quence homology with known fungal L-tubulin genes. The
partial gene sequences obtained were composed of ¢ve
exons and ¢ve introns. The same number and arrangement
of introns and exons are found in homologous L-tubulin
gene fragments from ascomycetes such as the Colletotrichum
gloeosporioides TUB2 gene (GenBank U14138) as
well as the Aspergillus £avus (GenBank M38265) and Neurospora
crassa (GenBank M13630) L-tubulin genes. The
longer length of the Ceratocystis L-tubulin gene fragments,
about 450 bp, is attributed to longer introns. The L-tubulin
sequences from C. adiposa as well as published Ophiostoma
species have, in addition to shorter introns, one less
intron compared with Ceratocystis species. Comparison of
the deduced L-tubulin protein sequences showed that the
seven Ceratocystis species shared 98^100% sequence identity
with each other.
A branch and bound search of the aligned DNA sequence
data generated three most parsimonious trees,
one of which is shown in Fig. 1. Neighbor-joining analysis
using uncorrected (‘p’) distances produced a single tree
with topology similar to Fig. 1. C. adiposa was chosen
for the outgroup taxon because phylogenetic analysis
based on rDNA showed it to reside on a separate clade
from the other Ceratocystis species under consideration. A
step matrix that weighted transversions as three times
transitions did not have any e¡ect on tree topology. The
analysis identi¢ed two groups within the conifer associated
Ceratocystis species. A most parsimonious tree generated
using the ITS1/5.8S/ITS2 sequences also demonstrated the
same two groups within the conifer associated Ceratocystis
species [15]. C. resinifera and C. ru¢penni were closely
related and formed a single group. A second group was