Differential Inhibition of Sphaeropsis sapinea Morphotypes by a Phenolic Compound and Several Monoterpenes of Red Pine

Abstract

The in vitro effects of a red pine phenolic compound (pinosylvin), a phenolic compound common to other species (tannic acid), and the major red pine monoterpenes (α-pinene, β-pinene, and δ-3-carene) on spore germination and mycelial growth of Sphaeropsis sapinea were examined. Two A and two B morphotype isolates were used. At 88 μg/mm2, pinosylvin inhibited spore germination of all four isolates (98 to 100%). At 8.8μg/mm2, spore germination of B isolates was inhibited more than that of A isolates (73 versus 30%). Pinosylvin also inhibited mycelial growth of B isolates more than that of A isolates (84 versus 13% at 88 μg/mm2). Tannic acid stimulated or had little affect on spore germination and had little affect on mycelial growth of either morphotype. Spore germination of B isolates was inhibited more than that of A isolates by β-pinene at saturation (79 versus 37%). Spore germination of B isolates was inhibited and germination of A isolates was stimulated by δ-3-carene below saturation (49 versus -7%). Mycelial growth of B isolates was inhibited more than that of A isolates by all monoterpenes at saturation. Differences observed between morphotypes below saturation were significant only for β-pinene. These results demonstrate the biological activity of a phenolic compound and monoterpenes that occur in red pine. The differential responses might provide means of distinguishing morphotypes and offer a potential explanation for ecological specialization.