Interactions of the white truffle Tuber magnatum Picco with bacteria and plants

The white truffle (Tuber magnatum Picco) is a highly valuable food product, yet its cultivation remains underdeveloped. Despite numerous attempts, production still depends on natural truffle grounds due to limited knowledge of its biology and ecology. This study aims to summarize existing literature and address key knowledge gaps. The thesis comprises seven chapters. Chapter 1 introduces T. magnatum morphology, aroma, biology, ecology, natural production, and cultivation. Chapter 2 outlines the objective: to elucidate ecological traits of T. magnatum to advance cultivation techniques. Chapter 3 investigates interactions between T. magnatum mycelium and bacteria through in vitro mycelial cultivation. Isolation and phylogenetic analyses identified Bradyrhizobium bacterial strains promoting T. magnatum mycelium growth in vitro, highlighting a dependency not observed in other Tuber species. Chapter 4, in collaboration with Michigan State University, presents comparative genome analyses of two Bradyrhizobium strains associated with T. magnatum mycelium. Phylogenomic reconstruction was conducted to compare Bradyrhizobium genomes across supergroups. Chapter 5 employs Tuber borchii Vittad. as a model to explore endophytic behavior between truffles and herbaceous plants. A study using morphological and molecular techniques detected T. borchii mycelium within wild orchid roots, suggesting orchids as temporary hosts facilitating survival and lifecycle progression. Chapter 6 extends this method to T. magnatum, analyzing endophytic behavior in ECM and non-ECM host plants. Fluorescent In Situ Hybridization (FISH) and PCR detected T. magnatum in plant roots, but FISH confirmed colonization in only one sample, indicating rare and seasonal endophytic interactions. Chapter 7 concludes with findings and future research directions. This study enhances understanding of T. magnatum ecology, informing potential advancements in its cultivation.