Pathogenicity of wild-type and albino strains of the fungus Ceratocystis resinifera, a potential biocontrol agent against bluestain

Abstract

To verify the environmental innocuousness of large-scale applications of an albino strain (Kasper) of Ceratocystis resinifera Harrington & Wingfield, a potential biocontrol agent against bluestain, we tested the pathogenicity of this fungal species in greenhouse and field trials. In the greenhouse, the development of C. resinifera was negligible in deciduous seedlings, whereas the fungus was able to colonize the three conifer species tested. Ceratocystis resinifera induced only small lesions in white pine ( Pinus strobus L.) but colonized more extensively white spruce ( Picea glauca (Moench) Voss) and black spruce ( Picea mariana (Mill.) BSP) seedlings. Black spruce was the most affected species and showed the highest mean mortality rate (40%). However, the pathogenicity of C. resinifera seemed to be conditional, since no mortality was observed in one experiment. In the field trial, C. resinifera induced longer lesions than Ophiostoma piceae (Münch) Syd. & P. Syd. 1919 (a weak pathogen) as well as mortality in one mature black spruce tree. However, Kasper was less virulent than the wild type isolate tested, since it induced significantly smaller lesions and no mortality. In spite of its ability to colonize spruce trees, C. resinifera showed a weak tolerance to low oxygen levels, which, together with the lack of a primary bark beetle vector associate, may reduce its pathogenic potential.