Cellular Damage to Phytophthora infestans in Tomato Leaves Treated with Oxadixyl: an Ultrastructural Investigation

Ultrastructural observations showed massive accumulation of electron dense deposits adjacent to plasmalemma and mitochondria and mitochondrial degeneration, which probably leads to cell death, in some hyphae and haustoria of Phytophthora infestans in infected tomato leaves treated with the systemic fungicide oxadixyl (8 μg/ml). However, no changes in the endoplasmic reticulum and number of ribosomes were observed. The cell walls of some hyphae were markedly thickened after oxadixyl treatment. Degenerated haustoria were partly present in intact host cells. Evidently, fungal cell damage by treatment with oxadixyl is not correlated with host cell damage.