First report of powdery mildew on Dahlia (Dahlia variabilis) caused by Golovinomyces cichoracearum in Lahore, Pakistan

摘要

Dahlia (Dahlia variabilis Desf.) plants infected by powdery mildew were collected from different areas of Lahore Pakistan, in April 2011. Infected plants leaves surfaces were covered with white mycelium. The powdery mildew patches were slightly whitish gray with cylindric to doliform, hyaline conidia borne in chains. The conidia were 30–50 μm long × 14–20 μm wide. Conidiophores were unbranched, 110–220 long × 6–13 μm wide, composed of a foot cell and three to eight barrel-shaped conidia. Foot cells were 55–90 μm long and 6–13 μm wide, slightly swollen with constriction at the base. The cleistothecia were not observed. Fibrosin bodies were absent in conidiophores and conidia. Morphological characteristics and pathogenicity test confirmed the identification as Golovinomyces cichoracearum (DC.) V.P. Heluta. This is thought to be the first report of G. cichoracearum on D. variabilis in Pakistan.