Characterization of Tuber indicum (Pezizales, Tuberaceae) mycorrhizae synthesized with four host trees exotic to China

Abstract

The Chinese black truffle Tuber indicum is the main commercial truffle species in China and has strong potential for cultivation. Most studies have focused so far on the production and planting of mycorrhizal seedlings of tree species native to China. Here, we selected four exotic tree species, Quercus pubescens, Q. ilex, Q. palustris and Pinus pinea and inoculated axenically germinated seedlings, five replicates per tree species, with T. indicum spore suspension. As shown by morphological, anatomical and molecular analyses, mycorrhizae were successfully synthesized under greenhouse conditions from 6 months after inoculation and the mycorrhization was stable for at least 24 months in the glasshouse environment. Despite slight morphological variations, T. indicum mycorrhizae were similar on all tree species, i.e. swollen, red-brownish with long hyaline emanating hyphae showing right-angle ramifications. Our observations confirmed the similarity of T. indicum mycorrhizae with those of T. melanosporum regardless of the geographic origin of host trees. Four out of five T. indicum-inoculated pine seedlings were cross-contaminated by T. borchii that was inoculated to another group of P. pinea seedlings raised in the same glasshouse. This is the first study to document the mycorrhization of exotic tree species by T. indicum in China and the first report for Q. palustris. With two successful out of five inoculated seedlings, Q. palustris was less receptive to T. indicum mycorrhization than the other two oak species. Further work is needed to assess whether the T. indicum symbioses obtained here are maintained after planting in the field and if ascomata can be produced by exotic tree species under Chinese environmental conditions.