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Introduction
Wild edible fungi have traditionally been used as
food or medicine worldwide (Boa, 2004). Some of
them —mostly saprotrophic— are cultivated (e.g. Aga-
ricus bisporus), while many others are exclusively
harvested in forests. Truffles are one of the few cultiva-
ted mycorrhizal fungi: they make part of the rural
European culture, and nowadays they are widely used
in international haute cuisine.
The term “truffle” is sometimes used to name all
hypogeous mushrooms in general, but it specifically
refers to the genus Tuber. Bonito et al. (2010) report
at least 180 species of Tuber around the world, although
only about 13 have commercial interest (Bonito et al.,
2009). The quintessential truffles are the European
black truffle (Tuber melanosporum Vittad.) and the
Italian white truffle (Tuber magnatum Pico).
T. melanosporum was first cultivated in France
during the 19
th
century (Olivier et al., 1996) and it is
currently cultivated worldwide (mainly in regions with
Mediterranean-like climate). Despite research efforts
cultivation is not completely domesticated. More re-
cently, other Tuber species have also been successfully
cultivated, such as Tuber aestivum Vittad. and its form
uncinatum, Tuber borchii Vittad. and the Tuber in-
dicum complex (Wang et al., 2006) (Chevalier and Fro-
chot, 1997; Zambonelli et al., 2000; Hu et al., 2005),
whereas the attempts to grow the native North Ameri-
can Tuber species are in their first stages (Lefevre,
2012). Much effort has been devoted to T. magnatum,
although without success (Gregori, 2007; Bencivenga
et al., 2009).
This review focuses on the current extent of T. mela-
nosporum cultivation, which is by far the most wide-
spread. We describe its potential socioeconomic impact,
the way in which the current situation has been achie-
ved and finally the knowledge needed for its progress.
Socioeconomic and environmental
values
Economic value
In France, Italy, Spain and Australia truffles are
currently a multi-million euro industry. In the first
Black truffle cultivation: a global reality
Santiago Reyna
1
* and Sergi Garcia-Barreda
1, 2
1
ETS Ingeniería Agronómica y del Medio Natural. Universidad Politécnica de Valencia. Cno. de Vera, s/n.
46022 Valencia, Spain.
2
Fundación Centro de Estudios Ambientales del Mediterráneo (CEAM).
C/ Charles Darwin, 14. Parque Tecnológico. 46980 Paterna (Valencia), Spain
Abstract
Aim of study: In recent decades the cultivation of the black truffle Tuber melanosporum has expanded across all the
Mediterranean-climate regions, but also to other regions outside the European standard for the species. We aim to
describe the current extent of T. melanosporum cultivation.
Area of study: Tuber melanosporum plantations in Europe, the Mediterranean basin, Australia, New Zealand, China,
America and South Africa.
Material and methods: The socioeconomic impact of T. melanosporum cultivation, the way in which the current
situation has been achieved and the knowledge needed for its progress are reviewed.
Research highlights: T. melanosporum has been successfully cultivated in several countries outside its natural area,
but many practices are still empirical and thus yields cannot be guaranteed. The recent advances in molecular techniques
and genome science are helping to overcome some of the difficulties traditionally constraining truffle research. The
role of truffles as a transitional element between agricultural and forestry activities makes its cultivation a paradigm
of sustainable rural development.
Key words: Tuber melanosporum; Europe; Australia; New Zealand; Chile; USA.
* Corresponding author: sreyna@agf.upv.es
Received: 23-07-13. Accepted: 12-12-13.
Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria (INIA) Forest Systems 2014 23(2): 317-328
Available online at www.inia.es/forestsystems ISSN: 2171-5068
doi: http://dx.doi.org/10.5424/fs/2014232-04771 eISSN: 2171-9845
318 S. Reyna and S. García-Barreda / Forest Systems (2014) 23(2): 317-328
three countries, truffles are harvested not only in
planted truffle orchards (cultivated truffles) but also
in natural forests (wild truffles). The value of the T.
melanosporum production is estimated to be around
20 million euro per year in France (Escafre and
Roussel, 2006), 7.5 million euro in Spain (estimated
for the past decade on the basis of the mean prices at
Vic market, in north-eastern Spain), and 4 million euro
in Australia in 2012 (Duell, 2012). In Italy the
production value of all species of Tuber together was
estimated to be 18 million euro in 1999 (Pettenella
et al., 2004).
The price that farmers receive for T. melanosporum
in Europe ranged in the past decade from less than 150
to more than 800 euros kg
–1
. The price for retail cus-
tomers can be much higher: e.g. in Paris and London
prices higher than 2000-4000 euros kg
–1
can be achie-
ved. This fact has encouraged truffle growers to sell
directly to restaurants and to use retail e-commer-
ce. In Australia the mean price in 2012 for the
higher quality class was about 950 euros kg
–1
(Duell,
2012).
The high price of T. melanosporum makes its
cultivation an interesting enterprise for farmers where-
ver suitable environmental conditions exist. A review
of economic evaluations of truffle plantation in Europe
by Bonet and Colinas (2001) showed that the internal
rate of return (i.e. the interest yield expected from the
investment) was always above 9%, although the return
time of the investment was longer than 10 years. The
GET (2002) estimated that markets would be able to
absorb around 1,000 t of T. melanosporum, which
represents more than ten times the current production.
In Spain its current discounted value has increased at
an annual rate of 3% over the past 50 years (Reyna,
2007b).
The total economic impact includes not only fresh
truffles sold by farmers, but also agritourism, local
mycological gastronomy, production of value-added
truffle products, truffle fairs and retail markets,
increase in agricultural land price in truffle-growing
regions, production of mycorrhizal seedlings in nur-
series, dog training, consumption of agricultural sup-
plies by truffle growers, technical assessment services,
etc. The total economic impact of T. melanosporum
was estimated to be around 70 million euros per year
in France (Escafre and Roussel, 2006). In Italy, the
total economic impact of all Tuber species together
was estimated to be more than 100 million euros (Gre-
gori, 2013).
Social value: rural development
In many T. melanosporum-producing regions of the
Mediterranean basin the environmental conditions and
the small size of plots limit the yield of traditional agri-
cultural crops (Pinto-Correia, 1993). Truffle cultivation
represents an alternative for their agriculture: an eco-
nomic diversification and an extra income. When non-
agricultural activities are brought into play (e.g. agri-
tourism) truffle fulfils a more robust role in rural
development. Besides, maintaining marginal agri-
cultural lands cultivated helps to preserve the tradi-
tional Mediterranean agroforestry landscapes and rural
population.
The harvesting of wild T. melanosporum also plays
a role in the rural economy of Italy and Spain. The
value that truffles add to forests is particularly inte-
resting in Mediterranean forests: given their low pro-
ductivity (Domínguez-Torres and Plana, 2002) it could
promote involvement of the rural communities in forest
protection and management.
In Italy and France truffles are a part of the rural
cultural heritage and a reason for pride. Truffle has
encouraged the development of partnerships and as-
sociations of growers, municipalities (such as the
Italian Città del Tartufo) and gourmets. Ecomuseums
such as those in Sorges (France), San Giovanni d’Asso
(Italy) and Metauten (Spain) introduce the public to
the various aspects of truffles.
Environmental value
In its natural area, T. melanosporum can be grown
with low environmental impact: the use of machinery
and chemicals is limited, so it can be easily considered
organic farming. Soil tilling of these plots increases
water infiltration rates. The maintenance of soil con-
servation structures limits soil erosion risk in steep
slopes. The use of native Quercus as host plants contri-
butes to the conservation of natural forests. In the fire-
prone Mediterranean landscapes, T. melanosporum
plantations constitute excellent firebreaks due to low
plantation densities, soil tilling and the herbicidal
effect of the fungus.
The history of truffle cultivation
Hypogeous fungi (most probably desert truffles of
the genera Terfezia and Tirmania) were consumed in
Black truffle cultivation: a global reality 319
the Antiquity by Mesopotamics, Egyptians, Greeks and
Romans. During the Middle Ages they are scarcely
cited in Europe, but in the Renaissance truffles gained
a reputation in Italy and France, and truffle consump-
tion spread among wealthy people (Reyna, 2007a).
Manna (2005) reports harvest regulations in Italy du-
ring this period. Ceccarelli wrote a monograph on the
management of wild truffières in 1564 (Granetti, 2005).
During the 18th and 19th centuries the consumption
of truffles increased thanks to gourmets such as Brillat-
Savarin. This encouraged the spreading of truffle
harvesting and the management of wild truffières. A
major advance occurred in the early 19th century when
the French farmer Joseph Talon had the idea of sowing
acorns from truffle-producing trees near or inside the
truffières. Auguste Rousseau disseminated the techni-
que and thousands of hectares of oaks were planted
thanks to this idea, boosted by the French reforestation
laws of 1860 and 1882 (Diette and Lauriac, 2005) and
the expansion of available agricultural land due to the
widespread vineyard destruction by the Phylloxera
plague (Olivier et al., 1996). This resulted in the golden
age for truffle production, with estimated productions
of 1,588 t in 1868, and 2,000 t in 1892. In Italy, Mat-
tirolo and Francolini also promoted reforestations to
increase truffle production (Granetti, 2005). In those
decades De Bosredon, Chatin and Pradel wrote mono-
graphs on truffle ecology and cultivation. During the
same period Carlo Vittadini provided the first detailed
morphological descriptions of many Tuber sporocarps
and a classification system (Trappe et al., 2009).
In the 20th century French production sharply de-
clined to the current 10-60 t per year, due to the rural
depopulation caused by the two World Wars and by the
rural to urban drift. The forest stand density increased
and much of farmers’ empirical knowledge was lost
(Olivier et al., 1996). In Italy the decline was not so
severe and it is limited to the first half of the century
(Manna, 1990). In the late 1960s the progress in truffle
cultivation seemed arrested despite the works of
Rebière and Mannozzi-Torini.
A breakthrough occurred in the early 1970s, when
researchers from the IPLA and the INRA developed
the inoculation of seedlings with Tuber in the nursery
(Chevalier, 2001). Almost 90 years before, Frank had
coined the term mycorrhiza and postulated that this
structure involved a symbiotic relationship (Trappe
et al., 2009). T. melanosporum-inoculated seedlings
were released to the market in France in 1973 (Cheva-
lier, 2001), greatly increasing plantation activity. On
the other hand, in Italy it gained momentum from 1982
(Bencivenga, 2001).
At that time French truffle growers had already
began to associate, and the government had established
public aids for plantation establishment (Olivier et al.,
1996). Italy organised the first International Truffle
Congress in 1968. Up to the 1980s the intensive culti-
vation techniques (Pallier method) were dominant in
plantations, whereas from the 1990s more extensive
models (Tanguy method) were proposed (Olivier et al.,
1996).
Spain only became involved in the international
truffle market in the 1960s, when wild truffières across
the country began to be systematically searched and
exploited. An alarming decrease in production was
observed from the 1980s, after 20-30 years of intensive
harvesting in a context of rural depopulation and in-
creasing forest stand density. Except for the Arotz esta-
te (around 600 ha planted in the 1970s), the plantation
of mycorrhizal seedlings was minimal until the 1990s.
In that decade truffle growers began to associate, and
regional governments established public assistance for
the establishment of plantations.
Current state in France, Italy
and Spain
The annual European production of T. melano-
sporum was an average of around 58 t for the period
2003-2012, although highly variable from year to year
(Table 1, Fig. 1).
In France, the production seems steady since the
1990s (Fig. 1), despite the rate of plantation (Table 1).
Our estimation of mean yield in mature plantations is
very low (Table 1), but it is consistent with the 0.5-3 kg
ha
–1
year
–1
cited by Escafre and Roussel (2006).
French growers benefit from a high domestic de-
mand (it consumes most of the French and Spanish
production), the support from public agencies to plan-
tation establishment (Sourzat, 2007), and an extensive
network of scientists and specialists (although much
of their work is not published in scientific journals)
(Table 1). The experience of experimental stations in
which researchers and growers closely collaborate,
such as that of Le Montat (Lot), seems especially in-
teresting.
In Italy, we estimate that the mean yield of mature
plantations is similar to that of France (Table 1). The
strengths of T. melanosporum cultivation are also
320 S. Reyna and S. García-Barreda / Forest Systems (2014) 23(2): 317-328
similar, with a greater emphasis on exportation
(Galluzzo, 2013). The introduction of exotic species
such as T. indicum s.l. and Tuber sinoaestivum Zhang
et Liu (Zhang et al., 2012) in Italian orchards may
become a serious problem (Murat et al., 2008; Zam-
bonelli et al., 2012).
In Spain, plantations have made up for the collapse
of wild production over the past few decades (Fig. 1).
The mean yield of mature plantations is somewhat
higher than in France and Italy (Table 1), despite the
fact that the mean age of plantations is lower (plan-
tation establishment started later). In the Arotz planta-
tion the yield in the late 1990s was lower than 2 kg ha
–1
year
–1
in non-irrigated areas, and up to 45 kg ha
–1
year
–1
in the irrigated areas (Carbajo, 1999).
Domestic consumption of truffles in Spain is less
than 10%, and promotion activities such as fairs are
still limited (Table 1). In some regions the high plan-
tation rates during the 2000s were mainly due to grants
covering 100% of the cost of plantation establishment
(excluding land purchase), thus making planting a
business in itself. Some experts argue that a part of
these plantations will not be carefully managed and
will be less likely to succeed.
Table 1. Main features of T. melanosporum production and associate activities in France, Italy and Spain
France Italy Spain
Mean production between seasons 2003-2004
and 2012-2013 (t year
–1
)
1
31.3 11.0 15.9
% truffles produced in plantations vs harvested
in the wild
2
90%-10% 50%-50% 60%-40%
Plantation surface (ha)
3
24,000 7,500 10,000
Recent rate of plantation (ha year
–1
)
3
800 400 1,000
Mean yield of mature plantations (kg ha
–1
year
–1
)
4
1.5 1.2 3.2
Main productive regions
2
Drôme (>6,500 ha), Marche (aprox. Teruel (>4,000 ha),
Lot, Vaucluse, 5,000 ha), Umbria, Soria, Huesca,
Dordogne, Gard Abruzzo Castelló
Hosts in plantations
5
Qh, Qi, Qr, Ca Qh, Qi, Oc, Ca Qi, Ca, Qf, Qc
No of nurseries
6
27 8 27
Price of seedlings (euros)
6
5-19 8-14 4-8
No of growers/harvesters
7
20,000 180,000
7
10,000
No of growers/harvesters associations
7
36 50 20
No of truffle fairs and retail markets
8
129 68 in Umbria, 15
Piemont, Toscana
and Abruzzo
No of research articles (and No of citations) on
truffles (2008-2012)
9
13 (179) 43 (209) 32 (118)
1
According to the European Group for Truffles, Oliach (pers. comm.) and Gregori (pers. comm.).
2
According to Gregori (2007) and Sourzat (2007).
3
Estimated from Escafre and Roussel (2006) and Gregori (2007).
4
We estimated the mean yield of mature plantations (1) taking into account the proportion of wild production, (2) assuming that
young plantations (less than seven years old) do not have a quantitatively meaningful production, and (3) estimating the surface of
young plantations from the recent plantation rate.
5
Qh: Quercus humilis Mill. (= Q. pubescens), Qi: Quercus ilex L, Qr: Quercus robur L, Ca: Corylus avellana L, Oc: Ostrya
carpinifolia Scop., Qf: Quercus faginea Lam., Qc: Quercus coccifera L.
6
According to Cocina et al. (2013).
7
According to GET (2002). Pettenella et al. (2004) estimated that only 5% of the Italian harvesters are professionals.
8
Including events dedicated to any Tuber species. According to Cena (2000), Materozzi (2005), FFT (2011), Marone (2011) and
FFT (2012).
9
According to Web of Science. Only articles in which the first author works in a research centre of the country are considered.
Articles on all species of Tuber are considered.
Cultivation outside the native range
North America
The first T. melanosporum-inoculated plantations
were established in 1979 in North Carolina and 1980
in California, and the first sporocarps were harvested
in 1987 in northern California (Renowden, 2005; Le-
fevre, 2012). Nowadays there are plantations from
California to southern British Columbia (Canada) and
from central Texas to North Carolina (Renowden,
2005; Lefevre, 2012). Most of them were planted after
2003 (Pilz et al., 2009). Sporocarp production has been
reported in California, North Carolina, Tennessee,
Texas, Oregon and British Columbia (Lefevre, 2012;
Berch, 2013). Soils are usually limed to raise the pH.
C. avellana, Q. robur and Q. ilex are commonly used
as host plants.
These plantations have usually spread without any
coordinated initiative or technical assessment. Further-
more, in some cases the sites are far from the climatic
requirements of T. melanosporum (Lefevre, 2012). The
overall yields are far from optimum (Table 2).
Australia and New Zealand
New Zealand was the first country in the Southern
Hemisphere to establish T. melanosporum plantations
(in 1987) and to harvest sporocarps (in 1993). The ini-
tiative was led by a scientist (Ian Hall), supported by
the government (Hall and Haslam, 2012). Its develop-
ment was based on climatic and edaphic studies, pro-
duction of mycorrhizal seedlings in the country and
quality control of mycorrhizal seedlings. A variety of
field essays were established to determine the best
management practices (Guerin-Laguette et al., 2009).
However, most information remains unpublished
due to confidentiality (Hall and Haslam, 2012). C.
avellana and Q. robur were initially used as host plants,
and Q. ilex was introduced later (Zambonelli et al.,
2009).
Australia began to plant some years later and
benefited from New Zealand experience, important
subsidies for plantation establishment and a more
continued government support for research (Hall and
Haslam, 2012), thus being reflected in the planted
surface (Table 2). Plantations are currently common
in Western Australia (notably around Manjimup and
Pemberton), Tasmania, New South Wales and Victoria
(Lee, 2008). The agricultural practices have been
adapted to the environmental conditions: they are more
intensive than in Europe and plantation densities are
higher (Zambonelli et al., 2009).
The productive results in both countries are con-
trasting (Fig. 2): we estimate that the mean yield of
mature plantations is 0.5 kg ha
–1
year
–1
for New Zea-
land and 9.2 kg ha
–1
year
–1
for Australia. The latter can
Black truffle cultivation: a global reality 321
Figure 1. Estimates for T. melanosporum production from season 1990-1991 in France, Italy, Spain (according to the European
Group for Truffles for the data up to 2009-2010, and to Oliach, pers. comm. and Gregori pers. comm. for the recent ones) and
Australia (Duell, 2012).
be considered an important success, although the
differences in productivity among plots are high and
most production comes from a limited number of
plantations (Hall and Haslam, 2012).
One important advantage for these countries is that
forests are dominated by endomycorrhizal plants or
ectomycorrhizal fungi very different from the Euro-
pean ones (Zambonelli et al., 2009). As calcareous
soils are scarce, liming the soil is a common practice,
like in North America, and rising of the pH can also
reduce the competitiveness of the scarce ectomy-
corrhizal fungi (Lefevre and Hall, 2000). Australia and
New Zealand produce in counter-season to the main
producers and consumers, and this helps their exports
given that the truffles are mostly consumed fresh. In
addition, their domestic demand is rapidly increasing:
truffle fairs are organised to spread its culinary use,
and about 800 kg were consumed in Australia in 2012
(Duell, 2012), with the bulk exported.
The success of some plantations is threatened by the
accidental introduction of T. brumale (through the
imported sporocarps used as inoculum) in both countries
(Linde and Selmes, 2012; Guerin-Laguette et al., 2013).
China
The first T. indicum s.l. plantation was established
in Taiwan in 1989, and the first sporocarps were har-
vested in 1997 (Hu et al., 2005). In continental China,
the first T. indicum s.l. sporocarps and the first T. me -
lanosporum sporocarps were harvested in neigh-
bouring plantations in Guizhou (Wang, 2012). Another
T. melanosporum plantation was established in Hunan
(Wang, 2012), despite the excessive summer tempe-
ratures and low winter temperatures (Hall, 2013). More
T. indicum s.l. plantations have been established in
recent years in Guizhou, Hunan, Sichuan and Yunnan
using native Quercus, Pinus and Castanea as hosts
(Wang, 2012).
In most cases these activities were supported by uni-
versities and implied the development of nursery tech-
niques. However, quality control of seedlings is not
common and many plantations are established on forest
soils (Wang, 2012). Most truffles are exported and the
domestic demand is low.
Europe and the Mediterranean basin
T. melanosporum cultivation is being essayed across
Europe and the Mediterranean basin. However, these
322 S. Reyna and S. García-Barreda / Forest Systems (2014) 23(2): 317-328
Table 2. Main features of T. melanosporum plantations outside its natural distribution area
USA New Zealand Australia Chile South Africa Argentina
Date of first plantation 1979 1987 1993,500 2003 2008 2010
Production (kg year
–1
)
1
40 <50 4,500 7 0 0
Plantation surface (ha)
2
120 100 700,500 200 30 40
Recent rate of plantation (ha year
–1
)
3
20 Very low 30,500 35 10 20
No of nurseries
4
446,500 422
Price of seedlings (euros)
4
11-19 28-33 15-46 10-15 11 12
1
According to Lefevre (2010), Duell (2012), Guerin-Laguette et al. (2013) and Henríquez (pers. comm.)
2
According to Pilz et al. (2009), Zambonelli et al. (2009), Hall and Haslam (2012), Henríquez (pers. comm.) and Miros (pers.
comm.)
3
According to Treloar (2013); to the comparison of current surfaces to those 5-7 years ago (Ramírez et al. 2007; Lee 2008); and
in the case of the USA to seedling production of the most important nurseries (Cocina et al. 2013) and common plantation densities.
4
According to Cocina et al. (2013).
Figure 2. Estimation of current production of T. melanosporum.
plantations are still young and sparse, and in many
cases the sites do not fulfil T. melanosporum climatic
requirements. Some plantations have already produced
sporocarps in Israel, Morocco and Sweden (Khabar
2007; Turgeman et al., 2012; Wedén et al., 2013).
The interest on T. aestivum/T. uncinatum cultivation
is also recent and widespread. These plantations are more
likely to succeed given the wider ecological requirements
of this species (Stobbe et al., 2013). Israel is an
illustrating example (Turgeman et al., 2012). In 1994 T.
melanosporum-inoculated seedlings were planted, and
in 1999 a sporocarp was harvested. But in 2002 it was
impossible to find T. melanosporum mycorrhizas in the
plantation. In 1999 more seedlings were planted, but T.
aestivum-inoculated seedlings were non-intentionally
introduced. In 2010 about 15 kg ha
–1
of T. aestivum were
harvested and it has continued to fruit.
South America and South Africa
Following New Zealand’s example, the Universidad
Católica del Maule started a project to cultivate T.
melanosporum in Chile with government support (Fun-
dación para la Innovación Agraria). The first plantation
was established in 2003 and the first truffles were
harvested in 2009 (Table 2). Most plantations are
located between the regions of Valparaíso and Los
Ríos. Soils are usually limed to raise pH. Q. robur, Q.
ilex and C. avellana are the most used host plants (Hen-
ríquez, pers. comm., www.trufaschile.cl).
The initiative was based on a climatic and edaphic
study of Chile, and the development of nursery techni-
ques to produce mycorrhizal seedlings. More recently,
the public initiative is addressed to establish field es-
says aimed at determining the best management prac-
tices and the environmental factors that enhance fruit-
ing. Public efforts have been also launched to promote
the association of growers, to train farmers and to
develop commercial strategies. Being in the Southern
Hemisphere, Chile has the opportunity to produce
counter-season to Europe. In contrast, their domestic
demand is still very low, and their farmers need tech-
nical assessment on quality of mycorrhizal seedlings
and management practices.
In 2008 a nursery was established in Argentina and
the first seedlings were planted in 2010 (Table 2). The
first plantations are located in south Buenos Aires
region and Río Negro (Henríquez, pers. comm.). Peo-
ple in neighbouring countries like Uruguay, Peru and
Brazil have recently shown interest in starting truffle
cultivation projects (Henríquez, pers. comm.).
In South Africa, T. melanosporum plantations were
initiated in 2008 through a joint venture and the
establishment of several nurseries (Table 2). Q. robur,
C. avellana and Q. ilex are the most used host plants
(Miros, pers. comm., http://woodfordtruffles.co.za/).
Basic research
The cultivation of T. melanosporum is not comple-
tely domesticated, as the uncertainties around the
mating process remain (Selosse et al., 2013). Basic
research on truffles has been constricted by the dif-
ficulties to observe their development: the symbiotic
phase is microscopic and the growth of the mycelium
in pure culture is slow, whereas the sporocarp grows
underground and over a period of several months.
In recent years molecular techniques are allowing a
great progress: they are used to identify sporocarps,
mycorrhizas and mycelia; to recognise genetically
identical individuals (genets); and to determine the
molecular bases of truffle biology. The genome of T.
melanosporum has been recently sequenced by the
Tuber Genome Consortium, opening the possibilities
of genomics to truffle research (Martin et al., 2010).
These tools support novel approaches to important
research gaps in the mechanisms regulating symbiosis,
the trophic state of the fungus, population genetics and
the mechanisms involved in fruiting. Linking gene
functions and interactions with the biology and ecology
of the fungus will improve the design and management
of plantations.
An important breakthrough has been the confirma-
tion that T. melanosporum is heterothallic (Riccioni
et al., 2008), the identification of two mating types,
and the characterisation of the genes involved (Rubini
et al., 2011a). However, the sex organs are still largely
unknown: only ascogonia have been rarely reported
(Callot, 1999). Le Tacon et al. (2013) hypothesised
that the ascogonium connects the mycorrhiza to the
sporocarp during all its development.
The understanding of the ectomycorrhizal relation
is being improved by recent studies on the signalling
pathways to its establishment, the mechanisms of the
fungus to inhibit the defensive response of the plant,
the mechanisms of the partners to control each other,
the role of nutrients transfer in the maintenance of the
relation, the ability of the fungus to cleave sucrose
Black truffle cultivation: a global reality 323
(Plett and Martin, 2011) or the role of truffle volatiles
in the first contact (Splivallo et al., 2011).
Although T. melanosporum retains some genes en-
coding enzymes responsible for degrading plant living
cells, it has less degradative enzymes than saprotrophic
fungi, thus indicating a lower ability to degrade organic
tissues (Plett and Martin, 2011). This makes the fungus
highly dependent on its host: Le Tacon et al. (2013) found
that even in the late stages of the sporocarp development
most carbon was supplied by the plant. The analysis of
the transcription factors can help to understand the
variations in the trophic behaviour of the fungus in each
developmental stage (Montanini et al., 2011).
The methods for quantifying mycelium of T. mela-
nosporum in the soil have allowed Liu et al. (2014) to
monitor its spread and increase of density in young
plantations. Suz et al. (2008) showed the relation bet-
ween the abundance of mycelium and the formation of
the brûlé. Liu et al. (2014) also hypothesised the
existence of a mycelium-carrying capacity of the soil,
and it would be interesting to understand the relation
of this with the abundance of volatiles.
Murat et al. (2013) found that T. melanosporum
genets in young plantations were mostly small (dia-
meter lower than 1 m), and few of them were found
from year to year. Rubini et al. (2011b) showed that in
the nursery genets compete each other for root tips,
leading to the exclusion of most genets in 18 month-
old seedlings. In the field intraspecific competition
causes a spatial separation between mating types that
can affect fruiting potential (Rubini et al., 2011b).
Selosse et al. (2013) hypothesised that the mating-type
genes could also be controlling vegetative incompa-
tibility, but Iotti et al. (2012) did not find genes related
to mating-type heterokaryon incompatibility in T.
melanosporum.
The understanding of the mechanisms triggering
fruiting is being improved by the studies on the re-
gulome involved in developmental shifts from the sym-
biotic to the reproductive phase, on carbon transfer
from the plant to the sporocarp, and on mating types.
But it is also essential to know which factors of the soil
environment are involved: Pacioni et al. (2014) sug-
gested that variations in soil temperature and water
content in spring are key, and proposed to use ground
penetrating radars to monitor the sporocarps without
disturbing their environment.
The translation of basic research to agricultural
practices can be obscured by the interaction between
T. melanosporum and other soil organisms (e.g. fungal
competitors, bacteria modulating the mycorrhizal
relation, or interacting with the fruiting). Metageno-
mics makes the study of soil microbial communities
easier.
Cultivation challenges
Nowadays many of the practices in T. melanosporum
cultivation are still empirical. The success of planta-
tions cannot be guaranteed: plantations largely differ
in the sporocarp yield, the percentage of productive
trees and the age at which they start producing (pro-
ductive onsets at age 4 and later than year 15 have been
reported).
The quality of some nursery seedlings is a problem
in countries without mandatory certification systems.
It can be the cause of failure for some plantations and
the way that exotic species are introduced. The pro-
duction of seedlings with known mating types is a
challenge for the future, since they are currently ino-
culated with spores (Rubini et al., 2011b).
The experience in North America and the Southern
Hemisphere proved that it is possible to grow truffles
in naturally acidic soils after liming. But if not enough
lime is added to stabilise the pH, it decreases in a few
years, making periodic liming necessary.
Sourzat (2008, 2010) drew attention to other soil-
related issues jeopardising the success of plantations
in France: the chemicals applied in the previous land
use and the high pressure of ectomycorrhizal compe-
titors (particularly T. brumale and T. aestivum) in land-
scapes dominated by forest patches. The competition
of soil-borne fungi points to the need to understand
better the factors determining the structure of ecto-
mycorrhizal communities and their dynamics, in-
cluding the possible role of truffle volatiles (Splivallo
et al., 2011).
In contrast, in Spain the plantations are usually
located in extensive agricultural landscapes, so these
problems are less frequent. However, temperatures are
higher and rainfall is more scarce and irregular. This
reduces the survival of the sporocarps during the sum-
mer, making research on irrigation and soil water con-
servation a priority.
Other challenges in French plantations (Sourzat,
2008, 2010) are the short productive life of some young
plantations and the high stand densities in mature plan-
tations. The latter draws attention to the importance of
pruning and thinning. Old plantations (planted before
324 S. Reyna and S. García-Barreda / Forest Systems (2014) 23(2): 317-328
the 1970s) which are not producing currently are seen
as an opportunity for spreading truffle production by
forest management.
Large concentrations of plantations pose new
threats: e.g. the truffle growers in Sarrión (Teruel)
complain that in recent years the damages of insects
on sporocarps are increasing, especially in dry and hot
autumns.
Outside France and Italy most plantations are still
young and management techniques are not adapted to
the local conditions (soil water and temperature regi-
mes, aeration, organic matter, host plants, soil-borne
ectomycorrhizal community, etc.) yet. There is not a
unique management system that works in all the envi-
ronmental conditions suitable for T. melanosporum
growth. Monitoring mycorrhizas and mycelium, tree
growth and physiology, and soil microclimate in these
plantations is highly recommendable. In this way, it
could be assured that they remain potentially success-
ful, and that management practices could be quickly
improved.
A major problem in Australia is the abundance of
sporocarps growing near the soil surface in irrigated
plantations. These are more frequently damaged by
pests, diseases, desiccation and frosts. The first studies
on the matter point that reducing the irrigation and
increasing the irrigation interval could help to decrease
the damages (Eslick and Dell, 2013).
In countries with a meaningful wild production
(Spain and Italy) the conservation of this production
is an important concern: this involves sustainable har-
vesting and habitat improvement (Garcia-Barreda and
Reyna, 2013).
Finally, if climate change predictions for the Medi-
terranean basin (decrease in summer rainfall, increase
of temperatures and increase in interannual variability
of both rainfall and temperature) are confirmed, the
suitability of many native T. melanosporum areas for
cultivation (specially the warmest ones) will be redu-
ced (Colinas et al., 2007). A planning effort will be
needed to assess the future suitability of the current
native range and to adapt the cultural practices to the
new situation.
Acknowledgements
This work was partially funded by the INIA project
PET 2007-13-C07-04. We would like to thank Luz
Cocina for her help with the text in English.
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