Ectomycorrhizal fungi live in a symbiotic (mutually beneficial) relationship with the roots of certain living trees. Unlike other commercially cultivated fungi, they cannot be grown on dead materials. There are a number of edible species, including porcini (Boletus edulis), matsutake (Tricholoma matsutake) and truffles (Tuber species). These are all native to the northern hemisphere, where they are only available fresh during short growing seasons in the autumn and winter.
Truffles – the most expensive foods in the world – are the reproductive structures of Tuber species. They are produced underground and emit a distinctive smell when ripe with spores. Périgord black truffles (Tuber melanosporum) are considered delicacies for their distinctive earthy, musky flavour, which is imparted to food by even a tiny sliver.
Truffles in New Zealand
Since the mid-1980s, truffles have been the focus of a small group of New Zealand researchers and growers. The first truffles grown in the southern hemisphere resulted from experimental work by Ian Hall of Crop & Food Research. Using techniques developed by French and Italian scientists, he infected oak and hazel tree seedlings with Périgord truffle mycelia. In 1987 and 1988 they were planted in a number of places around New Zealand, and in 1993 a few small truffles were harvested near Gisborne.
By 2007 New Zealand had over 100 truffières (truffle plantations), ranging in size from a few dozen to many thousands of trees. Nine plantations had produced truffles, and at least one harvested more than 40 kilograms of truffles per hectare annually. The domestic market accounted for the entire crop, which was worth around $3,500 per kilogram.
Other truffles – the bianchetto (T. borchi) and the burgundy (T. uncinatum) – have been grown successfully in New Zealand. Although not as highly regarded as Périgord truffles, they still sell for a good price.
There is potential to increase New Zealand’s export trade of fresh mushrooms to Asian markets if productivity can be raised. New Zealand’s extensive areas of managed pine forests could support crops of edible ectomycorrhizal fungi. To this end, scientists are investigating whether they can cultivate shoro (Rhizopogon rubescens) and matsutake (Tricholoma matsutake). A few other ectomycorrhizal fungi are promising candidates for cultivation, but New Zealand has strict import restrictions on many edible fungi species.