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Occurrence, Anatomy, and Morphology of “Blisters” on Cocoa Seedlings Inoculated with Crinipellis perniciosa. S. Dabydeen, Plant Science and Biochemistry, The University of the West Indies, St. Augustine, Trinidad. T. N. Sreenivasan, Cocoa Research Unit, The University of the West Indies, St. Augustine, Trinidad. Plant Dis. 73:481-484. Accepted for publication 15 June 1988. Copyright 1989 The American Phytopathological Society. DOI: 10.1094/PD-73-0481.

Cocoa seedlings inoculated with Crinipellis perniciosa exhibited blisterlike swellings and exudations in addition to the typical symptoms associated with witches’-broom disease. Studies using electron and light microscopy revealed that blisters were formed as a result of abnormal cortical growth induced by the pathogen. The rupturing of blisters resulted in desiccation, necrosis, and brown discoloration of the exposed cells. The exudation was not associated with the disintegration of host tissue and was probably due to the high internal pressure generated by hyperplasia and hypertrophy of infected tissues. Newly formed cells of the infected tissue did not form plasmodesmata in the cell walls.