Japanese Journal of Phytopathology
Online ISSN : 1882-0484
Print ISSN : 0031-9473
ISSN-L : 0031-9473
Volume 60 , Issue 6
Showing 1-18 articles out of 18 articles from the selected issue
  • Taketo UEHARA, Daijiro HOSOKAWA
    1994 Volume 60 Issue 6 Pages 649-657
    Published: December 25, 1994
    Released: February 19, 2009
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    The distribution of virus RNA molecules in tobacco mosaic virus (TMV) infected tobacco protoplasts was examined with time after inoculation using in situ hybridization with strand specific riboprobe labeled with digoxigenin. Analysis of hybridization signals for TMV plus strand RNAs showed very weak signals throughout the cytoplasm of the protoplasts sampled at 2hr post-inoculation (p.i.). Thereafter, intensity of the signals increased in the cytoplasm and reached a maximum level at 12hr p.i. There was then a rapid decrease in the intensity of signals. Weak signals in the in situ hybridization using a minus strand specific probe also were first observed at 2hr p.i. The intensity of signals, then increased and gradually decreased after a maximum level at 12hr p.i. Intensity of the signals at a maximum level, however, was much less than that of plus strand viral RNA. No hybridization signals for plus strand RNAs or minus strand RNAs was demonstrated in the nucleus throughout the period of infection. These results strongly indicated that the site of replication of TMV-RNA is the cytoplasm and that the nucleus is not directly associated with its synthesis.
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  • Kenji TAKAHASHI
    1994 Volume 60 Issue 6 Pages 658-666
    Published: December 25, 1994
    Released: February 19, 2009
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    Influences of environmental factors such as temperature, soil moisture and soil pH on the viability of resting spores of Plasmodiophora brassicae incubated in sterile soil were examined by using the direct method based on the fluorescent staining reaction in spores. When resting spores were incubated in acid soil, the frequency of nonviable spores increased readily and profusely after incubation and reached approximately 70 to 80% after a 30-day incubation. The rate of the increase was not appreciably affected by temperatures between 15 and 30°C and by soil moisture contents between 35 and 100% during the 30-day incubation, though affected slightly by low temperature and moisture content. The temperatures and soil moistures in the range tested were not so important factor as affecting the viability of resting spores. On the other hand, soil pH distinctly affected spore viability. A remarkable increase in the nonviable spore frequency was found in acid soils with pH values of approximately 4.5-6.5. In alkali soils the rate of increase was conspicuously low in the beginning of incubation period as compared with those in acid soils, but then the nonviable spore frequency increased continuously at an almost constant rate during a 7-month incubation. The soil pH is one of important factors affecting the viability of resting spores, but may not be the determinate factor in their survival due to lack of ability to suppress independently the decline of the viability during a long period of time.
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  • Kenji TAKAHASHI
    1994 Volume 60 Issue 6 Pages 667-674
    Published: December 25, 1994
    Released: February 19, 2009
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    Viability of the resting spores of Plasmodiophora brassicae incubated in natural and autoclave-sterilized soils without host roots, was compared between the two soils. Although the increases of nonviable spore frequency were found in both natural and sterile soils, they were suppressed in natural soils in spite of almost the same pH values as that of the sterile soils in each test soil. The suppression in natural soils, however, varied among four test soils with an approximately optimum pH range for the frequency increase of nonviable spores. The suppression in natural soil from an uncultivated area, which was lower in populations of microorganisms, but higher in the content of total C and humus and the C/N ratio than those in the other three natural soils from fields, was less pronounced than the suppression in the others. The suppression was eliminated by gas-sterilization of natural soils. Mixtures of natural soils with sterile soils reduced the suppression. Addition of glucose in natural soils also reduced the suppression. These results suggest that the suppression of increase in the frequency of nonviable resting spores in soil is influenced by biological agents associated with the activity of microorganisms.
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  • Yoshiaki KANNO, Hisashi IIDA, Nobuyuki YOSHIKAWA, Tsuyoshi TAKAHASHI
    1994 Volume 60 Issue 6 Pages 675-680
    Published: December 25, 1994
    Released: February 19, 2009
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    Hop mosaic virus (HMV) was isolated from a mosaic-diseased hop plant (Humulus lupulus L. cv. Sunshine). The virus systemically infected two plant species, hop (cv. Shinshuwase) and Nicotiana occidentalis and only the inoculated leaves of N. clevelandii, Chenopodium quinoa, Cucurbita maxima among 24 species of 11 families. The virus was purified from infected leaves of N. occidentalis, a new host suitable for propagation of HMV. Purified virus particles were 625nm in length, 13nm in width and composed of a single coat protein species with Mr 32, 800 daltons (Da) and a nucleic acid with Mr 2.91×106 Da. In immunosorbent electron microscopy using antisera against three carlaviruses (HMV, hop latent virus: HLV and American hop mosaic virus) the virus isolated in this study reacted with an antiserum against HMV isolated in England and also weakly with antisera against HLVs isolated in Japan and England. The survey of HMV infection in commercial hop plants indicated that HMV did not occur in hop gardens in Japan though some cultivars introduced for breeding are infected with the virus.
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  • Shigeo NAITO, Seiji KANEMATSU
    1994 Volume 60 Issue 6 Pages 681-690
    Published: December 25, 1994
    Released: February 19, 2009
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    During July to August in 1992, a unusual foliar blight disease was observed on soybean plants intercropped between rows of winter wheat in an upland field converted from a paddy field at Tohoku National Agricultural Experiment Station in Morioka, northern part of Japan. The symptoms appeared as primary lesions consisting of small, circular necrotic spots, 1-mm or less than 1-mm in diameter, followed by secondary lesions showing circular to irregularly-shaped and large-sized areas of necrosis around the primary lesions under humid conditions. All the isolates of Rhizoctonia solani Kühn consistently recovered from leaves with the primary and secondary lesions (hereinafter referred to as leaf spot isolates) formed anastomoses in a high frequency (>75%) with the tester isolates of the anastomosis subgroup AG-2-1 but in a low frequency (<16%) with those of the AG-2-2 IIIB and IV and anastomosis group AG-BI. Among the 66 leaf spot isolates, 64 were auxotrophic for thiamine, whereas the isolates of the AG-2-1 were autotrophic for thiamine. The remaining 2 isolates could not grow even in the presence of thiamine. Culture appearance and optimum growth temperature of the leaf spot isolates were similar to those of the AG-2-1 rather than to those of the AG-2-2 IIIB and IV subgroup. Inoculation tests revealed that the leaf spot isolates were highly pathogenic to soybean, adzuki bean and kidney bean and caused severe pre-emergence and post-emergence damping-off, but were not pathogenic to rape and radish. The isolates caused foliar blight on soybean. These results indicated that most of the leaf spot isolates of AG-2 from soybean did not fit to either the AG-2-1 or AG-2-2 subgroup. Hence, we assigned these isolates to a new subgroup 3 in AG-2 (designated as AG-2-3).
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  • Shigeo NAKAMURA, Masanobu YOSHIKAWA, Hideharu TAIRA, Yoshio EHARA
    1994 Volume 60 Issue 6 Pages 691-693
    Published: December 25, 1994
    Released: February 19, 2009
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  • Kayo SHIRAI, Harukuni HORITA, Fumio TANAKA, Akio TANII, Yosuke MINO
    1994 Volume 60 Issue 6 Pages 694-697
    Published: December 25, 1994
    Released: February 19, 2009
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  • Toshiaki TAKEHARA, Katsuto KUNIYASU
    1994 Volume 60 Issue 6 Pages 699-704
    Published: December 25, 1994
    Released: February 19, 2009
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    Nitrate-nonutilizing mutants (nit mutants) of 11 strains of Fusarium oxysporum from various formae speciales were formed on chlorate-containing media. The nit mutants were assigned to three phenotypic classes, nit1, nit3 and NitM, on the basis of their growth on media containing one of the following five different nitrogen sources; nitrate, nitrite, hypoxanthine, ammonium and uric acid. Frequency of nit mutation and proportion of three phenotypes in the obtained nit mutants depended on the strains of each forma specialis. Each strain of 8 formae speciales used was found to belong to different vegetative compatibility group from one another by vegetative compatibility test based on complementation reaction between nit mutants on the minimal medium. It is suggested that there is a possibility to use nit mutants as a marker in ecological studies of Fusarium diseases.
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  • Toshiaki TAKEHARA, Katsuto KUNIYASU
    1994 Volume 60 Issue 6 Pages 705-710
    Published: December 25, 1994
    Released: February 19, 2009
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    Methods of selective isolation of nitrate-nonutilizing mutants of Fusarium oxysporum from soil or infected plants on potassium chlorate-containing media and their applicability to ecological studies of F. oxysporum were examined. On a potassium chlorate-containing selective medium (MMCPA), nit mutants were selectively isolated from spore suspension, infested soil and infected plants. Naturally occurring strains of Fusarium could not grow on this medium. On a medium containing nitrate as a sole nitrogen source (MMPA), nit mutants showed very slight growth and could be distinguished from wild type strains of F. oxysporum. It was thought that by combination of the two selective media, MMCPA and MMPA, nit mutants and naturally occurring wild type strains of F. oxysporum can be detected separately. Thus, nit mutants may be used for ecological studies of F. oxysporum.
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  • Masahiro YOSHIDA, Takayuki NISHIYAMA, Takeo YAMAGUCHI, Kenzo KOBAYASHI
    1994 Volume 60 Issue 6 Pages 711-716
    Published: December 25, 1994
    Released: February 19, 2009
    JOURNALS FREE ACCESS
    Spore germination of the pathogenic Streptomyces sp. causing root tumor of melon was observed and effects of various treatments for activation of germiability of the spores were investigated. Both of the spores which formed on a culture medium for 14 days at 28°C (we called as “nascent spore”) and stored for 28 days at 5°C after sporulation with incubation for 28 days at 28°C (we called as “mature spore”) began to germinate with 3hr incubation at 28°C. Most of germinating nascent spores germinated within 24hr incubation, but germination of mature spores was retarded and the time to reach for its maximum germination rate was later than that of the nascent spores by 1 day or 2 days. Rates of germination on two kinds of media were 84.0-87.0% in nascent spores and 81.2-83.3% in mature spores, respectively, and about 10-20% of these spores were remained ungerminating spores. Among several heat shock treatments for activation of germiability of the spores, the most effective treatment was incubation at 40°C for 20min with which colony forming, ratio was 110.0-115.1% to non-treated control. Besides, in 6 spore activating agents tested with heat shock at 40°C for 20min, 0.00625-0.05% of sodium dodecyl sulfate (SDS) and 1.0-2.0% of yeast extract (YE) were effective for spore activation, particularly treatment with 0.025% of SDS was able to enhance the colony forming ratio to 121.2% of the control (only heat shock treatment). On the other hand, the combined use of 0.025% of SDS with 0.5-8.0% of YE resulted in lower colony forming ratio than treatment with 0.025% SDS alone. These results suggest that the spores of this pathogen include ungerminating ones which are considered to be in the dormant phase and its dormancy can easily be broken by the treatment with 0.025% SDS at 40°C for 20min heat shock.
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  • Norio NAKAZAWA, Norio NAKAZAWA, Chimao FUKUSHIMA, Yukio HARADA
    1994 Volume 60 Issue 6 Pages 717-724
    Published: December 25, 1994
    Released: February 19, 2009
    JOURNALS FREE ACCESS
    A new fruit rot disease widely occurred on stored apple fruits (Malus pumila Miller var. domestica Schneider) during the years of 1989-1990 and 1990-1991 in Aomori Prefecture. A Phytophthora sp. was isolated from the rotted fruits. In 1991, the same fungus was isolated from rotted fruits of Japanese pear (Pyrus serotina Rehder var. culta Rehder) and European pear (Pyrus communis L. var. sativa de Candolle) as well. Zoospore inoculation reproduced the symptoms on unwounded fruits of apple, Japanese pear, and European pear. The mycelial colony formed very characteristic ‘rose’ shaped growth zones on CV-8 A medium. The temperature for growth ranged from 0°C to 25°C with the optimum at 20°C. Sporangium was ovoid with a short pedicel, and non-deciduous, with a scarcely papillate apex. Hyphal swellings were present. Sexual organs developed in a single strain culture. Oogonium was spherical, thick wall, and almost completely filled with oospore. Antheridium was usually paragynous, and unicellular. Based on these morphological and cultural characters, we identified the causal fungus as Phytophthora syringae (Kleb.) Kleb. This paper is the first report on the occurrence of P. syringae in Japan.
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  • Yong-Jian FAN, Shigetou NAMBA, Shuichi YAMASHITA, Yoji DOI
    1994 Volume 60 Issue 6 Pages 725-728
    Published: December 25, 1994
    Released: February 19, 2009
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    Barley yellow dwarf virus (BYDV) distributed widely in barley, wheat, rye, oat, maize, teosinte and foxtail millet showing a yellowing, redding or dwarfing in Kanto area. Wheat, rye, maize, teosinte and foxtail millet were newly recorded natural host plants of BYDV in Japan. New diseases named yellow dwarf or yellows for them. Two BYDV isolates from maize and oat were characterized by the aphid transmission, host range, physicochemical properties, serology and intracellular appearance. These two isolates were regularly transmitted by Rhopalosiphum padi and R. maidis, respectively, indicating that the isolates may be differ from other known isolates of BYDV.
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  • Takanori MIYOSHI, Yasunobu TACHIBANA
    1994 Volume 60 Issue 6 Pages 729-734
    Published: December 25, 1994
    Released: February 19, 2009
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    A selective medium for isolation of Pseudomonas syringae (SPS), the causal agent of bacterial blossom blight of Kiwifruit was developed. The composition of the medium was as follows: NH4H2PO4 1.0g, KCl 0.2g, MgSO4⋅7H2O 0.2g, adonitol 2.0g, phenol red 20mg, methyl violet 1mg, pheneticillin potassium 50mg, cetrimide 10mg, agar 15g, pH 6.8 per 1.000ml of distilled water. Thirty two P. syringae strains pathogenic to Kiwifruit were grown on the medium and 31 strains showed convex colonies with entire margin. Color of the colonies was purple at the center and opalescent white at margin. One strain formed small opalescent white colonies. Colony forming efficiency of the medium was less than those of King's medium B. Twenty one isolates of Pseudomonas from Kiwifruit except P. syringae and 21 strains of phytopathogenic bacteria belonging to 5 genera were grown on the medium and they didn't grow with few exceptions which showed distinctive colonies from that of P. syringae. SPS was used for isolation of P. syringae from field-grown Kiwifruit. One hundred candidates were isolated and tentative characterization showed that all of them were identical with the P. syringae. Those results indicated that the possible application of the medium was useful for ecological studies of the bacterium in fields.
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  • 1994 Volume 60 Issue 6 Pages 735-741
    Published: December 25, 1994
    Released: February 19, 2009
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  • 1994 Volume 60 Issue 6 Pages 742-755
    Published: December 25, 1994
    Released: February 19, 2009
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  • 1994 Volume 60 Issue 6 Pages 756-764
    Published: December 25, 1994
    Released: February 19, 2009
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  • 1994 Volume 60 Issue 6 Pages 765-789
    Published: December 25, 1994
    Released: February 19, 2009
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  • 1994 Volume 60 Issue 6 Pages 790-796
    Published: December 25, 1994
    Released: February 19, 2009
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