全 文 ：The Edible Truffle Choiromyces venosus
and Its Use in Sweden
Wedén Christina1
?
, Larsson Sonny2 , Burman Robert1 , Backlund Anders1
(1 Div . of Pharmacognosy, Dept . of Medicinal Chemistry, Uppsala University, Box 574 , SE-751 23 Uppsala, SWEDEN;
2 J odrell Laboratory, Royal Botanic Garden, Kew, Richmond, Surrey, TW9 3AB , UK )
Abstract: The ascomycete truffle Choiromyces venosus is still largely unknown with respect to its biology, ecology and
physiology . C . venosus has been collected and consumed as a delicacy in Sweden for at least 100 years . The specieswas
first described by Fries in 1830 , and has been regarded synonymouswith C. meandriformis, described by Vittadini 1831 .
In southern Europe there is a widespread belief that C . venosus is toxic to humans, but no record of C. venosus poisoning
has ever been reported fromnorthern Europe . Whether there is a taxonomic?phylogenetic explanation underlyingthe differ-
ent traditions in different parts of Europe is currently under investigation . Our studies in this field includecytotoxicity data
and are under completion . This is a highly important aspect in the attempts to establish a new cash crop . Preliminary re-
sults indicatethat the amounts of C. venosusextract required to achievecell death in the cytotoxicity assay is similar to that
of other commonly consumed fungi including Agaricus bisporus and Tuber aestivum .
Key words: Choiromyces; Tuber aestivum; Tuber mesentericum; Truffle; Cytotoxicity; Taxonomy; Systematics; Ecology
CLC number : Q 938 Document Code : A Article ID : 0253 - 2700 (2009 ) Suppl .ⅩⅥ - 094 - 03
Introduction
Choiromyces venosus in Sweden
The truffle Choiromyces venosus ( Fig. 1 ) , has a
history of being collected and eaten as a delicacy in
certain parts of Sweden during the last century ( Ro-
mell , 1907) . The main areas of collection are situated
around lake systems in the counties of the southeastern
parts of Sweden ( Fig. 2) . Already in the early 1900s
there wereplans to cultivate C . venosus inSweden, but
lack of understanding of its mycorrhizal life cycle
deemed these trials to fail ( Romell , 1906 ) . In most
reported cases, C. venosus has been encountered dur-
ing the summer months June-August, mostly in well-
managed lawnswhere the fruit bodies, or truffles, have
been spotted protruding through the soil surface . These
truffles have been rather large in size, not uncommonly
the sizeof a fist, with ascent that has varied fromvery
faint to pleasant and aromatic through and further to
nauseating . These different appreciations supposedly
reflect fruit bodies with a range fromimmaturespores to
mature spores and finally degradation, respectively .
The mature truffles are regarded as adelicacy and have
been used fresh, for examplemixed with butter-a com-
mon preparation also for the Burgundy truffle, Tuber
aestivum-thus ensuring a full preservation of volatile,
lipophilic compounds contributing to the complex aro-
mas . In addition, C . venosushas also inmany instanc-
es been consumed fried, opening a different aspect of
aromas . For longer storage it has been preserved deep
frozen or dried .
Comparing Choiromyces venosus with the genus Tuber
During the last decade the Burgundy truffle Tuber
aestivum ( syn . Tuber uncinatum) ( Wedén et al. ,
2005) has been discovered to growwell distributed over
the Swedish islands of Gotland and ?land ( Wedén,
2004; Wedén et al. , 2001; Wedén et al. , 2004 ) .
However, unlike C. vensosus, there is no record that
Tuber aestivumhas ever been used and appreciated as
a source of food or delicacy in Sweden, or even that its
occurrence has been reported prior to 1978 (Sunhede,
1978) . Despite this apparent lack of ethnographic trac-
es, preliminary results show that Tuber aestivumproba-
bly has been introduced to theSwedish islands at a sim-
ilar time as the re-colonization of the first mycorrhizal
云 南 植 物 研 究 2009 , Suppl . ⅩⅥ : 94～96
Acta Botanica Yunnanica
? ?Author for correspondence; E-mail : Christina.Weden@ebc.uu. se; Tel : + 46 18 471 4927; Fax: + 46 18 50 91 01
Fig . 1 Fruit bodies of Choiromyces venosus from Sweden .
Photo: Christina Wedén
Fig . 2 Map of Europe with the Swedish regions of naturally occurring
Choiromyces venosus ( lined, orange) and Tuber aestivum (filled, orange)
marked out . Choiromyces venosus has only been found on mainland Swe-
den, while Tuber aestivumhas only been found on the Swedish islands of
Gotland and?land . Illustration: Anders Larsson .
tree, Corylus avellana, after the last glaciation some
9000 years ago . Tuber aestivum is today a well-known
species which is collected and sold commercially also in
Sweden . In atimespan of 10 years from1999 to2008 ,
circa 6000 tree seedlings inoculated with Swedish Tu-
ber aestivum have been planted in truffle orchards on
the islands of Gotland and?land, as well as on the
Swedish mainland ( Wedén et al. , 2009 ) . In 2005 ,
the first cultivated truffle was harvested in Sweden,
only six years after establishment of the truffle orchard
(Wedén et al. , 2007 , 2009 ) . In addition to Tuber
aestivum, also theBagnoli truffle, Tuber mesentericum,
is known from the Swedish islands, where it was first
reported in year 2000 ( Wedén et al. , 2001 ) . Al-
though an appreciated delicacy in some regions of Italy
and France, Tuber mesentericum has not yet estab-
lished its commercial use in Sweden . It has a strong
naphthalene-like smell at full sporematurity discourag-
ing ingestion, but only very light heating duringprepa-
ration in combination with fatty milk products will re-
move thesevolatilesubstances and leaveapleasant aro-
matic taste similar to that of Tuber aestivum .
This contrast in traditional knowledge between
these truffles is surprisingas Tuber aestivumand T . m-
esentericumare well known delicacies and fungi docu-
mented in literature for centuries-both species until re-
cently unreported fromSwedish territory . While on the
other hand Choiromyces venosus, still comparably un-
known with respect to biology, ecology and physiology,
has been known and consumed as adelicacy in Sweden
for at least 100 years .
Although a true truffle ( i . e . ahypogeous ascomy-
cete dispersedby animal vectors) , C. venosus isknown
to often protrude, at least partly, through the soil sur-
face at maturity . This could be one explanation to why
it has been collected and consumed, while the com-
pletely hypogeous Tuber aestivumhas not . As the tra-
ditional Swedish kitchen does not encompass truffles
there has not been any known previous use of trained
pigs or dogs with the purpose to find truffles . Further-
more, the Tuber aestivumseason in Sweden is also pri-
marily in October and November, a time period when
little farming activity is undertaken in the forest mead-
owlands, which is the common Tuber aestivumhabitat .
C. venosus on theother hand has fruit bodies develop-
ing to maturity already during the summer months of
June to August, during the summer holidays when
many Swedish people spend time in their gardens,
where C . venosus is commonly found .
Choiromyces venosus nomenclature
C. venosus nomenclature is complicated, and the
species was first described by Elias Fries in 1830 , un-
der the name Mylitta venosa ( Fries, 1831) . In 1831
the Italian mycologist Carolo Vittadini describes the
59增刊ⅩⅥ Wedén Christina et al. : The Edible Truffle Choiromycesvenosus and Its Use in Sweden
genus Choiromyces with a species called C. me-
andriformis ( Vittadini , 1831 ) . To this genus is later
an additional species added, C . venosus, moved from
Mylitta and thus recombined . C. meandriformis and
C. venosus have been regarded as synonyms of the
same species, and in southern Europe C. me-
andriformis is themost commonly used name (Montec-
chi and Sarasini , 2000) . This assumption of synonymy
has been basedon the similarity in fruit body and spore
morphology, but not yet tested withmolecular tools . At
one point Elias Fries referred to C. venosus as Terfezia
leonis ( desert truffle) , to which it may have some
macroscopic resemblance ( Fries 1860 - 1866 ) . Even
today confusion regarding C . venosus persists and the
species is occasionally-whereas based on ignorance or
fraud-marketed as“white truffle”, thus confusing it
with the exceedingly expensive white Italian Alba truf-
fle, Tuber magnatum . Phylogenetically, Choiromyces
is moreclosely related to Tuber, than to Terfezia (Per-
cudani et al. , 1999) .
The reputed toxicity of Choiromyces venosus
There is a widespread belief that C . venosus is
toxic to humans . In mushroom books and field guides
from southern Europe, e.g . Italy and France, it is
listed as toxic leading to gastrointestinal problems . In
Spanish literature it is sometimes regarded as edible,
sometimes not, while in Hungary it is regarded as edi-
ble . No record of C. venosus poisoning have ever been
reported from northern Europe, where C. venosus is re-
garded as adelicacy in e.g . Sweden and Germany (hence
the commonGermanname Kaiserpilz) .Whether thereis a
taxonomic?phylogenetic explanation underlying the differ-
ent traditions in different parts of Europe is currently un-
der investigation . One possible explanation lies in a con-
fusion regarding themeaningof the scientific species epi-
thet venosum . While in some aspects being similar to the
English word venomous, the Latin word venosum should
be interpreted as venous or veined, referring to the mor-
phology of thegleba .TheLatin translationof venomous is
instead venenosum .Our studies inthis field includecyto-
toxicity data and are under completion ( Wedén et al. ,
unpublished data) . This is a highly important aspect in
the attempts to establish a new cash crop .
Results and Discussion
With regard to thestudiesof cytotoxicity, prelimi-
nary results indicates that the concentration of Swedish
C. venosus extract required to achieve cell death is
similar to that of other commonly consumed fungi in-
cluding Agaricusbisporus and Tuber aestivum ( Wedén,
unpublished data) . Ecological observations reveal a
broad vector range of organisms to which C . venosus
poses no apparent and immediate threat . These include
various species of slugs ( Mollusca) , flies ( Insecta) ,
birds (Aves) and roe deer (Mammalia) . With regard
to flies, observations have even been made ( Wedén,
unpublished data) where eggs havehatched and devel-
oped fromlarvae toadult flieson consumptionof C. ve-
nosus alone .
At the scientific symposium Forum fungorum in
the fall of 2007 , several exhibitors participated . A
number of thesewere producers of foodstuff and at least
two companies displayed and served preparations of
C. venosus with no immediateand apparent harmtothe
consumers (Backlund, personal observation) .
Hence, preliminary resultsof thestudies of Swed-
ish specimen of C. venosumsupport theview that these
appear to show a low degree of toxicity . Experiments
arenow expanded to investigate the genetic structureof
the species, as well as parallel studies of toxicity of
specimen from the southern part of the distribution
range .
Acknowledgements : This study has been financed by theSwed-
ish Research Council for Environment, Agricultural Sciences and
Spatial Planning (Formas project 2005 - 1177) .
References:
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gar f?r?r 1830 , Stockholm
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skaps-Akademien, Stockholm
Mont ?ecchi A , Sarasini M, 2000 . Funghi Ipogei d′Europa . AMB Fondazi-
one, Trento
Perc ?udani R , Trevisi A , Zambonelli A et al. , 1999 . Molecular phyloge-
nyof truffles ( Pezizales: Terfeziaceae, Tuberaceae) derived from nu-
clear rDNA sequence analysis [ J ] . Molecular Phylogeneticsand Evo-
lution, 13 : 169—180
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