شناسایی عوامل ایجاد کننده لکه برگی‌ و سفیدک در مزارع سبزی و صیفی و گیاهان زراعی استان خوزستان

Foliar diseases are an important group of plant diseases in humid and warm regions. These diseases are caused by a large number of deuteromycetes, powdery and downy mildews. Different vegetable and crop fields including cucumber (Cucumis sativus), okra (esculentus Abelmoschus), quinoa (Chenopodium quinoa), cabbage (Brassica oleracea var. capitata), sun flower (Helianthus annuus), tomato (Solanum lycopersicum), eggplant (Solanum melongena), potato (Solanum tuberosum) in Mollasani, Shooshtar, Safi Abad and Shush city were survived during 2017-18. In these visits, many leaf spots and mildew symptoms were observed and samples were collected from symptomatic plants. In order to identify the mildews, microscopic slides were directly prepared from infected leaves. Also, the leaf spots were cultured on potato dextrose agar (PDA) and corn meal agar (CMA) and microscopic slides were prepared after purification. Microscopic slides were investigated by light microscope and identified using corresponding literature. The results showed that Pseudoperonospora cubensis the causal agent of downy mildew in cucumber, Erysiphe cichoracearum the causal agent of powdery mildew in okra fields, Peronospora variabilis the causal agent of downy mildew in quinoa fields, Hyaloperonospora brassicae the causal agent of downy mildew in cabbage fields, Erysiphe cichoracearum and Alternaria sp. the causal agent of powdery mildew and target spot respectively in sunflower, Alternaria solani the causal agent of target spot in tomato fields(Alternaria sp.), Sclerotinia sclerotiorum the causal agent of white mold in eggplant fields, Phytophthora infestance and Alternaria solani the causal agent of late blight and target spot respectively in potato fields were the main causal agents of foliar diseases in survived fields. Due to warm and humid climate in Khuzestan province, leaf diseases can be observed frequently in different fields. Also, this is the first report of quinoa downy mildew in Khuzestan province.