APS Homepage

Poster: Biology & Disease Mgmt: Genetics of Resistance


Development of an in vitro bioassay to screen perennial Phlox germplasm for susceptibility to Golovinomyces cichoracearum (Erysiphe cichoracearum)
C. FARINAS (1), P. Jourdan (1), F. Peduto Hand (1) (1) The Ohio State University, U.S.A.

Phlox is a genus of perennial and annual plants with colorful, long-lasting flowers, and a common inhabitant of gardens worldwide. In humid and warm areas, its cultivation is severely limited by powdery mildew. Published studies on resistance of Phlox to powdery mildew have mainly focused on the species subulata, paniculata and drummondii. However, the genus includes many more species, some of which could be valuable from both an ornamental and resistance standpoint. This project aims to develop a reliable laboratory bioassay to conduct in vitro screenings of Phlox germplasm for susceptibility to powdery mildew. The project is in collaboration with the OSU Ornamental Plant Germplasm Center, which allows access to more than 65 species of Phlox. For this purpose, detached leaves of healthy Phlox were disinfected and plated on water-agar medium. Variations of the host species, media type, disinfection process, and inoculation technique were evaluated. Disinfected leaf tissues remained in good status and contaminant-free for up to one month. Infection and growth of the pathogen on the host required specific conditions of light, temperature and relative humidity. To the best of our knowledge, this study represents the first attempt to develop a laboratory bioassay to screen Phlox resistance to powdery mildew. This assay has the potential to represent a useful tool for screening resistant lines and for phytopathological studies on the biology of the pathogen.