Susceptibility of germinating seedlings of European and Eurasian populations of <i>Pinus sylvestris</i> to damping‐off caused by <i>Fusarium circinatum</i>

The effect of inoculation with <i>Fusarium circinatum</i> on survival of seed and seedlings of 19 populations of <i>Pinus sylvestris</i> was examined under environmentally controlled conditions, with four treatments (0, 50, 10³, 10⁶ spores ml^-1). A single seed source of <i>P. radiata</i> was included as a positive control. Germination (emergence of the plumule above the compost) and health of seedlings was assessed daily, for 85 days. Spore density had a significant effect on germination: at 50 spores ml^-1, only germination of a Northeast Scotland population was reduced. Treatment with 1000 spores ml^-1, however, reduced germination of six populations of <i>P. sylvestris</i> and of <i>P. radiata.</i> Survival of emerged seedlings also varied with inoculum dose. Approximately 75% of seedlings survived 85 days after germination after inoculation with 50 spores ml^-1. Seedlings of all populations were killed within 12-16 days of germination by the 10³ and 10⁶ spores ml^-1 treatments. Emerged seedlings of the Austrian populations showed the highest susceptibility to <i>F. circinatum</i> following treatment with 50 spores ml^-1, although 15% of seedlings of one Austrian population (AU3) survived to the end of the experiment (85 days after germination). There was no clear pattern in survival rates of the <i>P. sylvestris</i> seedlings from other populations treated with 1000 or 1 million spores ml^-1 due to death of all emerged seedlings within a short period. Variations in susceptibility of different populations of <i>P. sylvestris</i> to <i>F. circinatum</i> may be used in future selection and breeding programmes to reduce the impact of the pathogen as it spreads over wider areas in Europe and Eurasia.