Host-Parasite Relations of Phyllachora Species on Native Grasses

ABSTRACT

Hyphae of several species of Phyllachora on their respective hosts colonized grass leaf epidermal cells intracellularly, and hyphae darkened in these cells. The fungus grew intercellularly and intracellularly through the mesophyll to the opposite epidermis, which was then colonized in a similar manner. Hyphae remained separate and filamentous in mesophyll of cool-season grasses but was stromatic in fall collections of warm-season grasses. Lignified fibers above and below vascular bundles were colonized and displaced by hyphae. The clypeus was well developed prior to perithecium formation. Perithecia developed deep in the mesophyll and their growth increased thickness of leaves, relocated minor vascular bundles, and compressed adjoining vascular bundles. Vascular bundle sheath cells in cool-season grasses and all cells of the vascular bundle in warm-season grasses were colonized. No hyperplasia or hypertrophy of host tissue occurred.

Key Words:

• Phyllachora
• host-parasite relations
• Gramineae