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Journal of Plant Diseases and Protection






Springer Berlin Heidelberg


The fungal pathogen Didymella bryoniae causes gummy stem blight and black rot on a broad spectrum of cucurbits. However the substantial differences in susceptibility among Cucurbitaceae are not well studied. Susceptibility was characterized with muskmelon (Cucumis melo), watermelon (Citrullus lanatus), cucumber (Cucumis sativus), pumpkin (Cucurbita pepo), and zucchini (C. pepo). Lesion diameters on leaf disks inoculated with agar plugs were measured 7 days after inoculation, and the necrotized areas of leaf disks inoculated with conidial suspensions were measured 48 h after inoculation (hai). For each species, the number of trichomes was counted on 16 leaf pieces using a stereomicroscope. Lengths of ≥21 trichomes per species were measured. Polyphenol autofluorescence was recorded at 48 hai and quantified. Watermelon had the lowest trichome density and the shortest trichomes. Zucchini showed the highest trichome density, and pumpkin had the longest trichomes. Trichome density was negatively correlated with mean necrotized leaf area, and trichome length was highly negatively correlated with lesion diameter. Mean fluorescing area was correlated with lesion diameters and mean necrotized leaf area. This is the first study in which trichome morphology and polyphenol autofluorescence in inoculated cucurbit leaves were correlated with susceptibility to D. bryoniae.


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