Colletotrichum: complex species or species ... - CBS - KNAW

Damm et al.
Fig. 4. Colletotrichum australe (from ex-holotype strain CBS 116478). A–B. Conidiomata. C. Seta. D–G. Conidiophores. H. Tip of seta. I. Basis of seta. J–K. Conidiophores.
L–Q. Appressoria. R–S. Conidia. A, C–G, R. from Anthriscus stem. B, H–Q, S. from SNA. A–B. DM, C–S. DIC, Scale bars: A = 100 µm, F = 10 µm. Scale bar of A applies to
A–B. Scale bar of F applies to C–S.
long, periclinal thickening distinct. Conidia hyaline, smooth-walled,
aseptate, straight, cylindrical, sometimes slightly constricted in the
middle, with one end round and one end slightly acute to truncate,
(16–)17–20(–22) × (4–)4.5–5(–5.5) µm, mean ± SD = 18.6 ± 1.6
× 4.7 ± 0.4 µm, L/W ratio = 4.0, conidia of strain CBS 131325
smaller, measuring (13.5–)15–17.5(–18) × (3.5–)4–5(–5.5) µm,
mean ± SD = 16.3 ± 1.1 × 4.4 ± 0.4 µm, L/W ratio = 3.7.
Culture characteristics: Colonies on SNA flat with entire margin,
hyaline to honey, filter paper straw to pale olivaceous grey, aerial
mycelium lacking, reverse same colours, growth rate 16–18 mm in
7 d (28.5–30 mm in 10 d). Colonies on OA flat with entire margin;
surface pale luteous to amber, in the centre covered with floccose
white aerial mycelium, reverse pale luteous to salmon, growth rate
16–20 mm in 7 d (25–29.5 mm in 10 d). Conidia in mass salmon.
Material examined: South Africa, Stellenbosch, university campus, from
Trachycarpus fortunei, 2 Jan. 1998, J.E. Taylor, (CBS-H 20721 holotype, culture
ex-type CBS 116478 = HKUCC2616). Australia, Western Australia, Alcoa, from
Hakea sp., 12 Jul. 2011, W. Gams, culture CBS 131325.
Notes: Colletotrichum australe belongs to the clade that includes
C. phormii, C. kinghornii, C. rhombiforme and C. acerbum. Setae
are better developed (in cultures on Anthriscus stem) and conidia
are larger than in most other species in the C. acutatum species
complex. Only C. phormii forms larger conidia, which are fusiform,
while those of C. australe are cylindrical. Additionally, appressoria
of C. australe are shorter than those of C. phormii. Conidia of C.
rhombiforme are shorter, while those of C. kinghornii are narrower.
It is possible that Fusarium hakeae (Hennings 1898), described
from leaves of Hakea saligna from the Botanic Garden in Berlin,
Germany, is the same species as C. australe. The description is
short but largely corresponds with our species, but bearing in mind
that most Colletotrichum species show a lack of host specificity,
there is no strong reason to equate the two taxa in the absence
of sequenceable material of F. hakeae. Wollenweber (1916)
transferred F. hakeae to Gloeosporium, and von Arx (1957,
1970) included the name as a synonym of C. gloeosporioides.
Bondarzeva-Monteverde et al. (1936) described a separate fungus
as Gloeosporium hakeae from greenhouses in St Petersburg; this
was reported to have straight to curved conidia and is unlikely to
be a synonym of Hennings’ fungus. Lubbe et al. (2004) published
C.acutatum f. sp. hakeae for isolates that caused a distinctive
disease of Hakea in South Africa; these have shorter conidia than
those of C. australe and group in C. acutatum s. str. Colletotrichum
acutatum has been reported from Trachycarpus fortunei in Australia
and Switzerland by Taylor & Hyde (2003); we do not know whether
these collections represent further records of C. australe.
Colletotrichum australe is separated from other species by all
gene sequences surveyed except for CHS-1, which is the same
as that of C. phormii, and most effectively separated by HIS3. The
closest match in a blastn search with the TUB2 sequence of strain
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