Molecular Plant Pathology – Pathogen Profiles

The tomato powdery mildew fungus Oidium neolycopersici

Hannah Jones1, John M. Whipps2, and Sarah Jane Gurr1

Department of Plant Sciences, South Parks Road, University of Oxford, Oxford, OX1 3RB, UK,
Horticulture Research International, Wellesbourne, Warwick, CV35 9EF, UK

Summary:Powdery mildew fungus; Ascomycete although sexual stage is yet to be found; an obligate biotroph.
Identification:Superficial mycelium with hyaline hyphae; unbranched erect conidiophores; conidia, ellipsoid-ovoid or doliform, 22-46 x 10-20 痠, lack fibrosin bodies; conidia formed singly, rarely in short chains of 2-6 conidia; appressoria lobed to multilobed, rarely nipple-shaped. Pseudoidium species.
Host range:Broad, reported to attack over 60 species in 13 plant families, particularly members of the Solanaceae and Curcubitaceae.
Disease symptoms:Powdery white lesions on all aerial plant parts except the fruit. In severe outbreaks the lesions coalesce and disease is debilitating.
Agronomic importance:Extremely common in glasshouse tomatoes world wide but increasing in importance on field grown tomato crops.
Control:Chemical control and breeding programmes for disease resistance.