POPULATION STRUCTURE ANALYSES OF TUBER BORCHII: THE ITALIAN BIANCHETTO TRUFFLE

Objectives: Tuber borchii (Ascomycota, order Pezizales) is an excellent truffle with a significant local market in Italy. Despite the great use of this truffle in scientific experiments, knowledge on its intraspecific variability is scarce. The objective of this work was to investigate the evolutionary forces shaping genetic variability in this ascomycetes with a classical phylogenetic approach and a stochastic models (Kingman, 2000) to study the gene flow, migration and mutation rate. Material and Methods : To handle these goals, analyses were carried out using 61 samples from 11 different Provinces of Italy trying to have, as far as possible, an heterogeneity in growing conditions, habitats and hosts. Samples were identified considering anatomo-morphological characters (Zambonelli et al,. 2000). On the other side, DNA was extracted and four loci markers (ITS, IGS, β-tubulin and PKC) were screened to look for polymorphisms. Phylogenetic analyses of the sequence data were performed with maximum parsimony and maximum likelihood with PAUP (Swofford, 2003) and data were combined with MrBAYES software (Huelsenbeck and Ronquist, 2001) to have more realistic information. Approximation of the evolutionary history of populations was facilitated by use of the SNAP Workbench (Price and Carbone, 2005). Results : Genetic data showed the presence of two different haplotypes named 1 and 2, which were difficultly resolved by morphological analyses. The haplotypes are descended from a common ancestral population at some time in the past and have since diverged with a very low level of gene flow with a weak asymmetrical migration from haplotype 1 to haplotype 2. Moreover the oldest mutations are found in the haplotype 2. Conclusion : These results may allow us to formulate an early hypothesis on the natural processes of evolution of Italian T. borchii populations, in fact the two major phylogenetic groups observed may represent a species partition where haplotype 1 and 2, could be in the beginning of a speciation event or represent cryptic species