Secondary spread of Heterobasidion annosum in white fir
Matteo M. Garbelotto1
Slaughter, G; Popenuck, T; Cobb, F W; Bruns, T D.
Canadian Journal of Forest Research, v.27, n.5, (1997): 766-773.
Tree mortality caused by Heterobasidion annosum Fr. (Bref) in white fir
(Abies concolor (Gord. & Glend.) Lindl.) often appears in clusters;
symptoms in the infected trees include sapwood and heartwood decay in tree
holes and roots. Although the pathogen can spread from tree to tree
through root contacts, it is often confined to the initially infected
trees or stumps. We devised a field inoculation study to determine
comparative virulence of fungal isolates, rates and modes of fungal
colonization, preferential direction of fungal colonization, and effect of
root size on fungal growth in white fir roots. Fifty trees were inoculated
with eight H. annosum isolates, and sampled at 4 and 12 months.
Heterobasidion annosum caused purple-brown staining and incipient wood
decay within 4 months. Isolates from stumps were as virulent as isolates
from trees. Fungal colonization was less in smaller than larger roots.
Fungal colonization was greater in the proximal (towards the bole) than in
the distal direction. Most fungal colonization in the distal direction
occurred during the 4 months postinoculation, while colonization in the
proximal direction occurred throughout the year.
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