Persistence of Tuber melanosporum in truffle orchards in North Carolina, USA.

A survey was conducted to determine the persistence of mycorrhization by Tuber melanosporum in truffle orchards established with European and American species of oak and common hazel trees in North Carolina. The trees had reportedly been inoculated and colonized by T. melanosporum prior to planting. Root samples were collected from 95 trees among seven orchards in 2015 and roots were analyzed by morphology and quantitative PCR. Samples that tested negative for T. melanosporum or where ectomycorrhizal morphology was not observed were analyzed by sequencing to identify the mycorrhizal fungal symbiont present. The presence of T. melanosporum was detected in all seven orchards. In six orchards, T. melanosporum was detected on all trees, but in only two of fifteen trees in one orchard. Other species of Tuber including T. brennemanii, T. canaliculatum, and T. lyonii, species of Scleroderma, and members of the Pezizales were also detected by sequence analysis. Sporocarps of T. aestivum and T. brumale were found in 2017 and 2018 in separate orchards in North Carolina after the survey was conducted. Overall, results indicate that T. melanosporum has persisted in truffle orchards sampled in North Carolina. Indigenous and contaminating fungal species, including Tuber species, were also detected and present a challenge to the truffle industry in North Carolina.