Improving the production of truffles

Abstract

Truffles, those delectable fungi used by chefs for flavoring, are hard to find. Truffles (genus Tuber) grow as ectomycorrhizae on roots of trees and shrubs, and are hunted in forest areas using pigs or trained dogs. Demand easily exceeds supply because only ∼20 tons are produced worldwide, and prices can reach US$3000 per kg for white truffles. In recent years, large plantations have been established in southern European countries, New Zealand, Australia and the USA, but close attention is needed to minimize the level of contaminating and competing ectomycorrhizal fungi on the root systems of inoculated plants. However, morphological distinctions are often narrow and rigorous identification impossible. The availability of reliable methodology for identification of contaminants is becoming increasingly important because buyers demand that plantlets from truffle orchards infected with prized species of truffles be certified.Improvements in molecular techniques have now opened up the possibility of using molecular tools to augment or replace traditional morphology. While working to verify the formation of ectomycorrhiza in Tuber-infected seedlings of oak (Quercus pubescens), Antonella Amicucci and colleagues1xMorphological and molecular characterization of Pulvinula constellatio ectomycorrhizae. Amicucci, A et al. FEMS Microbiol. Lett. 2001; 194: 121–125CrossRef | PubMedSee all References1 discovered that the ascomycete, Pulvinula constellatio, formed competing ectomycorrhizal relationships. The authors described the fungus morphologically and adapted a PCR approach for establishing the identity of P. constellatio by developing a restriction-fragment-length polymorphism method, based on the internal transcribed sequence of the ribosomal RNA gene. They showed that the molecular procedure provided a reliable method for showing the presence of P. constellatio.P. constellatio now joins a list of other discomycetes such as Pulvinula globifera and Sphaerosporella brunnea that also compete with Tuber spp. on cultivated seedlings of oak. S. brunnea, in particular, forms mycorrhizae that are morphologically similar to those of the prized white and black species of truffles, Tuber magnatum and Tuber melanosporum, respectively, and thus are difficult to distinguish. The adaptation of molecular probes promises to provide efficient tools that can be used to certify the purity of plants inoculated with edible species of Tuber, thereby helping to increase the availability of uncontaminated truffle-infected plantlets used in artificial truffle cultivation. For those who love good food, this couldn't be better news.