Histopathological studies on corn downy mildew caused by Sclerospora maydis (Rac.) Butl

Histopathological studies on the corn plants inoculated with Sclerospora maydis were carried out to confirm the existence of the fungus in the apical meristem in relation to the systemic infection of the host plant. The hyphae were found in the central meristem of the shoot tip 20 days after inoculation. The hyphae were detected in every part of the corn shoot except for the apical meristem (in a narrow sense) but not in the root. The hyphae consisted of two types: slender and crooked hyphae. The slender hyphae were found in every infected tissue, and the crooked hyphae were observed only in the tissue of the expanded leaf showing systemic symptoms. Intercellular spaces of the diseased tissues in the expanded leaf were mostly occupied by crooked hyphae.