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Histopathology and Pathogenicity of Botryosphaeria dothidea on Blueberry Stems. R. D. Milholland, Associate Professor of Plant Pathology, North Carolina State University, Raleigh 27607; Phytopathology 62:654-660. Accepted for publication 21 January 1972. DOI: 10.1094/Phyto-62-654.

Infection of blueberry stems by Botryosphaeria dothidea resulted from both wounded and nonwounded inoculation. Mode of penetration and stage of plant development influenced both the type and extent of disease development. Penetration of stems by the fungus through open stomata did not result in necrosis or dieback; instead, small raised lesions developed but failed to enlarge. The fungus was restricted to the outer portion of the lesion. Infection of succulent stems by B. dothidea through wounds resulted in a rapid breakdown of all tissues. As the fungus progressed down the stem, tyloses were formed causing partial or complete occlusion of the xylem vessels. In addition to tyloses, dark-stained protrusions of an undetermined nature were formed in infected woody stems. These protrusions originated from parenchyma cells adjacent to the xylem vessels in a manner similar to formation of tyloses. In a susceptibility trial, 10 highbush blueberry cultivars were highly susceptible to six isolates of B. dothidae, whereas eight rabbiteye blueberry cultivars were susceptible to only five.