environments, are the dominant group of bacteria found inside sclerotia (Nonoyama
et al. 2009), the interior of sclerotia may constitute a low-pH environment. Our
frequent isolation of O. pilicola, which prefers acidic environments, strongly suggests that it colonizes the insides of sclerotia formed by other fungi. Phialophora
finlandia (Jumpponen 2001) and Meliniomyces variabilis (Ohtaka and Narisawa
2008), which are both classified as dark septate endophytic (DSE) fungi, were also
isolated. Several DSE fungi have been reported to form sclerotia or microsclerotia
(O’Dell et al. 1993; Stoyke and Currah 1993; Wagg et al. 2008). In addition, seven
species of ectomycorrhizal fungi were isolated (Gyoerffyella rotula, Gyoerffyella
rotula, Hypocrea sp., Lecythophora mutabilis, Cryptosporiopsis ericae, Cadophora
sp., Helotiales sp.). No pathogenic fungi known to form sclerotia were isolated.
Although C. geophilum was detected by the clone library method, it was not isolated
with the culture method. To explain this disparity, we hypothesize that either the
sclerotia were no longer viable or that C. geophilum, due to its slow growth on
artificial media (LoBuglio 1999), was unable to compete with other species that had
colonized the interior of the sclerotia. We also cannot exclude the possibility that the
sclerotia were formed by a species other than C. geophilum.
2.3.2.3 Morphology of Sclerotia Formed by Isolates
When the isolates and C. geophilum AT353 were cultured on CMA, MMN, and 1/2
CMMY media, C. geophilum only formed sclerotia on MMN (Fig. 2.4a). In contrast,
isolates Sc-iso-f02, Sc-iso-f06, and Sc-iso-f11, which were assigned to the mycelium
radices atrovirens (MRA) complex (Fig. 2.3), formed sclerotia on all three media
(Fig. 2.4b–d). Although verification through inoculation experiments is required,
these isolates have been reported to be DSE (Jumpponen and Trappe 1998). These
three isolates formed especially high numbers of sclerotia on CMA: hyphae spread
over entire Petri dishes and began forming sclerotia at hyphal tips where further
growth was hindered. Greater numbers of sclerotia were formed as desiccation of the
media progressed.
Obase et al. (2014) isolated 297 C. geophilum isolates and 427 isolates of species
other than C. geophilum from 971 sclerotia. In contrast, Amasya et al. (2015) did not
detect T-RFLP peaks associated with C. geophilum. As mentioned above, in this
study, C. geophilum was detected by the clone library method but was not isolated
by the culture method. This result suggests that the sclerotia may have been formed
by species other than C. geophilum, including DSEs, or that many of the sclerotia
were inviable and degraded, which resulted to hinder DNA extraction.
2 Fungal Communities of Sclerotia Grains from Forest Soils
29
et al. 2009), the interior of sclerotia may constitute a low-pH environment. Our
frequent isolation of O. pilicola, which prefers acidic environments, strongly suggests that it colonizes the insides of sclerotia formed by other fungi. Phialophora
finlandia (Jumpponen 2001) and Meliniomyces variabilis (Ohtaka and Narisawa
2008), which are both classified as dark septate endophytic (DSE) fungi, were also
isolated. Several DSE fungi have been reported to form sclerotia or microsclerotia
(O’Dell et al. 1993; Stoyke and Currah 1993; Wagg et al. 2008). In addition, seven
species of ectomycorrhizal fungi were isolated (Gyoerffyella rotula, Gyoerffyella
rotula, Hypocrea sp., Lecythophora mutabilis, Cryptosporiopsis ericae, Cadophora
sp., Helotiales sp.). No pathogenic fungi known to form sclerotia were isolated.
Although C. geophilum was detected by the clone library method, it was not isolated
with the culture method. To explain this disparity, we hypothesize that either the
sclerotia were no longer viable or that C. geophilum, due to its slow growth on
artificial media (LoBuglio 1999), was unable to compete with other species that had
colonized the interior of the sclerotia. We also cannot exclude the possibility that the
sclerotia were formed by a species other than C. geophilum.
2.3.2.3 Morphology of Sclerotia Formed by Isolates
When the isolates and C. geophilum AT353 were cultured on CMA, MMN, and 1/2
CMMY media, C. geophilum only formed sclerotia on MMN (Fig. 2.4a). In contrast,
isolates Sc-iso-f02, Sc-iso-f06, and Sc-iso-f11, which were assigned to the mycelium
radices atrovirens (MRA) complex (Fig. 2.3), formed sclerotia on all three media
(Fig. 2.4b–d). Although verification through inoculation experiments is required,
these isolates have been reported to be DSE (Jumpponen and Trappe 1998). These
three isolates formed especially high numbers of sclerotia on CMA: hyphae spread
over entire Petri dishes and began forming sclerotia at hyphal tips where further
growth was hindered. Greater numbers of sclerotia were formed as desiccation of the
media progressed.
Obase et al. (2014) isolated 297 C. geophilum isolates and 427 isolates of species
other than C. geophilum from 971 sclerotia. In contrast, Amasya et al. (2015) did not
detect T-RFLP peaks associated with C. geophilum. As mentioned above, in this
study, C. geophilum was detected by the clone library method but was not isolated
by the culture method. This result suggests that the sclerotia may have been formed
by species other than C. geophilum, including DSEs, or that many of the sclerotia
were inviable and degraded, which resulted to hinder DNA extraction.
2 Fungal Communities of Sclerotia Grains from Forest Soils
29