Scanning-electron microscopy of infection of bean by species of Sclerotinia.

Scanning-electron microscopy was used to follow pathogenesis by Sclerotinia minor and S. sclerotiorum in bean tissue. The process of disease development included formation of infection cushions, mechanical penetration of the host cuticle, development of infection hyphae intercellularly beneath the cuticle and within the host cortex, interand intracellular development of ramifying hyphae that differed in size and appearance from infection hyphae, emergence of hyphae through host stomata, and formation of sclerotia on the host surface.