Volatile fungicidal substances, which affect the survival of Fusarium oxysporum f. sp. raphani in soil flooded with 3% glucose solution in vitro, were analysed by using a cryogenic trap, by bioassay, gas chromatography and gas chromatography-mass spectrometry. The antifungal volatile substances collected consisted of two components: acetic acid and n-butyric acid. Their concentrations in the centrifuged supernatant of the soil were 3, 407 and 2, 944 ppm, respectively, when the fungicidal activity in the soil reached maximum values on the 6th day after flooding. The concentrations were high enough to kill the chlamydospores of the fungus. Other volatile substances including hydrogen sulfide were not related to the fungicidal activity of the soil. These results suggest that the fungicidal activity of glucose-amended flooded soil was associated with the production of acetic acid and n-butyric acid in the soil.

View full abstract

Host range of Polymyxa sp. isolated from various plants grown in rhizomania-infested soils of three different localities in Hokkaido was compared. Among 108 species of plants belonging to 23 families tested, 12 plants belonging to Chenopodiaceae, Amaranthaceae and Portulacaceae were infected with the fungus. The other 20 families including Gramineae were not infected. All isolates of Polymyxa sp. were identified as Polymyxa betae Keskin on the basis of their host range and morphological characteristics. The host range of the isolates was found to be limited to the family of the original host. Among the Chenopodiaceous isolates, that from sugar beet did not infect Chenopodium album, and those from C. album did not infect sugar beet. These P. betae isolates could be divided into several formae speciales; Amaranthus retroflexus isolates were identified as P. betae Keskin f. sp. amaranthi Barr, for the Portulaca oleracea isolates a new forma specialis P. betae Keskin f. sp. portulacae was proposed. Although sugar beet isolates and C. album isolates should be divided into different formae speciales, respectively, the classification of these isolates should await comparison with the Canadian isolate from C. album. From these results it is suggested that sugar beet isolates of P. betae which have a high infectivity to Beta vulgaris are associated with the incidence of rhizomania of sugar beet whereas the other two formae speciales and C. album isolates may not be involved.

View full abstract

The zonate leaf spot fungus newly found on mulberry, Morus alba, in Japan since 1978 was identified as Gonatophragmium mori (Sawada) Deighton (=Spondylocladium mori Sawada). Many new host plants, being 28 species belonging to 24 genera of 16 families, were recorded through the field surveys around mulberry plantations. In the overwintering experiments with naturally or artificially infected leaves on Morus, Vitis and Broussonetia, development of teleomorph, the perfect state was confirmed. Ascospores serve as the primary infection source in early summer. From the pathogenicity to Morus and Vitis with ascospores and conidia, and the identity of morphological characteristics of perithecial and anamorph, conidial states, the causal fungus was re-classified as Acrospermum viticola Ikata apud Ikata and Hitomi (1931) having the conidial state, Gonatophragmium mori (Sawada) Deighton (1969).

View full abstract

Occurrence of hairy root has been detected on roses in Shizuoka prefecture since 1979. The causal bacterium was isolated from the rootlets of Floribunda rose, Hybrid tea rose and Climbing rose, and was tested for its pathological and bacteriological characteristics. Eighteen isolates were identified as Agrobacterium rhizogenes based on their pathological traits as well as 82 cultural, physiological and biochemical properties. These isolates were differentiated into two biovars due to the differences in the following characteristics: 3-ketolactose production, Kovac's oxidase, H₂S production, arginine dihydrolase, ferric ammonium citrate test, nitrate reduction, nitrate respiration, acid production from raffinose. ethanol and erythritol, utilization of L-tyrosine, malonate and tartrate, litmus milk reaction, growth factor requirement, growth at 35 C, growth in 2% NaCl pepton water, growth on Schroth et al. medium, New and Kerr medium, calcium glycerophosphate agar, sodium selenite agar, Starr's basal medium, congo red mannitol agar and aniline blue mannitol agar, and growth in a synthetic medium with asparagine and ammonium salts as a sole source of C and N. Seven isolates were classified as biovar 1, and other 11 isolates as biovar 2. The virulence of these isolates to rose and tomato were stronger than that to carrot. The GC contents determined by HPLC method were in the range of 58.7-60.7%.

View full abstract

Cycas necrotic stunt virus (CNSV; considered to belong to nepovirus group) isolated from cycad plants was characterized further. The sedimentation coefficients of the components M (middle) and B (bottom) were 85S and 112S, and buoyant densities in CsCl were 1.404 and 1.472 g/cm³, respectively. When the infectivity of the components was tested, the mixture of both components was five to twenty times more infectious than either particle alone. M and B components contained single-stranded RNA species with molecular weight (MW) of 1.5×10⁶ (RNA2) and 2.5×10⁶ (RNA1), respectively. Both RNA1 and RNA2 were necessary for infection. M and B components contained a single major polypeptide with identical MW of 65 K. These properties of virus particles, nucleic acid and coat protein of CNSV confirmed affinities of CNSV to nepoviruses, particularly to tomato black ring virus (TBRV). However, since no serological relationship between CNSV and TBRV or serologically TBRV-related viruses was detected in our previous work, CNSV would be a new nepovirus having similarities to TBRV in biochemical properties.

View full abstract

Chemically characterized pure host-specific toxins produced by Alternaria alternata strawberry pathotype (AF-toxins) were examined for their biological activities. AF-toxin I induced even at concentrations as low as 3.2×10^-8M leaf veinal necrosis on both leaves of susceptible cv. Morioka 16 of strawberry and cv. Nijisseiki of Japanese pear. AF-toxin II was found to cause veinal necrosis only on leaves of the susceptible Japanese pear cv. Nijisseiki with a minimum concentration of 2.6×10^-8M. AF-toxin III was toxic to susceptible strawberry leaves at 3.1×10^-7M, and also toxic to Nijisseiki pear leaves at considerable high concentrations more than 1.6×10^-5M. At concentrations up to 10^-4M, there was no effect observed in any of the experiments with the strawberry cv. Hoko-wase and Japanese pear cv. Chojuro, immune to the disease. We also examined the ability of AF-toxin II to protect strawberry leaf tissues from AF-toxin I action and fungal infection. Detached leaves were exposed to AF-toxin II for 18hr, and then treated with AF-toxin I. AF-toxin II gave a remarkable protection against AF-toxin I-induced veinal necrosis and potassium leakage. Minimum ratio of AF-toxin II: AF-toxin I giving 80% protection was approximately 10:1. Pre-treatment with AF-toxin II reduced significantly the number of black necrotic spots on inoculated susceptible cv. Morioka-16 of strawberry. The present experiment provided the first evidence of protecting plant from disease by means of counteracting toxin action by a chemical structurally related to the host-specific toxin.

View full abstract

Three rhabdovirus isolates (R, H and S) from strawberry were studied for symptoms on indicator plants (Fragaria vesca UC-4, UC-5 and UC-6 and F. virginiana UC-10, UC-11 and UC-12). On the basis of the characteristics of reactions and symptoms on indicator plants. isolate R was classified as a typical strawberry crinkle virus (SCrV), and isolates H and S as typical strawberry latent C virus (SLCV). Electron microscopy of cells infected with the above three isolates and SLCV maintained in Oregon State University (SLCV-0) revealed the presence of rhabdoviruslike particles of about the same size, and viroplasms for all isolates. In cells infected with the isolate R, virus particles and viroplasms were consistently observed to accumulate in the cytoplasm. In contrast, cells infected with isolates H. S and SLCV-O appeared to contain mature particles predominantly in the perinuclear space and immature particles and viroplasms in the nuclei. These findings indicate the evidence of two distinct rhabdoviruses in strawberry; one is the cytoplasm-associated SCrV and the other is the nucleus-associated SLCV.

View full abstract

Behavior of Zygophiala jamaicensis Mason on grape berries (Vitis vinifera L. cv. ‘Muscut of Alexandria’ and cv. ‘Neo Muscut’) was investigated by optical microscopy. On the surface of berries, a pair of two-celled conidia were usually found to attach to bloom. The evanescence of bloom occurred around ungerminated conidia, being 5-15μm wide. A germ tube usually emerged from each cell of conidium. Bloom along germ tubes and hyphae evanesced probably by a degenerating enzyme(s) secreted from them. The width of bloom-evanescing zone increased with growth of hyphae. The evanescing zone formed by paired conidia fused with that by other neighbouring conidia, forming a visible symptom area. Conidia produced on the bloom-evanescing zone seemed to be detached soon after produced. At a later stage of infection, superficial hyphae on the bloom-evanescing zone formed mycelial networks and a great number of thick, dark-colored hyphae gathered, finally to form a black microsclerotium-like structure on the berry surface. Observation of sections of paraffin-embedded specimens revealed that this structure developed on the cuticular surface and that any fungal structures were not found in fruit tissues including epidermis. These observations suggested that Z. jamaicensis could be an ectoparasite which lives on bloom on grape berries. The visible symptom was perhaps ascribed to action of enzyme(s) secreted by this fungus.

View full abstract

Chinese yam necrotic mosaic virus (CYNMV) was purified from naturally infected chinese yam leaves by repeated differential centrifugation. The molecular weight of the capsid protein was determined as 38, 000 (38K) with SDS-polyacrylamide gel electrophoresis. The antiserum produced against purified CYNMV preparation had a titer of 1:4, 096 as determined by immunosorbent electron microscopy and was used for the detection of the 38K polypeptide from leaf homogenate by electro-blot immunoassay. The procedure was simplified to complete all the steps within 7 hours. The 38K polypeptide was readily detected from diseased leaf homogenate diluted up to 1/1, 000 but not from healthy leaf homogenate. Reaction with host plant proteins was reduced by diluting the antiserum up to 1/5, 000 without losing sensitivity to CYNMV capsid protein.

View full abstract

The production of ethylene in primary leaves of oat following inoculation with uredospores of Puccinia coronata f. sp. avenae was studied. Leaves of cv. Shokan 1 exhibited two distinct peaks of ethylene production at 8 hr and 35 hr after inoculation with incompatible race 226, while the leaves inoculated with compatible race 203 exhibited only one peak at 8 hr. Causal relationship between the increase of ethylene level and resistance expression was examined by the blockage experiments of resistance using NaN₃, CoCl₂, diethyldithiocarbamic acid, 2, 4-dinitrophenol, salicylhydroxamic acid, propyl gallate, cordycepin and blasticidin S or by the double inoculation technique. The results indicated that the ethylene production is not responsible for the limitation of fungal development. Exogenous supply of ethylene and its precursor, 1-aminocyclopropane-carboxylic acid, had no effect on uredosorus formation on susceptible Pc cultivars. It was suggested that enhanced synthesis of ethylene would not be a causal event but rather be a part of spurious phenomena associated with resistance response.

View full abstract

Grape berries infected by the flyspeck disease, were observed by scanning electron microscopy. The bloom covering the surface of healthy berry consisted of crystalline structure of flake-like appearance. This structure around attaching conidia and growing hyphae of Zygophiala jamaicensis Mason, a causal fungus, has been degenerated probably by enzyme (s) secreted by this fungus and changed into a thin film. Most of hyphae were found to grow underneath such a film. The crystalline structure around apices of growing hyphae remained unaltered but that along the hyphal region 10-15μm and more behind the apex appeared to be altered, suggesting that the bloom-degenerating enzyme (s) might be secreted from the latter region but not apex. The microsclerotium-like structure formed on the bloom-evanescing regions of berry seemed to be formed by a great number of branching hyphae emerged from several, thick hyphae. Micromanipulation at the scanning electron microscope level revealed that the central region of microsclerotium-like structure consisted of 3-4 hyphal layers and the marginal region 2-3 layers. This technique also revealed that there were no fungal structures penetrating cell walls of the berry. These observations support our earlier result by light microscopy that the present causal fungus might be an ectoparasite which lives on the bloom of grape berries.

View full abstract

We tried to apply the onion epidermal strip method for the observation of conidial germination, hyphal elongation and hyphal penetration of Botrytris cinerea. The behavior of the fungus on the strip was compared with that on a petal of Primula polyantha, the natural host plant. The similar tendency was observed on the conidial germination and hyphal penetration on both system. In addition, each stage on the onion epidermal strip was markedly accelerated by the addition of 1 to 2% fructose to the conidial suspension. It was suggested that the onion epidermal strip method might be applicable for assaying the effect of chemicals on B. cinerea.

View full abstract

Bacterial shoot blight of tea caused by Pseudomonas syringae pv. theae is a disease which attacks several cultivars including Inzatsu 131 producing deep brown necrotic lesions on leaf blades, petioles and stems. In July 1983, however, new symptoms were detected on the undersurface of the leaves of cv. Yabukita in Shizuoka Prefecture. They were characterized by light brown and shallow necrosis limited to the lower epidermis and a few layers of subepidermal spongy parenchyma cells. The causal bacterium was identified as P. syringae pv. theae. The results of inoculation tests at different temperatures suggested that this bacterium induces diverse symptoms on tea leaves depending on the climatic conditions as well as the kinds of cultivars.

View full abstract

[in Japanese]

View full abstract

[in Japanese]

View full abstract

[in Japanese]

View full abstract

[in Japanese]

View full abstract