First Report of Bacterial Leaf Spot Caused by Pseudomonas syringae pv. viburnii on Viburnum sargentii in Italy

Plant Disease
A GaribaldiM L Gullino

Abstract

During the spring of 2003, plants of Viburnum sargentii, a species mostly used in gardens as low-maintenance hedges, showing symptoms unlike those of known diseases were observed in some private gardens in the Biella area (northern Italy). Lesions on leaves were the only symptoms seen. Lesions started as water-soaked, circular areas that in 4 days developed into irregular, shrunken, brown spots from 2 to 4 mm in diameter. The core of older lesions appeared somewhat transparent. Leaves dried up completely 3 weeks after symptoms were first seen. No fungal structures were observed in lesions. Microscopic examination of affected leaf tissues revealed abundant bacterial ooze from the cut margin of lesions. Small fragments of tissue from affected leaves were macerated in nutrient yeast dextrose broth (NYDA) and dilutions of the resulting suspension were streaked onto NYDA and potato dextrose agar (PDA). Isolations were made from at least 25 leaves. Plates were maintained at 22 ± 1°C for 48 h. Slightly yellow colonies typical of Pseudomonas species were consistently isolated on NYDA. No fungi were isolated from the spots on NYDA or PDA. Levan production, oxidase production, pectinolytic activity, arginin dihydrase production, and toba...Continue Reading

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