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

Damm et al.
Cultures from the type material have not been preserved.
However, strain CBS 114.14 from Florida was deposited in the CBS
collection in Feb. 1914 by R.E. Clausen, as Gm. limetticola. The
strain was not specified as being an ex-type strain, and we suppose
that it was one of the samples requested by Clausen from wither
tip of lime in Florida. It is reasonable to consider the culture as
authentic material, and we therefore designate a dried subculture
as epitype for Gm. limetticola.
The wither tip disease of Citrus aurantifolia is apparently
identical with Key lime anthracnose (KLA), a specific disease of
leaves, twigs, flowers and fruits of Key lime (Citrus aurantifolia) and
has been well studied in recent years (Brown et al. 1996, Agostini
et al. 1992, Timmer & Brown 2000, Peres et al. 2008, MacKenzie
et al. 2009). While the causal organism of KLA was identified as C.
gloeosporioides by Agostini et al. (1992), following von Arx (1957)
who listed the fungus as a synonym of that taxon, Brown et al.
(1996) assigned the fungus to C. acutatum based on ITS sequence
data. According to Farr & Rossman (2012), Gm. limetticola has been
reported from Citrus aurantifolia in Barbados, California, Cuba, Fiji,
Florida, Hawaii, India, Jamaica, Philippines and Tanzania.
Colletotrichum strains from anthracnose on leaves of Key lime in
Florida, USA (KLA-Anderson, HM-1, Ss) and MTR-KLA-A1 (Belize)
included in the study of Peres et al. (2008) and MacKenzie et al.
(2009) have the same ITS and GAPDH sequences as strain CBS
114.14. Additionally, the ITS sequences of isolates DPI from Citrus
aurantifolia in Florida, USA (FN566877, Ramos et al. 2006) and c2
from Citrus sp. in Brazil (EU008878, Giaretta et al. 2010) match that
of CBS 144.14 with 100 % identity. Probable C. limetticola strains are
also included in Guerber et al. (2003) as mtDNA RFLP haplotype J3;
the GAPDH sequences of two Key lime strains (MD33, MD15) are
almost identical to that of CBS 114.14. The closest match with the
TUB2 sequence of strain CBS 114.14 with 100 % identity is GenBank
accession FN611029 from isolate DPI as well (Ramos et al. 2006). In
their study on Citrus in Portugal, Ramos et al. (2006) did not find any
C. acutatum s. lat.; C. gloeosporioides (s. lat.) seems to be the major
anthracnose pathogen.
According to MacKenzie et al. (2009), Key lime isolates differ
significantly from isolates from flowers of postbloom fruit drop
(PFD) affecting sweet orange (Citrus sinensis) in Florida, USA
(STF-FTP-10, OCO-ARC-4, ALB-IND-25). The differences are
found in their ITS, GAPDH and GS sequences. Based on ITS
and GAPDH sequences of 69 PFD and KLA strains from different
countries (Belize, Brazil, Costa Rica, Dominican Republic, USA
(Florida), Mexico), Peres et al. (2008) recognised the causal agents
of the two citrus diseases as two distinct phylogenetic lineages of
C. acutatum with few or no sequence differences in both the ITS
and GAPDH genes. We did not include PFD isolates in our study,
but according to ITS and GAPDH sequences, PFD and KLA strains
are related to each other, but seem to belong to different species.
Agostini et al. (1992) noticed morphological and cultural differences
between PFD and KLA isolates: appressoria of PFD isolates were
clavate and deeply pigmented and those of KLA isolates round,
smaller and less pigmented. Also, KLA strains grew slightly more
slowly than PFD isolates.
Pathogenicity tests by MacKenzie et al. (2009) had basically
the same results as those by Clausen (1912); only Colletotrichum
isolates from key lime caused leaf necrosis on key lime, while
isolates from PFD, strawberry (= C. nymphaeae, according to
this study), blueberry (= C. fioriniae, according to this study) and
leatherleaf fern did not. Key lime isolates caused necrosis of flowers
on Orlando tangelo flower clusters as well, but the percentage of
affected flowers was lower than those inoculated with PFD isolates.
Chen et al. (2005) identified a gene (KLAP1 gene) that was required
for causing KLA, particularly for the infection of Key lime leaves, but
not for the infection of flower petals.
Colletotrichum limetticola is distinguished from other species
by TUB2, GAPDH and HIS3, most effectively with TUB2, which
is only 2 bp different from the sequence seen in CBS 129823
(Colletotrichum sp. from Passiflora in Colombia, occupying an
unnamed subclade within Clade 1).
Colletotrichum lupini (Bondar) Damm, P.F. Cannon &
Crous, comb. nov. MycoBank MB800519. Fig. 18.
Basionym: Gloeosporium lupini [as Gm. lupinus] Bondar, Boln
Agric., São Paulo 13: 427. 1912.
≡ Colletotrichum lupini (Bondar) Nirenberg, Feiler & Hagedorn, Mycologia
94(2): 309. 2002, nom. inval. (Art. 33.3).
≡ Colletotrichum lupini var. setosum Nirenberg, Feiler & Hagedorn,
Mycologia 94(2): 309. 2002, nom. inval. (Art. 43.1).
Sexual morph not observed. Asexual morph on SNA. Vegetative
hyphae 1–6.5 µm diam, hyaline, smooth-walled, septate,
branched. Chlamydospores not observed. Conidiomata absent,
conidiophores formed directly on hyphae on the surface of
the medium and in the aerial mycelium. Setae not observed.
Conidiophores hyaline, smooth-walled, simple or septate and
branched, rapidly degenerating. Conidiogenous cells hyaline,
smooth-walled, cylindrical, 2.5–20 × 1.5–2.5 µm, often integrated
(not separated from fertile hyphae by a septum), opening 0.5 µm
diam, collarette 0.5 µm long, periclinal thickening visible. Conidia
hyaline, smooth-walled, aseptate, straight, rather variable in shape,
usually cylindrical to clavate with one end round and one end acute,
9–15(–26.5) × (3–)3.5–4.5(–6) µm, mean ± SD = 12.0 ± 3.2 × 4.1
± 0.6 µm, L/W ratio = 2.9, conidia of strain CBS 109221 are slightly
larger, measuring 11.5–15.5(–19) × (3.5–)4–4.5(–5) µm, mean ±
SD = 13.5 ± 1.9 × 4.3 ± 0.4 µm, L/W ratio = 3.2. Appressoria single
or in small dense clusters, medium brown, round to elliptical in
outline with an undulate to lobate margin, (4–)6–12(–20.5) × (4.5–)
6–9(–11.5) µm, mean ± SD = 9.0 ± 2.8 × 7.4 ± 1.7 µm, L/W ratio
= 1.2. Appressoria of strain CBS 109221 differ in being arranged
singly or in rows along hyphae and mostly having an entire margin
(rarely undulate to lobate).
Asexual morph on Anthriscus stem. Conidiomata acervular,
conidiophores formed on a cushion of pale brown angular cells
3–6.5 µm diam. Setae not observed in the ex-neotype strain,
but in strain CBS 109221 where a few setae were observed.
Conidiophores hyaline to pale brown, smooth-walled, septate,
branched, to 30 µm long. Conidiogenous cells hyaline to pale
brown, smooth-walled, cylindrical, sometimes ± inflated, 7–15
× 2.5–3.5 µm, opening 1–1.5 µm diam, collarette 0.5 µm long,
periclinal thickening distinct. Conidia hyaline, smooth-walled,
aseptate, straight, cylindrical to clavate with one end round and
one end acute, (10–)12.5–16(–18.5) × (3–)3.5–4.5 µm, mean ± SD
= 14.2 ± 1.7 × 4.0 ± 0.3 µm, L/W ratio = 3.6.
Culture characteristics: Colonies on SNA flat with entire margin,
hyaline, on filter paper and on Anthriscus stem partly covered with
short white to pale grey aerial mycelium, reverse of filter paper
white to pale luteous; growth 15–21 mm in 7 d (25–31 mm in 10 d).
Colonies on OA flat with entire margin; surface covered with felty to
woolly white to pale olivaceous grey aerial mycelium, reverse buff
to smoke grey; growth 15–19 mm in 7 d (24–27 mm in 10 d), strain
CBS 466.76 grows faster 23.5–27.5 mm in 7 d (36–37.5 mm in 10
d). Conidia in mass salmon.
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