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

Damm et al.
Fig. 7. Colletotrichum cosmi (from ex-holotype strain CBS 853.73). A–B. Conidiomata. C–H. Conidiophores. I–N. Appressoria. O–P. Conidia. A, C–E, O. from Anthriscus stem.
B, F–N, P. from SNA. A–B. DM, C–P. DIC, Scale bars: A = 200 µm, B = 100 µm, C = 10 µm. Scale bar of C applies to C–P.
Culture characteristics: Colonies on SNA flat with entire margin,
hyaline, buff to pale honey, on filter paper partly pale olivaceous
grey, the medium, filter paper and Anthriscus stem partly covered
with floccose-felty whitish to pale olivaceous grey aerial mycelium
and orange acervuli, reverse of filter paper partly pale cinnamon,
pale olivaceous grey to olivaceous grey; growth rate 23–24 mm
in 7 d (33.5–34 mm in 10 d). Colonies on OA flat with entire
margin; surface entirely covered with thin floccose-felty white to
pale olivaceous grey aerial mycelium and orange acervuli, reverse
vinaceous buff, purplish grey to fuscous black; growth rate 23–25
mm in 7 d (33.5–37.5 mm in 10 d). Conidia in mass orange.
Material examined: Netherlands, Wageningen, from seed of Cosmos sp., collection
date and collector unknown (deposited in CBS collection in Nov. 1973 by G.H.
Boerema), (CBS H-20794 holotype, culture ex-type CBS 853.73 = PD 73/856).
Notes: Kwon et al. (1999) report C. acutatum (s. lat.) to cause sunken
brownish spots on stems, as well as symptoms on leaves, flowers
and floral axes of Cosmos bipinnatus in Korea. Morphological
characters (conidia, appressoria) are similar to those of strain CBS
853.73, except for setae, which our strain did not develop in our
standard culture conditions. It is therefore possible that the collection
from Korea represents C. cosmi. Colletotrichum acutatum (s. lat.) is
also known as an anthracnose pathogen of flowers and flower buds
of Cosmos bipinnatus in Japan (Yaguchi et al. 1996). The shape of
conidia and appressoria of the Japanese fungus are similar to our
strain, but the conidia are smaller, measuring 11–14 × 2.8–3.5 µm.
Two other species are reported from Cosmos bipinnatus in India, C.
truncatum (as C. capsici) associated with seeds and causing seed
and seedling rot (Srivastava et al. 1981) and C. gloeosporioides
associated with leaves (Kumari et al. 1981). When strain CBS
853.73 was first accessed into CBS, von Arx identified it as C.
gloeosporioides, but with the remark “deviating by longer, slender
conidia”. Molecular data do not support this identification; the strain
belongs to the C. acutatum complex, but it is possible that reports
of C. gloeosporioides refer to this species.
Colletotrichum cosmi is part of clade 2. It can be separated
from other species by all gene sequences, but mostly with only 1
bp divergence. There are more sequence divergences in GAPDH
and HIS3; however, with these genes individually, the species sits
within the very variable C. nymphaeae clade. The closest match
in a blastn search with the TUB2 sequence of strain CBS 853.73
(with 99 % identity, 4 bp differences) was GU246633 from isolate
R14 from Capsicum annuum from South Korea (Sang et al. 2011),
while the closest match with the GAPDH sequence covering ±
the full length sequence (with 98 % identity, 4 bp differences) was
HQ846724 from isolate OBP6 from an unknown plant, probably
from India (P. Chowdappa, C.S. Chethana, S. Madhura, unpubl.
data). We do not consider that these data in isolation are sufficient
evidence to identify these sequences as originating from C. cosmi.
There are 22 sequences in GenBank that match the ITS sequence
of strain CBS 853.73 with 99 % identity, all with 2 bp differences.
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