The cultivation of mycorrhizal mushrooms - still the next frontier!

Edible mushrooms fall into three broad groups: the saprobes which grow on animal wastes and/or dead plant material, the pathogenic species that grow on living plants or animals, and the mycorrhizal species that grow in an intimate association with the roots of suitable host plants. While the vast majority of the world’s mushroom market is filled by the saprobic mushrooms, the aromas and flavours of the mycorrhizal species remain unrivalled – and often have prices to match. The first cultivation of a mycorrhizal mushroom dates back to the early 19th Century when Pierre Mauléon and later Joseph Talon in France stumbled upon a method for Tuber melanosporum (Périgord black truffle). They found that by transplanting seedlings from under a Périgord black truffle producing tree into a new area, eventually they also produced truffles. This method remained the mainstay of the truffle industry in Europe until the early 1970s when a new method of producing truffle mycorrhized plants was devised using spores as the inoculum. Subsequently spore inoculation techniques were also found to work with Rhizopogon rubescens (shoro). However, this method has not been a success with any of the aboveground edible mycorrhizal mushrooms. For a handful of the aboveground mycorrhizal mushrooms, inoculating with cultures have proven the only effective way of producing mycorrhized trees in nurseries and fruiting bodies in plantations, for example, Lactarius deliciosus (saffron milk cap). The production of mushrooms of the mycorrhizal species Lyophyllum shimeji (honshimeji) in pure culture must be regarded as an anomaly as these methods have not been successful for any other species of edible mycorrhizal mushroom. The vast majority of the 1000 plus species of mycorrhizal mushrooms remain uncultivated and progress has been anything but spectacular. It is not possible to summarise in this short paper the 1000 pages in Taming the Truffle (Hall et al. 2007, 2009) and the new book on edible mycorrhizal mushrooms by Zambonelli and Bonito (2012) and instead briefly outlines the current state of our knowledge, the problems we now face, some reasons for failures, and suggests a vision for the future.