Trifling variation in truffles

Of the ten species of European truffle (fungi of the genus Tuber, phylum Ascomycota), some have economic value because of their organoleptic properties (taste and perfume), in particular the black truffle (Tuber melanosporum Vitt.) and the summer and burgundy truffles1,2. The black truffle is mainly found in Spain, France and Italy (Fig. 1a), and it shows variation in several traits, including in its famous organoleptic properties, across this geographical range. Here we show that this variation probably results from environmental, rather than genetic, influences. Figure 1 Geographic and genetic characteristics of the black truffle Tuber melanosporum Vitt. a, The western European geographical range (shaded area) of Tuber melanosporum and sampling localities (stars); numbers refer to samples shown in b. All truffles (n =208) were collected in natural habitats, except one sample which was collected in an artificial ‘truffle-field’. b, Example of RAPD patterns obtained with the OPF-14 primer (Operon Technologies, Alameda) for truffles from four locations (numbers refer to a); arrows indicate polymorphic bands used. Sizes on left are in kilobase pairs. c, Analysis of isolation by distance according to ref. 7, using six RAPD loci (generated by primers OPF-11, OPF-13, OPF-14 and OPB-2) and the only two polymorphic microsatellite loci out of the nine assessed, (GAGT)14and (GTTA)9, showing two alleles each. Computations were performed with Genepop version 3.1b (ref. 8). The increase in genetic differentiation with geographic distance was not significant (Mantel test, 105 permutations, P