Japanese Journal of Phytopathology
Online ISSN : 1882-0484
Print ISSN : 0031-9473
ISSN-L : 0031-9473
Volume 55 , Issue 5
Showing 1-20 articles out of 20 articles from the selected issue
  • Tomizo OHGUCHI, Katsuyuki YOSHIDA, Mohd. Yunus ISMAIL, Yasuji ASADA
    1989 Volume 55 Issue 5 Pages 561-566
    Published: December 25, 1989
    Released: February 19, 2009
    JOURNALS FREE ACCESS
    A method for propagation of Japanese radish-downy mildew fungus (Peronospora parasitica Pers.: Fr.) was developed using the seedlings of Japanese radish (Raphanus sativus Linn. var. horteinsis). Since the cotyledon and the true leaf of the seedling are resistant to the fungus, they were subjected to hot water (50C) treatment or the root was cut off to weaken resistance. Each of the cotyledons of cv. Awa-ichigo, Sarakamuri and Daimaru-shogoin, which had been grown for 7 to 11 days in the field and treated with hot water were put in a test tube (2.8×19cm) containing 15ml of distilled water after wrapping root with cotton. The upper surfaces of these cotyledons were inoculated by dropping a conidial suspension of the fungus. The percentage of the conidiophore formation on the cotyledons grown for one week at 20C, 1, 000lux after inoculation was highest on the 11-day-old cotyledon, treated with hot water for 60sec, of cv. Daimaru-shogoin. On the true leaf of 3-week-old seedlings, the percentage was highest on cv. Sarakamuri treated with hot water for 30sec. Since the cotyledons of cv. Shirokubi-miyashige, Heian-tokinashi and Daimaru-shogoin, which had been grown for 4 to 6 days in a growth chamber (25C, 5, 000lux), were very susceptible to hot water treatment, their roots were cut off instead. Cut surfaces of hypocotyls were wrapped with cotton wetted with sterilized distilled water or a modified Knop solution in order to keep the cotyledons from withering. The lower surfaces of cotyledons were inoculated with the suspension of conidium. The percentage of the conidiophore formation was highest on the 6-day-old cotyledon of cv. Shirokubi-miyashige. In the case of cv. Daimaru-shogoin, the 4-day-old cotyledon was best suited. A dark treatment (18hr) of the infected cotyledon on the 6th day after inoculation stimulated conidiophore formation following synchronized formation of the conidia. Also, many conidiophores were formed on the infected cotyledon when moved into an incubator (20C) afte: being stored in a refrigerator (5C) for two weeks from the 3rd day after inoculation.
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  • Hiroki TABIRA, Hiroshi OTANI, Norihiro SHIMOMURA, Motoichiro KODAMA, K ...
    1989 Volume 55 Issue 5 Pages 567-578
    Published: December 25, 1989
    Released: February 19, 2009
    JOURNALS FREE ACCESS
    Effect of light on sensitivity of apple and Japanese pear leaves to AM-toxin from Alternaria alternata apple pathotype was investigated. Continuous irradiation of light to leaves immediately after toxin exposure inhibited toxin-induced necrosis on susceptible apple and moderately resistant apple and pear leaves. When light irradiation was interrupted by inserting with darkness for specified times immediately after toxin exposure, a period of darkness longer than 5hr was required for necrosis development. However, the required period became shortened to about 3hr if lightcut-off started later than 2hr after toxin exposure. The action spectrum for the photoprotection was estimated to be 570-680nm; the most effective wavelength was near 602nm. The effective light was very specific to the necrosis induced by AM-toxin, and was not affected by treatment with photosynthetic inhibitors. Moreover, light did not affect toxin-induced electrolyte loss and reduction of photosynthetic CO2 fixation, early events in toxin action. When the leaves were inoculated with virulent spores or avirulent spores plus AM-toxin, light had no protective effect on fungal invasion, but inhibited the lesion development.
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  • Kazuo NAKASHIMA, Yoshio EHARA
    1989 Volume 55 Issue 5 Pages 579-585
    Published: December 25, 1989
    Released: February 19, 2009
    JOURNALS FREE ACCESS
    Two satellite RNAs were found in cucumber mosaic virus strain Y (CMV-Y) propagated in Nicotiana tabacum cv. Ky 57 in our laboratory; a larger molecular weight satellite RNA (Sat I) and a smaller one (Sat II). In virus from Ky 57 tobacco leaves which had been inoculated with genomic RNAs (RNAs 1-3) of the CMV, the satellite RNAs were not detected. This virus we termed CMV (-Sat). Symptoms on Ky 57 tobacco infected with CMV (-Sat) or with CMV (-Sat)+the satellite RNA(s) (Sat I or/and Sat II) were similar. However, addition of the satellite RNAs reduced yield of the virus by about half. The virus purified from tobacco (N. tabacum cvs. Ky 57 and Xanthi nc) leaves inoculated with CMV (-Sat)+Sat I contained only Sat I even after successive passages of the virus in tobaccos. The virus purified from tobaccos inoculated with CMV (-Sat)+Sat II contained both Sat I and Sat II, and Sat I became predominant after repeated passages of the virus in tobaccos. When tomato (Lycopersicon esculentum cv. Fukuju-nigo) was inoculated with CMV (-Sat), ordinary mosaic symptoms appeared with no necrotic symptoms. When the tomato was inoculated with CMV (-Sat)+the satellite RNAs, lethal necrosis appeared. The lethal necrosis was more severe when CMV (-Sat) was mixed with Sat I than when mixed with Sat II, and in these cases virus purified from the tomato expressing lethal necrosis symptoms contained only Sat I. Thus, it was suggested that Sat I was primarily involved in the tomato necrosis syndrome.
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  • Nobuhiro SUZUKI, Yukio SHIRAKO, Yoshio EHARA
    1989 Volume 55 Issue 5 Pages 586-593
    Published: December 25, 1989
    Released: February 19, 2009
    JOURNALS FREE ACCESS
    We examined the effects of concentration methods, extraction buffers, clarification reagents, and resuspension buffers on virus yield and purity by using SDS-polyacrylamide gel electrophoresis (SDS-PAGE), so as to establish optimal purification procedures of zucchini yellow mosaic virus (ZYMV), watermelon mosaic virus 2 (WMV2), and the watermelon mosaic virus 1 strain of papaya ringspot virus (PRSV-W). We then investigated the physicochemical properties of the three viruses. SDS-PAGE proved very useful to monitor virus purification in a small scale. The three viruses were purified with similar yields of 5-10mg per 100g of infected pumpkin leaves by the respective optimal methods. The procedures basically involved clarification with Triton X-100, differential centrifugation using a 20% sucrose pad, and 20-50% sucrose density gradient centrifugation. From WMV2 and PRSV-W purified preparations, capsid protein (CP) of 34, 000 (34K) was predominantly detected in addition to minor degradation products of 27K to 33K, respectively. A breakdown product of 28K was, however, as detectable as intact CP of 33K from ZYMV purified preparation. The RNAs of WMV2 and PRSV-W, which were a little larger than ZYMV RNA, were indistinguishable in size as evaluated with 1.7% agarose gel electrophoresis in denaturing conditions.
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  • Hiroyuki MUKOBATA, Takashi YAMAMOTO, Kiyonobu NAHATA, Takahito SUZUI
    1989 Volume 55 Issue 5 Pages 594-602
    Published: December 25, 1989
    Released: February 19, 2009
    JOURNALS FREE ACCESS
    The disease symptom first appeared on leaves as yellowish discoloration and was characterized by following production of grayish white lesions in various sizes on leaves of tulip plants. The symptoms are similar to those of tulip blossom blight caused by Phytophthora cactorum although the stems are not softly rotted. Cultivars ‘Red Matador’, ‘Ben van Zanten’, ‘Parade’, and ‘Queen of Night’ were susceptible and these varietical spectrum differed from those to tulip blossom blight. The pathogens were identified as Pythium dissotocum, P. afertile, P. sylvaticum and other unidentified one belonged to Pythium ‘group P’. Although retardation of growth of bulbs appeared, bulbs and roots were not infected. The weeds such as Polygonum conspicuum, Digitaria adscendens and Cyperus serotinus may be a major carrier of the disease.
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  • Hachiro OKU, Tomonori SHIRAISHI, Kei CHIKAMATSU
    1989 Volume 55 Issue 5 Pages 603-608
    Published: December 25, 1989
    Released: February 19, 2009
    JOURNALS FREE ACCESS
    Resistance mechanisms of pine against pine wilt disease were studied using the pine wood nematode and 2-year-old pine seedlings of which resistance to this disease being different. The pathogenic nematode multiplied most vigorously in the most susceptible pine, Pinus thunbergii, followed by P. densiflora. The increment was low in the moderately resistant pine, P. taeda, and no increment was found in highly resistant pine, P. rigida. The inoculated nematodes passed through cut stems of 2.5-cm length of both susceptible (P. thunbergii) and resistant (interspecific hybrid between P. taeda and P. rigida) seedlings. When stems were cut into 5-cm length, the inoculated nematodes passed through that of P. thunbergii, but not through stems of resistant interspecific hybrid. The heat treatment at 55C for 5min destroyed the resistance of the resistant stems. Thus, the resistance of interspecific hybrid seemed to be induced during nematodes migrated through at the point between 2.5 and 5.0cm from the inoculated site. The inoculated stems contained higher amount of nematode paralyzing substance than uninoculated ones.
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  • Nobuo HAYASHI
    1989 Volume 55 Issue 5 Pages 609-614
    Published: December 25, 1989
    Released: February 19, 2009
    JOURNALS FREE ACCESS
    The investigation was conducted to make clear the infection sources of the bacterial leaf blight of konnyaku (Amorphophallus konjac) caused by Pseudonomas pseudoalcaligenes subsp. konjaci. Survival of the pathogenic bacterium in the diseased leaflets, on corms and in soil was determined by using a selective medium. The bacterium could be isolated from the diseased leaflets kept for 422 days on the soil surface of natural field, but not be isolated 106 days after the leaflets were buried at a depth of 5cm in field soil. As the result of application of debris of the diseased leaflets onto soil surface of field immediately after planting corms, the disease occurred obviously on new leaflets grown from corms planted. When artificially infested corms were preserved at 10C of room temperature or in natural field soil, the bacterium could be recovered until 150 days after, namely until Apr. 14 in next spring. Survival of the bacterium in soil was longer at 5C than at 25C, but the bacterium could not be detected after 60 days at 5C in natural field. These results indicate that the residues of diseased leaflets and corms infested with this bacterium may be served as main infection sources of the next konnyaku cultivation.
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  • Ahmed A. MOSA, Masayasu KATO, Norio SATO, Kiroku KOBAYASHI, Akira OGOS ...
    1989 Volume 55 Issue 5 Pages 615-620
    Published: December 25, 1989
    Released: February 19, 2009
    JOURNALS FREE ACCESS
    The A2 mating type of Phytophthora infestans has been found in Japan. Oospores, within oogonia bearing amphigynous antheridia, were formed in a great abundance when compatible isolates were mated. When 207 isolates were tested for their mating types, 65 were A1, 141 were A2 and one was self-fertile in single culture. Both A1 and A2 isolates were detected among samples from many locations in Japan, but the A2 type was found to be predominant in all districts except Tohoku district. All A1 isolates except two were isolated from potato cultivars lacking R genes, while A2 isolates were isolated from a large number of cultivars having or lacking R genes. Most of the A2 isolates formed oospores in single aged cultures. There is a possibility that oospores have been formed in the fields of Japan.
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  • Kenji TAKAHASHI, Takeo YAMAGUCHI
    1989 Volume 55 Issue 5 Pages 621-628
    Published: December 25, 1989
    Released: February 19, 2009
    JOURNALS FREE ACCESS
    A fluorescence microscopic method was applied to assess directly the pathogenicity of resting spores of Plasmodiophora brassicae in soil. Infested soils were stained with a mixture solution of two fluorochromes, calcofluor white M2R and ethidium bromide, and were observed by fluorescence microscopy (phase contrast, UV filter set, oil immersion). Spores could be readily identified in soil by the strong blue fluorescence of the wall layer and classified into two groups, i.e. spores with a non-fluorescing cytoplasm (blue spores) and spores with a red fluorescing cytoplasm (red spores). When the infested soils were heated for 10 days at 40, 45 or 50C, both the percentage of blue spores in the soils and the disease severity in plants grown in the soils decreased with the time of incubation at all the temperatures tested, and the decrease was more rapid and appreciable at higher temperatures. Reduction in both the percentage of blue spores and the disease severity by heat treatment of the infested soil with a moisture ratio of 40% was more pronounced than that in the soil with a moisture ratio of 2.5% upon heating for 10 days at 45C. A positive correlation between the percentage of blue spores and the disease severity was also observed in the infested soils prepared by using the spores which were obtained from galls stored for different periods of time. Throughout these experiments, the percentage of blue spores showed a highly significant positive correlation with the pathogenicity of the spores in soil reflected by the disease severity. The results obtained indicate that the pathogenicity of the spores in a given soil sample can be directly assessed by the determination of the percentage of blue spores in the soil sample. The variations in the percentage of blue spores were generally less than those in the disease severity. This method is not only simple and rapid but also precise, and may enable to quantify the spore activity.
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  • Yoshikatsu FUJITA, Ryoichi SONODA, Hiroshi YAEGASHI
    1989 Volume 55 Issue 5 Pages 629-634
    Published: December 25, 1989
    Released: February 19, 2009
    JOURNALS FREE ACCESS
    To establish the effective method for inoculating the false smut fungus, Ustilaginoidea vixens, to rice plant, the injecting or the spraying inoculation method was attempted by using suspension of conidiospores produced on potato sucrose agar medium. About 2ml of conidial suspension was injected into the leaf sheath of rice plant at the booting stage. The inoculated plants were placed in an air conditioning room (Koitotron S type) for 2 days at 15C, and then incubated in a moist chamber for 5 days at 26C. After incubation, these plants were kept in a green house (25-35C) until smut balls appeared. The results obtained here seemed to indicate that the false smut disease was favored by low temperature (15C) and high humidity (100%) for infection, and by a relatively high temperature (25-35C) for appearance of the disease symptom. The successful results of inoculation were also obtained by means of spraying with a conidiospore suspension onto the rice plants in field. The proper time for inoculation seemed to be 10-30 days before heading of rice. This is the first report on the infection of the false smut by inoculation with conidiospores.
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  • Yoichi TAKANAMI, Naoto NITTA, Susumu KUBO
    1989 Volume 55 Issue 5 Pages 635-642
    Published: December 25, 1989
    Released: February 19, 2009
    JOURNALS FREE ACCESS
    Activity of membrane-bound RNA-dependent RNA polymerase (M-RDRP) from cucumber mosaic virus (CMV)-infected tobacco plants increased prior to virus multiplication and that of soluble enzyme (S-RDRP) increased rapidly after concentration of CMV has reached its maximum. In vitro products of M-RDRP was mainly doublestranded CMV RNAs as replicative forms. M-RDRP was suggested to be associated with endoplasmic reticulum (ER) by subcellular fractionation of the membrane-fraction using Percoll discontinuous gradient-centrifugation and electron microscopic observation. The ER-associated enzyme had viral RNAs as endogenous templates and was firmly integrated into membrane structure, even after treated with detergent or Mg++-depletion or partially purified by Sepharose 4B chromatography. The purification procedures could effectively remove S-RDRP which synthesized small heterogeneous RNA in vitro. Joined with our previous study using CMV-infected tobacco protoplasts, it was suggested that S-RDRP is a host-encoded enzyme induced in leaf tissues but not in protoplasts as a consequence of virus infection process like “Pathogenesis-related proteins.” We speculate that the CMV RNA replication complex is composed at least of translation products of viral RNAs, ER membranes and viral template RNAs.
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  • Yoshihisa HOMMA, Takahito SUZUI
    1989 Volume 55 Issue 5 Pages 643-652
    Published: December 25, 1989
    Released: February 19, 2009
    JOURNALS FREE ACCESS
    Strains RB425 and RB3292 of Pseudomonas cepacia, isolated originally from roots of lettuce and Campanula sp. and known producers of the antibiotics pyrrolnitrin and two pseudane compounds, both were suppressive to damping-off of radish caused by Rhizoctonia solani AG4 when applied on radish seeds. Two other naturally occurring strains A2 and A4 of P. cepacia, causal agents of bacterial brown spot of Cymbidium spp., and known producers of pyrrolnitrin (but not the two pseudanes), also were suppressive to damping-off of radish. A fifth strain, P. cepacia ATCC No.25416, produced no detectable quantity of any of the three antibiotics and was not suppressive to damping-off of radish. Eight mutants of strain RB425, induced by nitrosoguanidine (NTG), were distinguished from the wild-type parent by colony morphology. Three of these mutants produced no detectable quantities of either pyrrolnitrin or the two pseudanes in liquid culture and provided no suppression of damping-off. The other five mutants produced the three antibiotics in amounts similar to the parent and were suppressive to damping-off. Tests with derivative strains resistant to rifampicin and nalidixic acid showed that the mutants were not significantly different from the parent in the ability to colonize the roots of radish seedlings. Both colonization of radish seedlings by R. solani and severity of damping-off of radish caused by this fungus were suppressed by about 50% when the radish seeds were coated with either living cells of RB425 (107cfu/seed) or purified pyrrolnitrin (1.0μg/seed). Damping-off was suppressed only slightly or not at all following seed treatment with either of the two pseudane compounds, even at 40μg/seed. Observations by SEM confirmed that the effective strains multiplied in the spermosphere and the rhizosphere of radish seedlings. These results indicate that pyrrolnitrin plays an important role in suppression of radish damping-off by seed bacterization with P. cepacia.
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  • Mamoru SATO, Yoko SATO, Akira KATO, Koushi NISHIYAMA, Fukumi SAKAI
    1989 Volume 55 Issue 5 Pages 653-656
    Published: December 25, 1989
    Released: February 19, 2009
    JOURNALS FREE ACCESS
  • Hisatoshi KAKU, Toshihiko KIMURA
    1989 Volume 55 Issue 5 Pages 657-659
    Published: December 25, 1989
    Released: February 19, 2009
    JOURNALS FREE ACCESS
  • Masatoshi FUJIWARA, Tomonori SHIRAISHI, Hachiro OKU, Tetsuji YAMADA, S ...
    1989 Volume 55 Issue 5 Pages 660-663
    Published: December 25, 1989
    Released: February 19, 2009
    JOURNALS FREE ACCESS
  • Takefumi IKEDA, Yasuharu MAMIYA, Tsugio SHOJI
    1989 Volume 55 Issue 5 Pages 664-666
    Published: December 25, 1989
    Released: February 19, 2009
    JOURNALS FREE ACCESS
  • Tsunekuni MIYAKAWA, Kazunobu TSUNO
    1989 Volume 55 Issue 5 Pages 667-670
    Published: December 25, 1989
    Released: February 19, 2009
    JOURNALS FREE ACCESS
  • Masanobu FUKAMI, Keiko T. NATSUAKI, Fusao MOTOYOSHI, Keiichi TOMARU
    1989 Volume 55 Issue 5 Pages 671-675
    Published: December 25, 1989
    Released: February 19, 2009
    JOURNALS FREE ACCESS
  • Hiroshi KAMIUNTEN, Yasuhiro SUGA
    1989 Volume 55 Issue 5 Pages 676-679
    Published: December 25, 1989
    Released: February 19, 2009
    JOURNALS FREE ACCESS
  • Akio NAKAGAWA, Takeo YAMAGUCHI
    1989 Volume 55 Issue 5 Pages 680-683
    Published: December 25, 1989
    Released: February 19, 2009
    JOURNALS FREE ACCESS
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