Evaluation of Resistance of Rose Cultivars and Wild Rose to Powdery Mildew and Black Spot

Abstract

In an attempt to produce the powdery mildew and black spot disease resistant rose plants (Rosa hybrida), we established an efficient inoculation system for precise evaluation of the resistance or susceptibility of rose cultivars to those diseases. In this system, the top leaflets of fourth trifoliate leaves generated from lateral buds of rose cuttings were used for inoculation with conidiospores of Sphaerotheca pannosa or Diplocarpon rosae. Two cultivars, “Paul's Pink” and “Magic”, were found to be strongly resistant to the powdery mildew pathogen and the “C line” of wild rose (R. multiflora) was highly resistant to both powdery mildew and black spot pathogens. These results suggest that the wild rose would be a useful gene source for providing a true disease resistance to commercially valuable cultivars of rose.