Didymella bryoniae is a pathogenic fungus that causes gummy stem blight GSB in Cucurbitaceae crops e. GSB produces lesions on the stems and leaves, and can also be spread by seeds. The sensitivity and specificity of the LAMP assay were further analyzed in comparison with those of a conventional polymerase chain reaction PCR. The LAMP assay could be accomplished in about 45 min, with the results visible to the naked eye. The assay showed high specificity in discriminating all D.
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In , greenhouse-produced transplants of watermelon Citrullus lanatus developed water-soaked lesions on leaf petioles and main stems. As disease progressed, petioles and stems became necrotic and shriveled, and exuded a sticky, translucent tan liquid.
Symptoms spread to leaves, which wilted and collapsed. Affected transplants eventually died. Although fruiting bodies were not observed on diseased plants, a fungal agent was consistently isolated from symptomatic tissues.
Under the same incubation conditions, isolates on V8 juice agar produced sparse ostiolate pseudothecia with bitunicate asci and hyaline, oval, one-septate ascospores with mean dimensions of Based on these characters, the isolates were identified as Didymella bryoniae anamorph Phoma cucurbitacearum 1,2.
Pathogenicity was tested by producing conidial inocula of representative isolates and inoculating wounded cotyledons, true leaves, and petioles of watermelon cv. Sangria , and wounded true leaves and petioles of cucumber Cucumis sativus cv.
Premier Hybrid 3. Sterile, distilled water was applied to corresponding wounded tissues of control plants. All plants were kept in a humid chamber for 4 days. After 6 watermelon to 10 cucumber days, inoculated plants exhibited water-soaked lesions followed by necrosis, petiole and leaf wilting, and shriveling of tissues. Pycnidia were observed on cucumber plants after 18 days. The pathogen was reisolated from all inoculated plants and identified as D. Control plants developed no disease symptoms.
In addition, agar plugs colonized with the watermelon isolates were placed onto cucumber fruit that were wounded slightly with a sterile scalpel. The same pathogen was reisolated from the margins of fruit lesions. Wounded control fruit received sterile agar plugs and did not develop any symptoms. This is the first documentation of gummy stem blight on watermelon transplants in California. References: 1 W. Chiu and J.
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Send even when there aren't any new results. Optional text in email:. Save Cancel. Create a file for external citation management software Create file Cancel. Full-text links Cite Favorites. Abstract In , greenhouse-produced transplants of watermelon Citrullus lanatus developed water-soaked lesions on leaf petioles and main stems. Boughalleb N, et al. Plant Dis. PMID: Jensen BD, et al. Tsai YC, et al. Ligoxigakis EK, et al.
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List of symptoms / signs
Didymella bryoniae causes the cucurbit-rot disease known as gummy stem blight or black rot. Both the sexual and asexual stages Phoma cucurbitacearum can cause disease and are present in most regions where watermelon is grown 3. Didymella bryoniae infects watermelon, cantaloupe, cucumber, squash, and other cucurbit hosts. All parts of the plant can display symptoms and signs but the roots. Early symptoms appear as yellowing or chlorosis of the leaf margins followed by light to dark brown necrotic spots. Pale brown or gray spots develop on the leaves, petioles, and stems. Lesions usually form at the joints on the stem, become elongated, cracked, and exude amber colored sap.
Ascochyta citrullina Chester C. Niessl, Didymosphaeria effusa Niessl Didymosphaeria melonis Pidopl. Diplodina citrullina Chester Grossenb. Walker, Mycosphaerella melonis Pass.
Didymella bryoniae occurs on Cucurbits exclusively. Hosts include watermelon, melon, pumpkin, cucumber, squash, bittermelon, smooth luffa, and angled luffa. Gummy stem blight shows a variety of symptoms which are referred to as leafspot, stem canker, vine wilt, and black rot or fruit. The appearance of spots on the leaves, petioles and stems are a typical sign of infection which usually become pale brown or gray. Spots on stems often elongate into streaks usually starting at the joints and have an amber exudate of gummy material.