Plant Pathology (2004) 53, 528 Doi: 10.1111/j.1365-3059.2004.01020.x 528 © 2004 BSPP Blackwell Publishing, Ltd. NEW DISEASE REPORT First report of powdery mildew caused by Podosphaera phaseoli (syn. Sphaerotheca phaseoli ) on cowpea (Vigna sinensis) in Turkey E. M. Soylu, S. Soylu* and S. Kurt Department of Plant Protection, University of Mustafa Kemal, Faculty of Agriculture, 31034 Hatay, Turkey During the summer of 2003, typical symptoms of powdery mildew were observed in many cowpea fields assessed in Hatay Province, Turkey. White, epiphytic mycelia and conidia, characteristic of a powdery mildew, were present on leaves, stems and inflorescences. The plant tissue under- neath the mycelial patches was purplish in colour. Mycelial growth was amphigenous, thick, forming irregular white patches, sometimes effused to cover the whole leaf surface, and had poorly developed nipple-shaped single appressorium. Simple straight conidiophores (115–190 × 10–13 μm) developed mostly singly from a hyphal cell, arising from the upper part of mother cells, having the basal septum at the branching point of the mycelium with a sharp constriction. Each conidiophore had three to eight barrel-shaped conidia formed in chain. Conidia with fibrosin bodies were 28–42 × 15–18 μm in size and ger- minated below the shoulder by producing a simple germ tube. Dark brown ascomata, found on leaves and stems as embedded in the mycelial felt, were spherical, gregarious to subscattered and measured 85–105 μm in diameter. Appendages (six to 15) were myceloid, arising from the lower half of the ascomata, brown, paler upward and 6– 8 μm wide. The ascomata contained single ascus (65– 95 × 55–67 μm). The ascus contained eight ellipsoidal to ovoid ascospores (18–24 × 12–16 μm). On the basis of morphological characters of the conidial stage and tele- omorph, the fungus was identified as Podosphaera phaseoli (syn. Sphaerotheca phaseoli) (Braun & Takamatsu, 2000; Shin, 2000). Pathogenicity tests were conducted on 4- week-old cowpea plants, cv. Libye, by shaking fresh conidia from naturally infected plants onto the healthy leaves. Inoculated plants were kept in a moist chamber (100% RH) for 2 days and then maintained a growth chamber at 22 ± 2°C, 75% RH with a 16 h photoperiod. After 7–10 days, inoculated plants developed powdery mildew symptoms, which were similar to those observed on naturally infected plants. This is the first report of powdery mildew on cowpea in Turkey. Previous reports list P. phaseoli on Vigna spp. in Korea (Shin & La, 1992; Lee et al., 2002) and the same species P. phaseoli was also reported on several related host plants such as Phaseolus spp. and Rhynchosia volubilis (Shin, 2000). Although bean is the one of the alternative hosts of the disease agent and grown in nearby cowpea plants in the same field, no disease symptoms were observed on bean plants. References Braun U, Takamatsu S, 2000. Phylogeny of Erysiphe, Microsphaera, Uncinula (Erysiphaceae) and Cystotheca, Podosphaera, Sphaerotheca (Cystotheceae) inferred from rDNA ITS sequences – some taxonomic consequences. Schlechtendalia 4, 1–33. Lee SY, Hwang SJ, Lee SB, 2002. Occurrence of powdery mildew on mung bean (Vigna radiata L.) caused by Sphaerotheca phaseoli. Research in Plant Disease 8, 166–70. Shin HD, 2000. Erysiphaceae of Korea. Suwon, Korea: National Institute of Agricultural Science and Technology. Shin HD, La YJ, 1992. Addition to the new records of host plants of powdery mildews in Korea. Korean Journal of Plant Pathology 8, 57– 60. *E-mail: soylu@mku.edu.tr Accepted 7 January 2004 at www.bspp.org.uk/ndr where figures relating to this paper can be viewed