Susceptibility of different provenances ofPinus sylvestris, Pinus ContortaandPicea abiestoGremmeniella abietina

Summary In a randomized block factorial experiment, 1200 seedlings from four provenances, each ofPinus sylvestris, Pinus contortaandPicea abieswere inoculated with conidia (2 × 104and 1 × 106conidia/seedling) ofGremmeniella abietina (Brunchorstia pinea), isolated fromP. contortaplantations in northern Sweden. A further 600 seedlings were left as controls. The occurrence of symptoms and the extension of dead tissues on the annual shoots were recorded 13 months after inoculation. Only the higher spore dose resulted in significant infection.P. sylvestrisandP. contortaseedlings were equally susceptible (53% infected), and significantly more infected thanP. abiesseedlings (39%). The annual shoots ofP. sylvestrisandP. abieswere affected to 43% and 37% of their length, which was significantly more than 15% of the length of P.Contortashoots. The frequency of affected seedlings differed between the most southern and northern provenances ofP. sylvestrisandP. abies, and between the northwestern and the south‐eastern provenance of P.contortaTwenty‐six months after inoculation, a higher proportion ofP. contortaseedlings thanP. sylvestrisandP. abiesseedlings had recovered, and a lower proportion ofP. contortathanP. sylvestrisandP. abiesseedlings had died. This paper discusses whyP. sylvestriswas found to be more susceptible toG. abietinathanP. contortain this experiment, while the reverse is found in plantations in northern Sweden.