the period from 1990 to 2005 Mexico annually loosed an average of 318,000 ha of
forest. This represents one of the highest deforestation rates in the world, surpassed
for example from 1990 to 2010 only by Brazil, Indonesia, Sudan, Myanmar,
Nigeria, and Tanzania (GFR 2010). As a result, Mexico currently has serious
environmental problems in terms of soil erosion and additionally the country is an
important emitter of greenhouse gases, ranking 13th worldwide (Myers-Madeira
2008). Reforestation is a complex issue, which includes among other technical
limitations in the country, a low survival rate when trees are planted under field
conditions. This is particularly dramatic for some forest species like pines (Pinus
spp.), where the survival transplanting rate ranges from 0 to 20 % in Mexico. One
reason which explains this low survival is the lack of ectomycorrhizal symbionts in
the roots of most of the forest species produced in greenhouses, whose presence is
obligate when they grow under natural conditions. However, inoculation of trees
with EEMs has not been traditionally included in plant production in most of the
countries. Therefore, the biotechnological development of inoculation of forest
trees with ectomycorrhizal fungi is an urgent need in countries like Mexico. A
criterion for selection of EEM that has recently gained importance is their edibility
(Aggangan et al. 2013), due to their enormous social, economic, and environmental importance. In Mexico for example, more than 400 species of wild edible
mushrooms are consumed, and the country is one of the most important cultural
and genetic centers of diversity of edible mushrooms worldwide (Pérez-Moreno
et al. 2010). Traditionally, organic layers, which include mainly fermentation
horizons, A and O soil horizons are used as a source of ectomycorrhizal propagules
to inoculate forest trees. However, this methodology has different disadvantages,
which include (i) use of great quantities of forest organic material with the subsequent negative environmental and economic impact; (ii) inconsistency in the
quality control of the inoculum due to the heterogeneity of distribution of ectomycorrhizal sources of inoculum in natural conditions; and (iii) probability of
introduction of propagules of pathogens or weeds in the areas of tree production
with their associated risks (Pérez-Moreno 2002). Taking into account this scenario,
in the Colegio de Postgraduados, Texcoco, Mexico different efforts have been
developed during the last two decades, led by the author of this chapter, in order to
develop a biotechnology of inoculation of native trees, mainly in the genera Pinus,
Quercus, and Abies, with EEMs.
Till date, some successful results have been generated by inoculating forest trees
either with ectomycorrhizal mycelium or spores. Inoculation of strains of the
ectomycorrhizal genera Hebeloma, Suillus, and Pisolithus, have shown to be
beneficial on tree growth (García-Rodríguez et al. 2006; Pérez-Moreno et al. 2010).
However a much cheaper, simpler, and efficient technology has been developed by
using ground pilea of the sporomes containing enormous amounts of ectomycorrhizal spores. Conspicuous root colonization, reaching up to 97 %, has been successfully developed by inoculating ground pilea mainly with different fungal
species (Fig. 6.10) included in the edible ectomycorrhizal genera Laccaria, Hebeloma and Suillus (Carrasco-Hernández et al. 2010; Méndez-Neri et al. 2011;
Martínez-Reyes et al. 2012). All of the studied species are widely marketed in
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J. Pérez-Moreno and M. Martínez-Reyes
forest. This represents one of the highest deforestation rates in the world, surpassed
for example from 1990 to 2010 only by Brazil, Indonesia, Sudan, Myanmar,
Nigeria, and Tanzania (GFR 2010). As a result, Mexico currently has serious
environmental problems in terms of soil erosion and additionally the country is an
important emitter of greenhouse gases, ranking 13th worldwide (Myers-Madeira
2008). Reforestation is a complex issue, which includes among other technical
limitations in the country, a low survival rate when trees are planted under field
conditions. This is particularly dramatic for some forest species like pines (Pinus
spp.), where the survival transplanting rate ranges from 0 to 20 % in Mexico. One
reason which explains this low survival is the lack of ectomycorrhizal symbionts in
the roots of most of the forest species produced in greenhouses, whose presence is
obligate when they grow under natural conditions. However, inoculation of trees
with EEMs has not been traditionally included in plant production in most of the
countries. Therefore, the biotechnological development of inoculation of forest
trees with ectomycorrhizal fungi is an urgent need in countries like Mexico. A
criterion for selection of EEM that has recently gained importance is their edibility
(Aggangan et al. 2013), due to their enormous social, economic, and environmental importance. In Mexico for example, more than 400 species of wild edible
mushrooms are consumed, and the country is one of the most important cultural
and genetic centers of diversity of edible mushrooms worldwide (Pérez-Moreno
et al. 2010). Traditionally, organic layers, which include mainly fermentation
horizons, A and O soil horizons are used as a source of ectomycorrhizal propagules
to inoculate forest trees. However, this methodology has different disadvantages,
which include (i) use of great quantities of forest organic material with the subsequent negative environmental and economic impact; (ii) inconsistency in the
quality control of the inoculum due to the heterogeneity of distribution of ectomycorrhizal sources of inoculum in natural conditions; and (iii) probability of
introduction of propagules of pathogens or weeds in the areas of tree production
with their associated risks (Pérez-Moreno 2002). Taking into account this scenario,
in the Colegio de Postgraduados, Texcoco, Mexico different efforts have been
developed during the last two decades, led by the author of this chapter, in order to
develop a biotechnology of inoculation of native trees, mainly in the genera Pinus,
Quercus, and Abies, with EEMs.
Till date, some successful results have been generated by inoculating forest trees
either with ectomycorrhizal mycelium or spores. Inoculation of strains of the
ectomycorrhizal genera Hebeloma, Suillus, and Pisolithus, have shown to be
beneficial on tree growth (García-Rodríguez et al. 2006; Pérez-Moreno et al. 2010).
However a much cheaper, simpler, and efficient technology has been developed by
using ground pilea of the sporomes containing enormous amounts of ectomycorrhizal spores. Conspicuous root colonization, reaching up to 97 %, has been successfully developed by inoculating ground pilea mainly with different fungal
species (Fig. 6.10) included in the edible ectomycorrhizal genera Laccaria, Hebeloma and Suillus (Carrasco-Hernández et al. 2010; Méndez-Neri et al. 2011;
Martínez-Reyes et al. 2012). All of the studied species are widely marketed in
208
J. Pérez-Moreno and M. Martínez-Reyes