性前駆体を用いての取り込み実験では, あらかじめ取り込ませた細胞からの放射性物質の漏出はみられず, 14C-ウリジン, 14C-チミジン, 14C-グルコサミン, 14C-酢酸の取り込みは阻害されなかったが, タンパクへの14C-フェニルアラニンの取り込みは強く阻害された. なお, 耐性菌においては, 14C-フェニルアラニンの取り込みはほとんど阻害されなかった. 以上の結果から, 本抗生物質はタンパク合成に強く作用しているものと思われる.

Various derivatives of polyoxin C, other polyoxins and several uridine analogues have been known as competitive inhibitors of chitin-UDP acetylglucosaminyitransferase (EC 2.4.1.16, chitin synthetase). Their inhibitory activities were more or less dependent on pH. The variation of inhibitor constants Ki or Michaelis-Menten parameters Km and V with pH was investigated and the data obtained were plotted according to the method proposed by Dixon et al. From the results of the pKi-pH plots for the above competitive inhibitors, it was concluded that the ionized amino group at C−2″ position acted a very important role for the binding of polyoxins to chitin synthetase. The carbonyl oxygen atoms at C−1″ and of the carbamoyloxy group probably participated in the hydrogen bond formation with the enzyme. And pH scarcely influenced on the interaction between the carboxyl group at C−5″ and the enzyme. The results of the Dixon plots for variations of Km and V with pH suggested that an unionized imidazole group (pKa = 6.3) and an ionized amino group (pKa = 7.7) of chitin synthetase were concerned in the enzyme reaction.

Purine and their relative compounds were found to accelerate the infection and lesion formation caused by gray mold fungus, Botrytis cinerea, on cucumber seedling in the presence of glucose at the concentration more than 2.5%. The required concentration of all these compounds for exhibiting their action on the gray mold fungus to accelerated the infection and lesion formation were more than 1×10-5M. All pyrimidines, however, were not effective, even at the concentration of 1×10-3M. Among the purines, the tri- and the mono-phosphates were much more effective; whereas the free bases and the diphosphates were somewhat less effective. Some metabolites of purines, uric acid, allantoin and allantoic acid were considerably effective as well as that of ATP and AMP.

A large number of strains of Alternaria kikuchiana that cause the black spot disease on pear were isolated from some orchards of Tottori Prefecture, Japan. From them seven strains, which showed different sensitivities to polyoxin B, were selected and used in the experiments. Polyoxin B, at a concentration of 10μM, inhibited more than 50% of the incorporation of glucosamine-14C into cell-wall chitin in washed mycelia of the polyoxin-sensitive strains and at the same time resulted in an unusually increased accumulation of UDP-N-acetylglucosamine-14C, which is a precursor of chitin biosynthesis. Both the inhibition of glucosamine-14C incorporation into chitin and the increase of accumulation of UDP-N-acetylglucosamine-14C caused by polyoxin B were moderately lowered with decreasing the sensitivity to the antibiotic of the different strains. Crude preparations of chitin synthetase were obtained from these strains. Polyoxin B strongly inhibited all the enzyme preparations in competition with their substrate UDP-N-acetyl-glucosamine. The Km values for the substrate or the Ki values for the antibiotic determined in the enzyme reactions differed slightly from each other. These results indicate that polyoxin B acts as an competitive inhibitor of chitin synthetase, which is concerned in the synthesis of cell-wall chitin of A. kikuchiana. And they also suggest that the polyoxin-resistance of this fungus is caused by a lowered penetration of the antibiotic through the cell membrane into the enzyme site.

Blasticidin S deaminase (EC 3.5.4.23) was purified by affinity chromatography using a column of Sepharose 4B coupled with pyrimidinoblasticidin S as a ligand. The Michaelis constant Km and the maximum velocity Vmax varied with pH, which suggests that enzyme ionization is important either for substrate binding or for catalytic activity. The inflection point at pH 8.6-8.9 in the plot of pKm versus pH was attributed to an enzyme amino group which corresponded to the carboxyl group of substrates, and an inflection at pH 5.3 in the log Vmax-pH plot was assigned to the imidazole group of histidine, which appeared to be critical for catalytic deaminohydroxylation. The binding of substrates by the enzyme was inferred to be promoted thermodynamically, and activation of the substrate-enzyme complex was presumed to proceed endothermically. From the results obtained, a hypothetical mode of reaction for blasticidin S deaminase is proposed.

殺菌性抗いもち剤およびプロベナゾールは, いもち病菌の色素合成 (黒色化) に影響を与えなかったが, トリシクラゾール, CGA 49104, フサライド, ペンタクロロベンジルアルコール (PCBA) は菌系によるポリケタイド系のメラニン生合成を阻害または攪乱し, 中間体: シタロンおよび代謝物: 2-ヒドロキシジュグロン (2-HJ, 黄色色素) を共通に蓄積した. ただ, フサライドとPCBAはフラビオリン赤色色素の蓄積にはあまり影響しなかった. これら薬剤のセロハン膜法による付着器からの侵入阻害は葉鞘検定の結果とよく一致し, 薬剤の一次作用点が宿主側よりは菌側にあることを示唆した. また,これら薬剤は, いもち病菌付着器の黒化も抑制するが, トリシクラゾール, CGA 49104の存在下にメラニン合成の後期中間体: バーメロンまたは1,8-ジヒドロキシナフタレンを添加すると, 付着器からセロハン膜への穿入回復は明瞭でなかったものの, 着色阻害は完全に回復した. 一方, 2-HJとシタロンは, いもち病菌の感染過程に影響することが認められ, メラニン合成阻害に基づく付着器の未熟に加えて生理活性中間体の蓄積も薬剤の有効性に関与している可能性が考えられた.

抗性物質マイオマイシンは1973年に, French らにより発見されたものであるが, 植物病原菌に対する効果については報告されていないので, 7種の植物病原細菌を用いて試験し, 寒天希釈法で, 25～100μg/ml濃度, 比濁法では, 2～100μg/ml濃度で各細菌の生育を完全に阻害した. しかし, 寒天拡散法では100μg/ml濃度でも非常に小さな阻止円しか形成されなかった. 一方, in vivo 試験においては, ハクサイ軟腐病およびキュウリ斑点細菌病に対し, 45～75μg/ml濃度で顕著な防除効果が示された. さらに, ストレプトマイシン耐性株によるキュウリ斑点細菌病に対しても, かなりの防除効果を有することが認められた.

Rice seedlings grown from seeds that had been soaked in dodecyl DL-alaninate hydrochloride (AH) solution were found to be resistant to infection by the rice blast fungus, Pyricularia oryzae.1. Number of lesions was fewer on rice seedlings grown from AH-soaked seeds than on seedlings grown from the water-soaked seeds.2. Resistance to infection increased as concentration of AH was increased up to 500ppm. Concentrations above the optimum caused a decrease in the preventive value of the treatment.3. Resistance was most effectively induced when seeds were soaked in AH solution for 72 hours.4. No significant resistance was induced in seedlings for first 20 days under a glasshouse condition. Resistance then increased and the maximum inhibition of disease development was attained at about 30 days. This induced resistance was retained without decrease for 75 days.

The previous studies made on the mode of action of sodium dimethyldithiocarbamate (NaDMDC) showed that the compound inhibited the lipid synthesis of Xanthomonas oryzae, but not the process from long-chain fatty acids to phospholipids in the biosynthetic pathway of lipids. Further examinations were made on the effects of NaDMDC on the process from acetate to fatty acid formation. NaDMDC inhibited neither the two kinds of enzymes involving in the formation of acetyl CoA from acetate, acetate kinase and phosphotransacetylase, nor the enzyme concerning in the synthesis of malonyl CoA from acetyl CoA, acetyl CoA carboxylase. However, the compound had a high inhibitory effect on the incorporation of 14C-malonyl CoA into fatty acids, in either the fatty acid-synthesizing enzyme system of Escherichia coli or the cellfree extracts of X. oryzae.From these results, it is concluded that NaDMDC inhibits primarily the fatty acid synthesis of X. oryzae, and gives a remarkable influence upon the entire lipid biosynthesis.

The formation of conidiophores and conidia were observed under an optical and scanning electron microscope. Leveillula taurica is one of a few endophytic species of powdery mildew. From inoculation to the emergence of fungus through stomata, it takes 3 days in summer and 7 days in winter. However, it was found in our experiments that this fungus was not only endoparasitic, but that it also had a creeping habit on the surface of pepper plants to form conidiophores on superficial mycelia (8%). Conidia were formed within 20 hours of conidiophore formation. Primary and secondary conidia differed markedly: primary conidia were boat-like in shape while secondary conidia were elliptical. The conidia were about 130×30μm in size, with thorn-like projections on the surface. Such projections were also recognized on the surface of conidiophores, on which they were concentrated on about the upper two-thirds of the surface below the conidia. They gradually thinned out and none were found on the conidiophore-base. This thorn-like projection on conidia and conidiophores is one of the features of L. taurica. Several kinds of exophytic species, Sphaerotheca fuliginea, Erysiphe graminis, Cystotheca lanestris and Oidium euonymi-japonicae do not have such thorn-like projections either on their conidia or on their hyphae. Judging from the phenomena that conidia easily adhered to the abaxial surface of pepper leaves or a needle when they were gently attached, and in rare cases printed their traces on a slide glass when they were stirred with a needle after being attached to it, the surface of the conidia may possess some adhesive substance.

炭酸水素ナトリウムのカンキツ貯蔵病害に対する効果を付傷接種および普通貯蔵において検討し, 以下のような結果を得た.果実を0.25Mの炭酸水素ナトリウム溶液中に浸漬したのち付傷し, P. digitatum の胞子を接種した場合, 本菌による緑カビ病はまったく発生しなかった. thiophanate の700ppm溶液に浸漬した場合には, 21%の果実に緑カビ病の発生がみられた. また, 果実に付傷したのち薬液に浸漬し, 接種した場合, 炭酸水素ナトリウム区では緑カビ病はまったく発病しなかったが, thiophanate 区では11%の果実に緑カビ病が発生した. 果実に付傷後, 接種し, 24時間湿室に保ち感染させたのち, 薬液に浸漬した場合, 炭酸水素ナトリウム区では緑カビ病の発生が68%抑制された. thiophanate 区では18%の抑制であった. また, 炭酸水素ナトリウムは thiophanate には及ばなかったが, P. itaricum による青カビ病の発生をも抑制した. さらに, 5週間にわたる常温貯蔵において, 炭酸水素ナトリウムは緑カビ病の発生をほとんど完全に抑制した. thiophanate 区では約25%, 無処理区では約50%の果実に緑カビ病が発生した. 炭酸水素ナトリウムは緑カビ病以外の貯蔵病害 (軸腐れ病, 黒腐れ病など) の発生をも抑制し, thiophanate 区よりもまさった.

炭酸水素ナトリウム (SBC) はカンキツ緑かび病をはじめ数種の植物病害に抑制効果を有するが, 植物体上で結晶化し, 効果にふれがある. 食添用乳化剤を加えて製剤化した結果, キュウリ, ナス, イチゴなどのうどんこ病防除薬剤として実用性のあることが判定された. 本剤の作用特性を知る目的で, キュウリうどんこ病菌 Sphaerotheca fuliginea の各生育過程に及ぼす影響を検討し, 次のような結果が得られた. 1) 直接SBC剤2,000ppmを散布することによって, 分生胞子発芽の80～100%を阻害した. 2) 菌糸伸長には水処理と大差はなく, 強い阻害効果は認められない. 3) 分生子梗形成の抑制率は38%であって, あまり抑制的ではなかった. 4) 分生胞子形成は約20時間で無処理1分生子梗あたり5個であったが, SBC剤処理区ではまったく形成されなかった. 5) 新生分生胞子にSBC剤を処理したところ, 表面に小突起ができ, わずかな圧力で細胞壁が破れ, 内容物がとび出した. このような分生胞子を接種しても発病にいたらず, そのうえ, SBC剤は分生胞子の飛散を著しく抑制した.