Abstract :
Fusarium eumartii is a fungus associated with declining
Quercus robur, in which it is found in the vessels. The
response of oak species to infection is known to vary:
Q. robur is susceptible, but Quercus cerris and Quercus
pubescens are resistant. An experiment was carried out
in 1996 and repeated in 1997, to examine how F. eumartii
colonization diered in oak species that were susceptible
or resistant to the fungus by counting the number of
vessels with mycelium at various distances from the
inoculation site in infected seedlings and by determining
the amount of viable fungus in infected tissue. Infected
vessels with mycelium were counted on sections (10 lm
thick) cut at 0, 2, 4, 6, 8 and 10 cm from the inoculation
site on 1-year-old inoculated seedlings as well as on
sections cut every 2 cm to the seedling tip. The amount
of viable fungus was determined by counting the colony
forming units (CFUs) in stem segments from the same
seedlings. Quercus robur seedlings had the greatest
number of infected vessels and the greatest number of
CFUs. Forty days after inoculation, the extent of
vertical fungal spread was 28.12 cm in Q. robur,
3.15 cm in Q. cerris and 3.00 cm in Q. pubescens. The
greatest number of CFUs was found in Q. robur at day 5
after inoculation. Analysis of variance con®rmed the
results.
