Pathogenic Variation in Gremmeniella abietina Among Finnish Isolates : Shoot and Foliage Diseases in Forest Trees. Proceedings of a Joint Meeting of the Working Parties Canker and Shoot Blight of Conifers (S2.06.02) Foliage Diseases (S2.06.04)

Florenz

1995

S. 190-198

14 Lit. Ang.

Bandaufführung

77410

The pathogenic variation between types A and B of Gremmeniella abietina was supposed to exist according to preliminary experiments. Three types of experiments were established to test these differences in pathogenicity. In the first experiment conidia of Gremmeniella abietina isolates were sprayed in annual shoots of young Scots pine seedlings. The inoculation was carried out in August 1992 and the disease symptoms were assessed in June 1993. In two other experiments young Scots pines were inoculated with mycelium of isolates both in stems and annual shoots. The inoculations were made six times from August 11th to October 20th. Fourteen Finnish Gremmeniella abietina isolates, seven of both types, were used in the study. In the spring and early summer of 1993 the cankers in stems and necrosis in shoots were measured. Results show that 34.7% of pine seedlings sprayed with type A conidia were infected and 11.0% of seedlings sprayed with type B conidia were infected (control 1.4%). In mycelial inoculations into stems or shoots type A resulted in larger necrosis in phloem than type B. Type A was especially more pathogenic in shoot inoculations made in August. The size of necrosis increased from inoculations made in August to inovulations made in October. The results support the hypothesis that type A is more pathogenic in Scots pine than type B.