Stilbene glucoside levels and the resistance of Sitka spruce (Picea sitchensis) tissues to colonization by root- and butt-rotting fungi

The relationship between constitutive stilbene glucoside (astringin and isorhapontin) levels in Sitka spruce (Picea sitchensis) bark and resistance of these tissues to colonization by the root- and butt-rot fungi Heterobasidion annosum and Phaeolus schweinitzii was determined in vitro in excised bark tissues. Two experimental systems were developed. In one, 15-mm-diameter bark discs taken from mature forest trees were challenged with mycelial cultures of the fungi; in the other, 70- or 100-mm lengths of stem, up to c. 30 mm diameter, were similarly challenged at the lower cut end. The extent of fungal colonization or necrosis in the challenged tissues was determined. The results indicated that both systems were capable of detecting differences in bark susceptibility to colonization between individual trees. No consistent correlation between stilbene levels and resistance to colonization by either fungus was found.