First Record of Oidiopsis taurica Causing Powdery Mildew of Capparis spinosa in Egypt

Powdery mildew infections were observed on Capparis spinosa plants in Wadi El-Arbaein, Saint Katherine Protectorate, Egypt (28°32'43.1″N, 33°57'81″E, altitude 1,663 m) in the early fall to the end of winter of 2007 and 2008 when temperatures vary from the lowest mean value of 2.8°C to the highest mean value of 26.5°C. Symptoms first appeared as white, circular patches on the adaxial leaf surface (<1.3 cm in diameter), and as the disease progressed, both leaf surfaces were infected and these chlorotic areas eventually turned to necrotic lesions. Light microscopy revealed that the disease was caused by the anamorph stage of a powdery mildew fungus. Mycelium is predominantly endophytic with the presence of conidiophores emerging through leaf stomata. Conidiophores were simple or branched one or two times at random positions, 55 to 140 × 4.5 to 6 μm, producing conidia singly, and followed by two to three straight cells. Primary conidia were pyriform (68.9 × 18.5 μm) with a tapering end while secondary conidia were more cylindrical (59.1 × 18.0 μm). Mature conidia were hyaline, without distinct fibrosin bodies, and with angular/reticulated wrinkling of the outer walls. On the basis of these characteristics, the causal agent was identified as Oidiopsis taurica (1,3). The teleomorphic stage of the fungus was not observed. Pathogenicity tests were performed by inoculating three, potted, healthy C. spinosa plants with a fresh conidial suspension collected from powdery mildew colonies found on the infected plants (1 × 10⁴ conidia/ml) under the same field conditions. After 15 to 17 days, symptoms and signs of powdery mildew developed on the foliage of inoculated plants. Herbarium specimens of C. spinosa leaves infected with O. taurica were deposited at the Herbarium of Botany Department (SCU), Faculty of Science, Suez Canal University, Egypt. To our knowledge, this is the first record of a powdery mildew disease on C. spinosa in Egypt. Recently, Leveillula taurica, the teleomorph stage of O. taurica, was reported from C. spinosa in Turkey (2). References: (1) U. Braun. Beih. Nova Hedwigia 89:1, 1987. (2) H. Kavak. Plant Pathol. 53:809, 2004. (3) J. Palti. Bot. Rev. 54:423, 1988.