Geosmithia morbida sp. nov. a new phytopathogenic species living in symbiosis with the walnut twig beetle (Pityophthorus juglandis) on Juglans in the USA
Abstrakt
Widespread morbidity and mortality of Juglans nigra has occurred in the western USA over the past decade. Tree mortality is the result of aggressive feeding by the walnut twig beetle (Pityophthorus juglandis) and subsequent canker development around beetle galleries caused by a filamentous ascomycete in the genus Geosmithia (Ascomycota: Hypocreales).
Thirty seven Geosmithia strains collected from J. californica, J. hindsii, J. major, and J. nigra in eight USA states (AZ, CA, CO, ID, OR, UT, WA) were compared using morphological and molecular methods (ITS rDNA sequences). Strains had common characteristics including a yellowish color of conidia en masse, growth at 37oC, and absence of growth on Czapek-Dox agar and belonged to a single species described here as G. morbida.
Whereas Geosmithia are common saprobes associated with bark beetles attacking hardwoods and conifers worldwide, G. morbida is the first species documented as a plant pathogen.