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

The Colletotrichum acutatum species complex
Fig. 18. Colletotrichum lupini (from ex-neotype strain CBS 109225). A–B. Conidiomata. C–I. Conidiophores. J–O. Appressoria. P–Q. Conidia. A, C, P. from Anthriscus stem. B,
D–O, Q. from SNA. A–B. Dissecting microscope (DM), C–Q. Differential interference contrast illumination (DIC), Scale bars: A = 100 µm, C = 10 µm. Scale bar of A applies to
A–B. Scale bar of C applies to C–Q.
Material examined: Ukraine, from seed of Lupinus albus, unknown date, H.I.
Nirenberg, culture ex-neotype of C. lupini, CBS 109225 = BBA 70884. Germany,
from Lupinus albus, unknown date, U. Feiler, culture ex-holotype of C. lupini var.
setosum, CBS 109221 = BBA 70352.
Notes: Two studies on the causal agent of lupin anthracnose
published in 2002 arrived at different results: while Talhinhas et
al. (2002) regarded the causal agent of lupin anthracnose as C.
acutatum, Nirenberg et al. (2002) concluded that the causal isolates
belonged to a separate species, C. lupini. Nirenberg and her
colleagues based this new name on Gloeosporium lupini (Bondar
1912), but their combination is invalid because the basionym was
not cited correctly according to the ICBN. We therefore validate
the combination here. Nirenberg et al. (2002) designated a dried
culture derived from BBA 70884 (= CBS 109225) as a neotype
of Gm. lupini, since no type material was designated by Bondar
(1912); this action is nomenclaturally correct.
Nirenberg et al. (2002) additionally described a variety of the lupin
pathogen, C. lupini var. setosum. They noted few morphological and
physiological differences between the two varieties: strains of var.
lupini were observed to produce more conidia than var. setosum in
the aerial mycelium, as well as to grow slightly slower on PDA and
to have a lower optimum growth temperature. In addition, var. lupini
isolates usually formed concentric growth rings in culture, while var.
setosum did not. The authors rarely observed setae in var. lupini,
but these were regularly seen in var. setosum. In our study, the
ex-holotype strain of C. lupini var. setosum formed a few setae.
Nirenberg and colleagues indicated that the ITS sequences of the
two varieties differ in only one base. Our study, based on analysis of
six genes, showed few other bp differences, blurring the distinction
between the two varieties. The name C. lupini var. setosum was
also invalidly published (Art. 43.1). As the species name C. lupini
was invalid itself at the time, and as we do not accept the variety as
a distinct taxon, we do not validate the name here.
According to Nirenberg et al. (2002), a typical feature of C.
lupini is the conidial morphology, with spores having one end
pointed and one rounded. We also observed this feature clearly
when the fungus was growing on Anthriscus stem. However, the
conidia of the ex-neotype strain observed in this study on SNA are
from simple or branched conidiophores at the agar surface and
from the aerial mycelium rather than from conidiomata, because the
strain no longer produces defined acervuli on this medium. Conidia
from aerial mycelium are ± cylindrical, sometimes with both ends
rounded. They are very variable in size (Nirenberg et al. 2002).
Colletotrichum lupini was originally described from Lupinus
albus in the São Paulo region of Brazil, presumably introduced
to South America along with its host plant, which is native to the
Mediterranean region (Kurlovich 2002). The only isolates from
South and Central America (Bolivia and Costa Rica) included in
our study have sequences identical to that of the ex-neotype strain
of C. lupini. The same is true for the strains studied from Europe
and elsewhere. The species now appears to have no restriction to
particular continents or climatic zones.
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