Comparative efficacy of in vitro methods to culture rose powdery mildew (Podosphaera pannosa (Wallr.: Fr.) de Bary 1870)

Abstract

Powdery mildew of rose caused by Podosphaera pannosa (Wallr.: Fr.) de Bary 1870, is one of the most serious fungal diseases of roses grown in poly houses and field. Powdery mildew pathogen is biotrophic and no species of it can be grown in culture apart from its host for any significant duration and none can grow on dead plant material. Three different parameters viz. effect of temperature, effect of medium or support and inoculation method were evaluated in the present study for the maintenance of powdery mildew pathogen under laboratory conditions. The disease incidence was observed after 3 to 10 days post inoculation (dpi). The results showed that the temperature range 20°C to 23°C with spore dusting as inoculation method was the best method to maintain powdery mildew in vitro. Moist filter paper along with water agar, streptomycin (50 ppm) and 0.03% benzimidazole were found to be suitable matrix or support for rose leaves during incubation period. Using young twigs was found to be the most reliable method compared to detached rose leaves for disease development. The present study results provide a reliable method for in vitro maintenance of rose powdery mildew.