• Title/Summary/Keyword: leaf spots

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A Target Leaf Spot Disease Caused by Corynespora cassiicola on Cucumber Cultivated in Green House (시설하우스에서 Corynespora cassiicola에 의해 발생하는 오이 갈색무늬병)

  • Kwon, Mi-Kyung;Yang, Kwang-Yeol;Cho, Baik-Ho
    • Research in Plant Disease
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    • v.10 no.2
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    • pp.121-125
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    • 2004
  • An epidemic of target leaf spot of cucumber (Cucumis sativus) occurred in commercial greenhouses in Korea in 2000/2001. The early symptoms on the leaves were small brown spots with yellow halos. These lesions became irregular enlarging in diameter and eventually defoliation resulted. The causal agent was a fungus with morphological characteristics matching Corynespora cassiicola. The sequence of the ITS region of C. cassiicola CM2000-1 was identical to that of an authentic strain of Corynespora cassiicola. Optimal germination of spores and mycelial growth on plate was at 3$0^{\circ}C$. A long dew period on the leaf surface and high temperatures were the main contributing factors for disease development and the greenhouse epidemic. Artificial inoculation of the Korean isolate of C. cassiicola revealed resistance in some Korean cucumber cultivars.

Incidence Rates of Major Diseases on Green-Fleshed Kiwifruit cv. Hayward and Yellow-Fleshed Kiwifruit cv. Haegeum (그린키위 품종 헤이워드와 골드키위 품종 해금의 주요 병 발병률)

  • Kim, Gyoung Hee;Koh, Young Jin
    • Research in Plant Disease
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    • v.24 no.3
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    • pp.175-181
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    • 2018
  • Incidence rates of bacterial canker, bacterial leaf spot and postharvest fruit rot on the Korean yellow-fleshed kiwifruit cv. Haegeum were compared with those on the most popular green-fleshed kiwifruit cv. Hayward grown in several naturally infected kiwifruit orchards in 2013 and 2014. The percentages of diseased leaves caused by bacterial canker were 18.5% and 17.3% on Hayward in 2013 and 2014, but those on Haegeum were 1.2% and 0%, respectively. The percentages of diseased leaves caused by bacterial leaf spot on Hayward were 63.5% and 16.2% in 2013 and 2014, respectively, but no bacterial leaf spots were observed on Haegeum in both years. The average percentages of diseased fruits caused by postharvest fruit rot were 24.2% and 20.5% on Hayward in 2013 and 2014, while 6.3% and 4.4% and Haegeum, respectively. Botryosphaeria dothidea was turned out to be the major pathogen of postharvest fruit rot on both cultivars.

Studies on the Effects of Ozone Gas in Paddy Rice;II. Effect of Ozone Gas on Varieties of Rice (수도생육(水稻生育)에 대(對)한 Ozone가스의 영향(影響)에 관(關)한 연구(硏究);제2보(第2報) Ozone가스에 대(對)한 수도품종별(水稻品種別) 영향(影響))

  • Kim, Bok-Young;Kim, Sun-Kwan;Kim, Bok-Jin
    • Korean Journal of Environmental Agriculture
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    • v.1 no.2
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    • pp.129-133
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    • 1982
  • This study was conducted to find out the resistance of rice varieties to ozone gas. Thirty eight rice varieties were exposed to 0.3 ppm $O_3$ gas for 3 hours. Damage symptom, percentage of destroyed leaf and chlorophyll contents were observed after $O_3$ fumigation. The results obtained are as follows. 1) Typical symptom of $O_3$ damage appeared to greyish subtle spots in Japonica type and redish brown subtle spots in Indica-Japonica hybrid type within rice leaf vein. 2) Resistant varieties to $O_3$ gas were Palgwangbyeo, Seokwangbyeo and Milyang 30, while sensitive ones were Gwanakbyeo, Jinjubyeo and Hankangchalbyeo. 3) Chlorophyll damage of rice leaves were higher in Nongbaeck, Dobongbyeo, Palgeum, Jinjubyeo than in Milyang 21, Podgwangbyeo, Josaeongtongil, Honamjosaeng, Hwanggeumbyeo. 4) The amount of chlorophyll damage showed highly significant positive correlation with that of leaf destruction.

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Seasonal Prevalence of Bacterial Canker of Kiwifruit in Boseong in 2014 and 2015 (2014년과 2015년 전남 보성에서의 키위 궤양병의 계절별 발생소장)

  • Son, Kyeong In;Kim, Gyoung Hee;Choi, Eu Ddeum;Kim, Kwang-Hyung;Lee, Young Sun;Jung, Jae Sung;Koh, Young Jin
    • Research in Plant Disease
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    • v.22 no.4
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    • pp.217-226
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    • 2016
  • Seasonal prevalence of bacterial canker of kiwifruit caused by Pseudomonas syringae pv. actinidiae (Psa) was investigated at a naturally infected orchard in Boseong, Jeonnam in 2014 and 2015. Stem canker began to occur in mid-February in 2014 and early March in 2015. Bacterial ooze was observed on canes, leaders and trunks until late May and gradually disappeared thereafter. The percentages of infected trees were 44.7% and 69.7% in 2014 and 2015, respectively. Trees with trunk canker in a previous year died in 2015. Leaf canker symptoms began to appear as brown spots with chlorotic halos in early May and irregular dark brown spots without halos were observed under humid conditions. Leaf canker progressed until mid-July in 2014 and late July in 2015. No Psa was detected from the leaf lesions on leaves thereafter, but new infection of Psa was observed on leaves in late October. Infected blossoms with blighted calyx were sometimes observed from mid-May. Optimal monitoring period to detect Psa was May when it could be easily detected from stems, leaves and blossoms. Disease cycle of bacterial canker of kiwifruit modified for Korea was proposed based on the seasonal prevalence of bacterial canker analyzed according to weather data in Boseong, Jeonnam over 2 years.

Bacterial Leaf Spot of English Ivy Caused by Xanthomonas hortorum pv. hederae (Xanthomonas hortorum pv. hederae에 의한 헤데라 세균성점무의병)

  • Lee, Seung-Don;Lee, Jung-Hee;Han, Kyoung-Suk;Seo, Sang-Tae;Kim, Yong-Ki;Heu, Sung-Gi;Ra, Dong-Soo
    • Research in Plant Disease
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    • v.13 no.1
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    • pp.61-65
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    • 2007
  • English ivy (Hedera helix) in Araliaceae family is an evergreen climbing vine. A severe bacterial disease of English ivy was observed and investigated in January 2005. Initial symptoms on the leaves appeared as small water-soaked lesions on the lower surface. As the spots enlarged, the center became brown to brownish black and greenish-brown water-soaked, irregular margins surrounded the center, The spots developed into large irregular blotches, sometimes 5$\sim$10 mm in diameter, then coalesced. Finally, the water-soaked margins raised, dried out, became corky and broke in the center. A bacterial organism, isolated from the advancing margins of the lesions, was tested for its pathogenicity according to the Koch's postulates and biochemical and physiological tests identified the isolated bacterium as a Xanthomonas. The representative Xanthomonas strains (SL4821 and SL4822) isolated from English ivy were compared with a reference strain X. hortorum pv. hederae for fatty acid profiles, metabolic fingerprints and 16s rDNA sequences, showing that all outcomes were indistinguishable between the representative and reference strains. This is the first report of bacterial leaf spot of English ivy in Korea.

Plant regeneration from suspension-cultured cell clusters of Arabidopsis thaliana (애기장대(Arabidopsis thaliana)의 현탁배양세포괴로부터 식물체 재분화)

  • 김명덕;김준철;진창덕;임창진;한태진
    • Korean Journal of Plant Tissue Culture
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    • v.25 no.3
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    • pp.195-200
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    • 1998
  • Callus induction from leaf and stem explants of Arabidopsis thaliana was successfully obtained when leaf explants were cultured on MS medium containing 2.0 mg/L 2,4-D in the dark and also, when stem explants were cultured on CP medium containing 0.5 mg/L 2,4-D and 0.1 mg/L BAP. Explant-derived sliced calli were suspension-subcultured every week in CP liquid medium with 0.5 mg/L 2,4-D and 0.1 mg/L BAP in the dark, and shoot-forming cell clusters of nodular, pale yellow and knobby type were selected after 7-8 weeks of culture. Shoots were initiated from the green spots of the selected shoot forming calli cultured on MS regeneration medium containing 0.05 mg/L IAA, 7.0 mg/L 2-iP and 30 g/L sucrose under continous illumination for four weeks. Shoot regeneration frequency (calli regenerating at least one shoot) was more than 50%. For plant regeneration, excised shoots were trnasferred to hormone free medium for root initiation after 4 weeks of culture. The regenerants were bolting after 2 weeks of culture and formed in vitro flowering buds within bracts after 4 weeks of culture.

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Development of a Model for Estimating Leaf Area and the Number of Flower Using Leaf Length and Width of Farfugium japonicum Kitam. (털머위(Farfugium japonicum Kitam.)의 엽장과 엽폭을 이용한 엽면적 및 개화 수 추정 모델 개발)

  • Dae Ho Jung;Yong Suk Chung;Hyunseung Hwang
    • Journal of Bio-Environment Control
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    • v.32 no.2
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    • pp.115-121
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    • 2023
  • The leopard plant has the characteristic of being used for ornamental purposes when there are yellow spots on the leaves, and is widely used as a bed plant for viewing flowers. To set several indicators to predict the growth of crops with ornamental value, and to quantitatively express the relationship between the indicators are necessary. In this study, we determine a model that estimates the leaf area and the number of flower of Farfugium japonicum Kitam. using leaf length and width, and conducting a regression analysis on some regression models. As an indicator for estimating the leaf area and the number of flower, the leaf length and width of F. japonicum were measured and applied to 8 regression models. As a result of regression analysis of 8 models that estimated leaf area and the number of flower, R2 values of the linear models were all higher than 0.84 and 0.80. As a result of validation, using the most reliable model among the models for estimating the leaf area and the number of flowering, R2 was 0.90 and 0.82, respectively. Using a model that estimates various indicators that can be used for quality evaluation from easy-to-measure morphological factors, the evaluation of ornamental plants will be facilitated.

Studies ell the strawberry leaf flight Caused by Dondrophoma obscurans (Ell. & Ev.) Anderson (우리나라의 딸기 신병해 겹무늬병 (Dondrophoma obscurans)에 관한 연구)

  • Cho Chong Taik;Moon Byeong Joo
    • Korean journal of applied entomology
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    • v.18 no.4 s.41
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    • pp.183-188
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    • 1979
  • The study has been carried to describe a new disease of strawberry in Korea, which was found in 1977 at Kimhae. Symptom of the disease occurred mainly on leaves as showing large annular brown spots or 'V' shaped brown lesions. Many of dark pycnidia were observed from the both side of old lesions. The pathogen was identified as Dendrophoma obscurans (Ell. & Ev) Anderson which has not been described in Korea as a pathogen of strawberry disease. The common name of the disease was given, temporaly, as Annular leaf blight of strawberry. In the laboratory study, light was necessary for the production of pycnidia and potato dextrose agar was the best media for tile pycnidia formation. There were some difference on resistance to the disease among 48 tested strawberry varieties though none of them shelved highly resistant reaction, and the older leaves showed more susceptible reaction than younger ones.

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A Simple Method for Sporangial Formation of the Rice Downy Mildew Pathogen, Sclerophthora macrospora

  • Lee, Hyeong-Jin;Han, Seong-Sook;Kweon, Jin-Hyeuk
    • The Plant Pathology Journal
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    • v.18 no.2
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    • pp.77-80
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    • 2002
  • A simple method for sporangial formation of the rice downy mildew pathogen, Sclerophthora macrospora, on infected leaf tissues was developed to facilitate diagnosis of the disease. Freshly infected young leaves showing whitish to yellowish small spots were selected and cut into small pieces about 2-3 cm in length. About 10-20 pieces were surface sterilized in a 100 ml Duran bottle with 40 ml of 70% ethanol by vigorous shaking for 30 seconds. After washing three times with distilled water, the leaf cuts were submerged in 10 ml of Millipore-filtered paddy water and incubated at $20^{\circ}C$ in the dark. After 8-10 h of incubation, the bottle was vigorously agitated on a vortex mixer, Aliquot amount of the suspension, 0.1-1.0 m1, was spread on a slide glass and examined under a light microscope at 50 or 100x magnification. It was found that light and 1% NaClO strongly inhibit sporangial formation of S. macrospora. Meanwhile, the use of freshly infected young loaves and washing with 70% ethanol stimulated sporangial formation of the fungus on rice leaves.

Occurrence of Eggplant Scab Caused by Cladosporium cucumerinum in Korea

  • Kwon, Jin-Hyeuk;Kang, Soo-Woong;Park, Chang-Seuk
    • The Plant Pathology Journal
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    • v.15 no.6
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    • pp.345-347
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    • 1999
  • A scab disease on eggplant (Solanum melongena L. cv. Chukyang) in plastic film houses around Kimhae area in Korea during the winter season of 0998-1999. The disease started on leaves with small dark brown spots which were gradually expanded to 1 to 3 mm diameter lesions. Later, the central parts of the lesions became collapsed and detached to make holes. Dark brown mold was grown out of the lesions on the lower side of leaf. Numerous conidia were produced on the lower side of leaf. Numerous conidia were produced on the diseased leaves and appeared to be readily dispersed in the air. A fungus was isolated from the diseased leaves, and tested for Koch's postulates to prove the causal agent of the desease. The isolated fungus grew on potato dextrose agar, forming greenish black to pale brown colonies. Conidia were ellipsoidal, fusiform or subspherical, mostly one-celled but occasionally septated, and formed in long branched chains on the erected conidiophores which were pale olevaceous brown and variable in length between 12.4 and $393.4\mu\textrm{g}$. The fungus was identified as Cladosporium cucumerinum Ellis Arthur based on the above morphological characteristics examined. The optimum temperature for mycelial growth and conidial formation was about 20 to $25^{\circ}$. In addition to cucumber, the fungus was also pathogenic to watermelon, pumpkin and oriental melon. This is the first report on the scab disease of eggplant in Korea.

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