Microscopic evidence for the hemibiotrophic nature of Diplocarpon rosae, cause of black spot disease of rose

The development of Diplocarpon rosae was not fully understood and reports on the mode of nutrition in its rose host were conflicting. This report describes the ultrastructure of D. rosae haustoria, and clarifies the developmental stages at which necrotrophic intracellular hyphae are formed. Evidence suggests that the mode of nutrition for this pathogen differs according to stages of its development and that D. rosae is a hemibiotroph. It has a biotrophic phase characterized by haustoria and a necrotrophic phase characterized by necrotrophic intracellular hyphae.