Submitted to: Proceedings of the Mississippi Agricultural Pest Managment Joint Conference
Publication Type: Proceedings
Publication Acceptance Date: 2/19/2002
Publication Date: 3/15/2002
Citation: Lyman, M.R., Curry, K.J., Smith, B.J. 2002. The host-pathogen relationship between cercosporella rubi and balckberry (rubus sp.) cultivar 'shawnee'.. Proceedings of the Mississippi Agricultural Pest Managment Joint Conference.
Technical Abstract: Rosette disease of blackberry is characterized by the onset of rosettes in early spring that develop elongated floral buds and open flowers with pink, wrinkled petals and reddish sepals. Cercosporella rubi is usually found in these abnormal flowers, and its hyphae proliferate on floral buds throughout their development without penetrating host tissues. Vegetative and floral buds of the rosette susceptible blackberry cultivar 'Shawnee' were processed for resin infiltration and examined at light and electron microscopic levels. C. rubi was present from the initiation of floral differentiation until diseased flowers became senescent. There were no morphological differences between healthy and diseased floral buds up to 5.0 mm diameter other than the presence of C. rubi. Necrosis appeared as floral buds reached 6.0 mm diameter. Hyphae also proliferated on stamens and ultimately clogged the forming stomia. The mode of primary infection in the spring is uncertain since C. rubi was never observed in and was rarely isolated from vegetative buds of primocanes. Floricanes were examined as a possible source for the presumed teleomorph, Mycosphaerella. An unidentified species of Mycosphaerella has been found on dead floricanes. These studies indicated that C. rubi may obtain nutrients from blackberry using a combination of saprophytic and parasitic mechanisms.