Japanese Journal of Phytopathology
Online ISSN : 1882-0484
Print ISSN : 0031-9473
ISSN-L : 0031-9473
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Volume 73, Issue 1
Displaying 1-11 of 11 articles from this issue
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Original
  • Scratch method for simple, rapid diagnosis of citrus huanglongbing using iodine to detect high accumulation of starch in the citrus leaves
    T. TAKUSHI, T. TOYOZATO, S. KAWANO, S. TABA, K. TABA, A. OOSHIRO, M. N ...
    2007 Volume 73 Issue 1 Pages 3-8
    Published: 2007
    Released on J-STAGE: September 14, 2007
    DOIhttps://doi.org/10.3186/jjphytopath.73.3
    JOURNAL FREE ACCESS
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    We demonstrated a rapid and simple diagnostic method (scratch method) for citrus huanglongbing (HLB) by detecting high accumulation of starch in the citrus leaves with the iodine-starch reaction. The average quantity of starch was 514.2 mg/kg in HLB-infected citrus leaves and 85.6 mg/kg in healthy leaves (Welch's t-test p<0.01), a significant difference in starch levels between diseased and healthy leaves. Based on this result, we devised a scratch method using abrasive paper for HLB diagnosis. Scratch the surface of a citrus leaf at least 20 times with abrasive paper, put the abrasive paper into 1 ml water in a vinyl pack, add to about 25 μl iodine solution 50 mM for dyeing starch. Iodine-reacted solutions show mostly ‘dark brown or black’ and ‘yellow or orange’ which are HLB-positive and negative, respectively. The scratch method and PCR assay of field samples showed more than 90% agreement. In addition, the scratch method did not give false HLB-positive reactions for healthy, nutrient-deficient or other disease leaves infected with Citrus tatter leaf virus and Hop stunt viroid. Therefore, the scratch method will be useful for rapid, simple detection of HLB in the field.
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  • Occurrence of concave stem canker of citrus in Ehime Prefecture and detection of the pathogenic fungus Lachnum abnorme by PCR
    T. MIYOSHI, Y. ONO, S. SHIMIZU
    2007 Volume 73 Issue 1 Pages 9-14
    Published: 2007
    Released on J-STAGE: September 14, 2007
    DOIhttps://doi.org/10.3186/jjphytopath.73.9
    JOURNAL FREE ACCESS
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    Brown lesions, a symptom of concave stem canker, were found on Citrus junos (Yuzu) in Hijikawa-cho, Ehime Prefecture, Japan in July 2000. The fungus isolated from the brown lesions by single-spore isolation was pathogenic on C. junos. By morphological characteristics of the specimen and culture and analysis of the ITS (internal transcribed spacer) region of the rDNA, the causal fungus was identified as Lachnum abnorme (Mont.) J. H. Haines & Dumont, and the disease was confirmed as concave stem canker of citrus. Based on small nucleotide differences in the ITS regions of seven isolates of L. abnorme, including pathogenic isolates on C. junos and eight other species of Lachnum, species-specific primers LAF (5'-CCTACCCTTGTGTATTATAACAAT-3') and LAR (5'-ATCCGAGGTCAACCTAAG-3') were selected. Primer pairs LAF and LAR amplified a fragment of 449 bp containing a portion of the ITS region in all the L. abnorme isolates tested, which originated from different hosts and regions of Japan, but did not amplify a fragment of any other species of Lachnum. In a PCR assay for concave stem canker, DNA was extracted from diseased branches of C. junos from Tokushima, Kochi and Ehime Prefectures using magnetic silica beads. Only a 449-bp fragment was amplified from DNA extracted from the brown lesions. The method developed may be useful for the rapid detection and identification of L. abnorme from both culture and plant tissue.
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  • The properties of elicitor-responsive photon emissions enhanced by pretreatment with plant defense activators
    C. KAGEYAMA, K. KATO, H. INAGAKI, H. IYOZUMI, K. FURUSE, K. BABA
    2007 Volume 73 Issue 1 Pages 15-20
    Published: 2007
    Released on J-STAGE: September 14, 2007
    DOIhttps://doi.org/10.3186/jjphytopath.73.15
    JOURNAL FREE ACCESS
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    Elicitor-responsive photon emissions from rice cells induced with one biotic (N-acetylchitohexaose) and two abiotic (dipotassium hydrogen phosphate, copper chloride) elicitors were characterized. Photon emission caused by each elicitor had its own characteristic pattern, although the changes in both the intensity and the time course differed among the elicitors. The lower the concentration of elicitor, the higher the increase in photon emissions, when acibenzolar-S-methyl, a plant activator, was the pretreatment. Although the degree of enhancement of elicitor-responsive photon emissions induced by each plant activator differed, a priming effect was observed for every combination of elicitor and plant activator except for copper chloride. Therefore, this phenomenon is thought to be common to a certain extent for elicitors. A novel screening method should make use of this phenomenon.
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