Species recognition in the truffle genus Tuber -- the synonyms Tuber aestivum and Tuber uncinatum

The two morphologically similar truffles Tuber aestivum and T. uncinatum have caused confusion because T. uncinatum is regarded by different authors, as either a distinct species, variety, subspecies, or synonym of T. aestivum. A clarification of the relationship between the two truffles would help both conservation biology and cultivation. We aimed both to test the reliability of the only quantitative morphological character used to distinguish the two taxa, i.e. the height of the spore reticulum, and to compare sequences of the ribosomal DNA (rDNA) internal transcribed spacer (ITS) region. Our study included 117 fruit bodies of T. aestivum and T. uncinatum, originating from eight European countries. The results showed that the spore reticulum height is not diagnostic. The phylogenetic analysis of ITS sequences from 81 fruit bodies and an additional 32 sequences from GenBank showed that T. aestivum and T. uncinatum were intermingled in one highly supported (100% bootstrap) monophyletic clade, separate from its sister species Tuber mesentericum. We conclude that T. aestivum and T. uncinatum are synonyms and the species should be named T. aestivum, as the oldest name has priority. For traders, T. aestivum syn. T. uncinatum should be used until conformity has been reached.