Sustained ascoma production and reproductive dynamics of the Asian black truffle Tuber himalayense in Japan

The Asian black truffle Tuber himalayense is commercially harvested from natural habitats. However, its populations have declined since the 1990s owing to habitat degradation and overharvesting. To ensure sustainable production and to conserve wild genetic resources, cultivation and a better understanding of reproductive dynamics are essential. We inoculated Quercus serrata seedlings with T. himalayense ascospores sourced from two localities and planted into a nursery in Japan. After 7½ years, two ascomata appeared, followed a year later by 12 more. To confirm their identity, we performed molecular phylogenetic analysis by using the rDNA internal transcribed spacer region and multilocus genotyping with 13 simple sequence repeat (SSR) markers. All ascomata matched one inoculated strain. Further analysis of SSR and mating type markers from spore and gleba DNAs showed that all ascomata were homozygotes. This study marks the first successful cultivation of T. himalayense in Japan. It also provides rare data on mating dynamics from the first year of ascoma formation-an aspect rarely captured in Tuber studies.