Phenoloxidase and Peroxidase Activities in Zone Lines ofPhellinus Weirii

Abstract

SUMMARY Phenoloxidase and peroxidase were extracted from pigmented zones (zone lines) which were formed on agar media between two Phellinus weirii isolates or by one P. weirii isolate in response to the presence of an antagonist. Activity of enzymes from zone lines was compared with that of enzymes from mycelial tissues adjacent to the zone lines by isoelectric focusing on polyacrylamide gels. Zone lines produced stronger phenoloxidase and peroxidase reactions than did adjacent tissues. At least three phenoloxidases and as many as six peroxidase isozymes were detected in zone lines, some of which may have been induced or caused by the antagonists. Phenoloxidase and peroxidase were observed also in the zone lines formed by P. weirii in colonized Douglas-fir wood, but not in adjacent tissues. Phellinus weirii (Murr.) Gilbertson is a destructive root pathogen of conifers in northwestern United States and southwestern Canada. In cultures, confronted isolates of this fungus from separate infection centers develop a darkly pigmented zone line at their interface. The zone line is a distinct narrow dark line, representing a sheet of fungal mycelium composed of characteristic swollen hyphal cells. Childs (1963), who first recorded the phenomenon in P. weirii, used the term 'line of demarcation' and called the paired isolates forming these lines clones of the species. Pigmented zone lines also can be formed by P. weirii on agar media or in P. weirii-colonized wood in response to some antagonistic microorganisms. Zone lines appear to enhance P. weirii survival in colonized wood by excluding antagonists (Nelson, 1964, 1975). Kuwana (1958) found that cell fusion between different strains of Neurospora crassa Shear and Dodge that normally do not produce phenoloxidases leads to induced phenoloxidase activity and pigment formation. Hiroth (1965) reported that interactions at the interface between different isolates of Phellinus tremulae (Bond.) Bond. et Boriss, resulted in induction of weak phenoloxidase activity and pigment