STUDIES IN THE GENUS CALICIOPSIS

Abstract

Three species of the genus Caliciopsis, all of which produce cankers on conifers, were investigated with respect to development, morphology, general biology, and pathogenicity. Caliciopsis orientalis is described as a new species. Developmental studies have shown that the ascocarps originate from the surface of an erumpent stroma. The female sexual structures are formed from dark-staining hyphae which arise in the core of the young ascocarp. Certain of these hyphae send out trichogynes which penetrate to the outside of the ascocarp. The hyphae enlarge greatly and produce clusters of ascogonia by a budding process or through meristogenous division of the hyphal cells. The ascogonia may further divide by septum formation and thus become multicellular. Septate, branching ascogenous hyphae grow out from the ascogonia and give rise to tufts of asci from the terminal cells. The stalks of the asci elongate enormously as they are carried up into the hymenium. Homologous development and structure were shown in several members of the Caliceaceae. Differences in the final appearance of the hymenium were attributed to the absence of extensive ascogenous hyphae in the Caliceaceae, but the fundamental similarities were interpreted as evidence of a phylogenetic relationship with Caliciopsis. Comparison of the asci, hymenium, and general habit of two genera of the Coryneliaceae with Caliciopsis confirmed the opinion of previous workers that the two groups are related. Observations on fruiting cycles revealed developmental correlations which indicated the possibility of functional spermatia, but experimental spermatization failed to prove this. Data on spore dissemination, germination, and penetration were also gathered. Canker anatomy and host–parasite relationships were elucidated. Pure cultures were obtained from both spermatia and ascospores. The latter were used to determine nutritional requirements of the fungus by measuring growth response to 14 carbon compounds, 5 nitrogen sources, and 7 vitamins. The effects of pH, temperature, and aeration on vegetative growth in pure culture were also studied. Extensive field observations revealed that one species (C. pseudotsugae) is widespread in British Columbia on three native conifers, and that in addition to primary pathogenicity it offers opportunities for associative effects to other forest pathogens which may result in serious damage. Behavior in pure culture confirmed the evidence of association between the pathogens involved. Pathogenicity was proved by extensive field inoculations.