Evaluation of antifungal activities of woody plant barks using an incubation system with Trametes versicolor

From the paper

Abstract

KEY MESSAGE: The novel incubation system where antifungal activities of bark tissues against Trametes versicolor were evaluated revealed that the inner bark of Sorbus commixta strongly inhibits mycelial growth of T. versicolor. Tree barks protect inside of tree bodies against pathogen invasion, but their chemical constitutive defense mechanisms remain largely unexplored. Therefore, the antifungal activities of bark tissues of 25 tree species acquired from Hokkaido, Japan, were examined to investigate the constitutive chemical defense mechanisms of tree barks. Bark pieces were placed on potato dextrose agar with Trametes versicolor after sterilization with gamma rays at 15 kGy. Bark tissues of most species exhibited limited activities. However, the whole and inner barks of Sorbus commixta completely inhibited the mycelial growth of T. versicolor. Furthermore, the inner bark of S. commixta on media with grooves also inhibited the mycelial growth of T. versicolor, indicating that antifungal substances generated from the inner bark of S. commixta are volatile. Among other species, Cerasus sargentii var. sargentii, Picea jezoensis var. jesoensis, and Magnolia obovate showed lower antifungal activities than S. commixta. We also examined the validity of 15 kGy for sterilizing the bark pieces of 16 species among 25 species. A dose of 12 kGy was sufficient to sterilize the bark pieces of all species, except Abies sachalinensis, and 15 kGy was necessary for the bark pieces of A. sachalinensis. In conclusion, this incubation system can be applied to select tree species, such as S. commixta, with high antifungal activities, and 15 kGy was sufficient for this incubation system to sterilize the barks of tree species in Hokkaido. This incubation system is useful to find out tree species that form bark tissues with unique chemical defense mechanisms.