مطالعه عامل بيماري بلايت باكتريايي كدوييان در ورامين و ارزيابي مقاومت تعدادي ازارقام و لاين هاي خيار نسبت به آن

ETIOLOGY OF BACTERIAL BLIGHT OF CUCURBITS IN VARAMIN AND REACTION OF SOME CUCUMBER CULTIVARS AND LINES TO THE PATHOGEN

Foliage blight symptoms have been observed on cucumber (Cucumis sativus), cantaloup (Cucumis melo) and squash (Cucurbita pepo) plants in Varamin since 1996. Symptoms consist of marginal mecrosis sorrounded by chlorotic halos that expand as V-shaped blotches along and between the major leaf veins. The blight has been severe during and following periods of wet and rainy weather when the day-time temperature averaged 27-30°C. A rod-shaped, Gram-negative, oxidase positive, fluorescent Pseudomonas was consistently isolated from the diseased leaves on medium B of King. On the basis of the phenotypic features, the strains were identified as Pseudomonas marginalis pv. marginalis. The electrophoretic profiles of cell proteins of the strains were similar to each other and to a reference strain of Pseudomonas marginalis pv. marginalis IC MP 3553. Pathogenecity of the strains was confirmed on cucumber (cv . Soltan and line RS- 410332 ) under greenhouse conditions, and strains were isolated from the inoculated plants. To evaluate the resistance of cucumber cultivars to the pathogen, an experiment using 77 cultivars and lines was performed under greenhouse conditions (22-30 °C). The majority of cucumber cultivars and lines were rated as susceptible and a few rated tolerant to P. in. pv. marginalis. cultivars and lines Kozakloo, G1-14, KC 361106, KC 361065, TN 94162, TN 94139, TN94190 and Super shoal appeared to be tolerant.