Structural Aspects of the Parasitism of Sclerotia of Sclerotinia sclerotiorum (Lib.) de Bary by Coniothyrium minitans Campb.

Sclerotia of Sclerotinia sclerotiorum inoculated with pycnidiospores of Coniothyrium minitans were studied by means of light microscopy and transmission and scanning electron microscopy. The hyperparasite penetrated the walls of the rind cells by means of physical pressure and destroyed the cell contents. Penetration of medullary hyphae was by enzymic lysis and physical pressure; there was evidence to suggest that the hyperparasite may coil around the host cells before inserting infection hyphae.