First Report of Diplodia sapinea P. Karst. on Pinus sylvestris L. in Central Siberia

On Pinus sylvestris L. trees of different ages with different phytopathological conditions, we have identified the invasive species Diplodia sapinea (Fr.) P. Karst., which is a dangerous pathogen of coniferous trees, for the first time in Central Siberia (in the parks of Krasnoyarsk). Pure cultures are isolated from pycnidia on cones; their morphological and molecular genetic characteristics correspond to the species D. sapinea. Siberian isolates are characterized by a high radial growth rate on nutrient media and are phytopathogenic against shoots of P. sylvestris and fruits of Granny Smith apples in vitro. They cause rapid and extensive necrotic lesions of the bark, shoot cambium, and fruit pulp and exhibit high peroxidase and protease enzymatic activity. Siberian D. sapinea isolates do not exceed the parameters of southern isolates in terms of morphological characteristics, enzyme activity, and phytopathogenicity. Significant differences are shown with the Dp1-23 strain of Diplodia seriata De Not isolated from pycnidia on the cones of Cupressus sempervirens L. For Siberian D. sapinea isolates, high resistance to cold stress is established in the temperature range from –8 to –31°C in a series of experiments on freezing-thawing of the mycelium. After activation, the radial growth rate of isolates on potato dextrose agar (PDA) at 24°C turn out to be higher than that of strains that were not subjected to freezing; relatively slow activation is noted at –16°C compared to other temperatures. The presence of a long endophytic phase in the species, which was discovered in Central Siberia for the first time; high adaptive capabilities; and phytopathogenicity pose a particular danger to its spread to a new territory and host plants. This requires special attention and study.