Virulence of two Finnish Gremmeniella abietina types (A and B).

摘要

Thirteen Finnish G. abietina isolates of types A and B were compared for differences in their virulence. Three kinds of inoculations were made: 1 with conidia on young Scots pine (Pinus sylvestris) seedlings and 2 with mycelia on the stems and shoots of young P. sylvestris trees. Inoculations with conidia were carried out in August 1992 and inoculations with mycelia were carried out 6 times between 11 August and 20 October, 1992. The experiments were evaluated in the late spring and early summer of1993. It was shown that there was a difference in virulence between the 2 types. In the conidial inoculations type A infected 34.7% and type B infected 11.0% of the inoculated seedlings. For mycelial inoculations with type A the mean canker (stems) andnecrosis (shoots) lengths were 19.3 mm and 8.6 mm longer, respectively, than with type B inoculations. In shoot inoculations there also was a clear difference between the 2 types in the number of such inoculations where no symptoms were observed. For type B shoot inoculations there was no fungal growth in 21.5% whereas for type A inoculations the figure was only 3.7%.