Field Resistance in Three Native Monocotyledon Species That Colonize Indigenous Sclerophyll Forest After Invasion by Phytophthora cinnamomi

Abstract

Lepidosperma laterale (Cyperaceae), Gahnia radula (Cyperaceae) and Poa sieberana (Poaceae) colonize bare ground of dry sclerophyll forest after disease due to P. cinnamomi. To determine their resistance, plants grown in divided root boxes were inoculated with 150-200 zoospores of the pathogen.

Infected roots ceased growth. In the small necrotic lesions produced, the pathogen remained viable and capable of providing a source of inoculum for disease extension. Fungal growth was usually limited to the lesion but in some cases a few hyphae were observed in adjacent tissue. Away from the lesion there was a rapid reduction of fungal material and of the associated cellular disintegration. Rates of root production and root growth were not stimulated by infection but uninfected lateral roots replaced the root tip in some plants; in others, a new root tip emerged from the necrotic zone, enabling the plant to outgrow the fungal attack.