Varieties of Verticicladiella Wageneri

Abstract

Ninety-eight strains of Verticicladiella wageneri Kendr., cause of black stain root disease on conifers, were isolated from species of Pinus, Pseudotsuga, and Tsuga across the known range of the pathogen in western North America. Examination of these strains (45 of which were examined in detail) resulted in recognition of three apparently host-specialized morphological variants. Mycelial pigmentation, presence or absence of a hyaline margin on advancing mycelia, growth rate at 25 C, capacity for conidiophore production, and presence or absence of a swelling at the apex of conidiophore stipes were used to delineate the variants. The variant isolated primarily from hard pines (Pinus ponderosa, P. jeffreyi and P. contorta) is described as V. wageneri var. ponderosa var. nov. The variants from pinyons (Pinus monophylla and P. edulis) and Douglas-fir (Pseudotsuga menziesii) are not consistently distinguishable from each other and are retained in V. wageneri var. wageneri.