Pathogenicity of five Verticicladiella species to lodgepole pine

Abstract

Pathogenicity of Verticicladiella procera, V. penicillata, V. abietina, V. serpens, and V. antibiotica was tested in live roots of field-grown lodgepole pine. The first four species produced resinous lesions varying in size according to species; expansion rates in root wood matched respective growth rates in culture. In root xylem, V. penicillata grew fastest, V. procera nearly as rapidly, producing lesions of various sizes, and V. abietina and V. serpens, slowest. Verticicladiella antibiotica was saprophytic. Diverse morphological structures, characterizing each species, were found in root wood. No dematiaceous hyphae occurred in roots inoculated with V. procera. However, fine hyaline hyphae, often anastomosing, penetrated axial tracheids and ray parenchyma. Verticicladiella penicillata produced abundant hyaline hyphae and few dematiaceous hyphae. Verticicladiella abietina produced buds on dematiaceous, septate, sporogenous hyphae in axial tracheids and ray parenchyma; hyaline hyphae also penetrated those cells. Verticicladiella serpens produced hyaline and dematiaceous pleomorphic structures from sporogenous hyphae in xylem cells. Results support speciation of five Verticicladiella isolates and demonstrate their pathogenicity to lodgepole pine.