Ploidy and chromosomal number in Tuber aestivum

Chromosome number is generally considered to be the most accurate and direct measure of ploidy. In fungi, however, counting of chromosomes is difficult and inaccurate because of their small size. To date truffles have been characterized using molecular approaches (analysis of DNA and PCR-based techniques) in order to find out differences among species, but not by a cytogenetical approach. Although the small size of truffle chromosomes is of some hindrance for a cytogenetic study, in the present work Tuber aestivum chromosome counts were determined in metaphase configurations from haploid nuclei of ascospores by aceto-orcein staining. Nuclear chromosome number and topography were also evaluated by propidium iodide DNA staining using confocal microscopy. Tuber aestivum was found to possess a basic number of 5 or 6 chromosomes, medium length ≤0.95 μm. The karyology of ascospores during their developmental stages was also investigated.