Effect of Incense—Cedar Heartwood Extract on Growth of Polyporus Amarus

Abstract

Heart rot fungi vary greatly in their ability to attack different tree species. Fomes pini (Thore) Lloyd and Polyporus schweinitzii Fr. have a broad host spectrum. Echinodontium tinctorium Ell. & Ev. has a more limited host range, and P. amarus Hedgc. is confined to a single host, incense-cedar (Libocedrus decurrens Torr.). This host specificity suggests (1) that the heartwood of incense-cedar meets the nutritional requirements of the fungus, and (2) that fungitoxic substances in the heartwood either are not effective against P. amarus or else are not present in sufficient quantity to inhibit it. In studies of such selective relations, in vitro growth tests of the fungus in host extracts are often used to detect the presence of growth-promoting substances or growthinhibiting substances or both. One approach to in vitro tests is to add the extract to nutrient media. The growth-promoting qualities of wood and wood extracts added to various media are well documented (La Fuse, 1937; Robbins and Hervey, 1955, 1959, 1960; Meyers and Reynolds, 1959; and others). Wall (1962) found that specific concentrations of cold water extracts of dead aspen branches added to agar stimulated spore germination of Fomes igniarius (L. ex Fr.) Kickx. The presence of fungitoxic sub? stances in heartwood has also been demonstrated by many workers. Rennerfelt and Nacht (1955) made a survey of the substances found in the heartwood of conifers and their toxicity to fungi. Anderson et al. (1963) made bioassays of the fungus-inhibiting extractive components of incense-cedar heartwood.