MYCORRHIZA BASICS
Truffles are the edible fruiting bodies of a subterranean fungus known as a Mycorrhiza, which means “root fungus”. Mycorrhizae form a symbiotic relationship with a host tree because they cannot synthesize sugars and other carbohydrates on their own. The tree provides the truffle with a source of carbohydrates and nutrients, and in return the fine thread-like filaments (mycelia) of the truffle, coats the tips of the tree roots to form mycorrhiza which helps the tree to absorb soil minerals and nutrients.
In affect the mycorrhiza is able to increase the effectiveness of the trees roots and provide phosphorus and trace elements that would normally be unavailable to the tree.
CULINARY USES
Truffles have a rather pungent aroma of ‘fresh earth’ and sweet mushrooms. Their taste can permeate and enhance many foods such as soups, dips and patès, salads, sauces and dressings, omelettes and main meals. The mystique and gourmet experience associated with their unique aroma, flavour and taste accounts for their demand by consumers and high market value.
TRUFFLE VARIETIES
There are many types of truffles. The main truffle types are:
• French Black or Périgord truffle (Tuber melanosporum) named after the Périgord region of France
• The white truffles (Tuber magnatum from the Piedmont region of Italy and Tuber borchii from Tuscan)
• The Chinese truffle (Tuber sinense, Tuber indicum and Tuber himalayense) from Asia.
• The Burgundy or summer truffle (Tuber unicinatum / aestivum) from Central Europe, Turkey and North Africa.
Truffles vary in size and shape. They typically range in size from that of a small nut to the size of a tennis ball and appear rounded with a knobbly surface.
HOST TREES
The famous highly prized French Black Truffle is botanically named Tuber melanosporum and lives on several host species of Oaks and Hazel trees. The most commonly used species are as follows:
Botanical name |
Common name |
Description |
| Quercus robur |
English Oak |
Deciduous tree growing to about 20 metres. However, in a Truffière their height is much reduced by competition and pruning |
| Quercus ilex |
Holm Oak or Holly Oak |
Evergreen tree growing to about 15 metres |
| Quercus suber |
Cork Oak |
Evergreen tree growing to about 15 metres |
| Corylus avellana |
Hazel (Hazelnut) |
Deciduous small tree branching from base growing to about 6 metres |
LIFE CYCLE
The truffle fungus infects the new root growth in spring and the developing mycelia spread out in the soil. From about January it is believed the tiny truffle sporophytes begin to develop (through a sexual process) and grow to maturity in the June, July and August period. Obviously there are specialised growing conditions (temperature, soil moisture, pH and nutrition) that need to be maintained to optimize the likelihood of truffle development.
It should be noted that the exact environmental triggers that affect truffle initiation and development and the process are not clearly understood. This is still the subject of much on going research and development.
Growers have reported harvesting Truffles at four years but more commonly production starts at around seven years after planting and then increases each year. Of course Oak trees are very long lived so truffles can continue to be harvested over many decades.
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| Oak root tip infected with Tuber melanosporum |
English Oak (Quercus robur ) |
Holm Oak (Quercus ilex) |
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