VIEW ARTICLE

Histopathology of Calonectria crotalariae on Highbush Blueberry. R. D. Milholland, Associate Professor of Plant Pathology, North Carolina State University, Raleigh 27607; Phytopathology 64:1228-1231. Accepted for publication 23 April 1974. DOI: 10.1094/Phyto-64-1228.

The histological relationship of Calonectria crotalariae in infected blueberry leaves, stems, and roots was investigated. Penetration of leaf and stem tissue was primarily through stomates; however, direct penetration was observed. Appressoria were formed 8 h after inoculation and measured 5-6 µm in diam. Infection of succulent stems by C. crotalariae caused a complete breakdown of cortex and phloem tissue. Hyphae measured 1-5 µm in diam, and grew intracellularly in the vascular tissue of stems and roots. Death of blueberry plants is due primarily to the occlusion of the xylem elements by mycelia, gel deposits, and tyloses that impede or restrict the flow of water. Perithecial development is initiated in the stem cortex with the formation of a large stroma. The somatic hyphal cells push through the epidermis and give rise to the mature perithecium.