Interaction between Hymenoscyphus fraxineus and Phytophthora species on young Fraxinus excelsior seedlings

Abstract

Common pathogenicity tests on 16-month-old ash plants were performed using isolates of Hymenoscyphus fraxineus and three different Phytophthora spp. isolated under declining ash trees in Wolica Nature reserve in Poland. There were no statistically significant differences among the different inoculation treatments and lesion lengths averaged 1.67 cm. After analyses of inoculated roots, five out of 10 root parameters showed statistically significant differences, and after a Dun can's Multiple Range test, significant differences were found with control plants while there were no differences among the treatments. The largest root loss was with the treatment inoculated with both H fraxineus and P. plurivora (HF + PP), and both fine and total root lengths were 2.30 and 2.27 times smaller, respectively, than the non-inoculated control. The earliest mortality of young ash plants was observed also with the I IF + PP treatment. Results showed high aggressiveness of IL fraxineus to young ash plants, with indications that root infections with Phytophthora spp. may contribute to greater damage, but more research is needed to clarify the interaction between H. fraxineus and Phytophthora spp. in ash dieback.