Tuber melanosporum drives the symbiosis with Castanea sativa seedlings under greenhouse conditions and high calcium levels

The sweet chestnut ( Castanea sativa ) could potentially be used as a host for the Périgord truffle (Tuber melanosporum ) in multi-cropping plantations to promote rural or marginalized economies by providing farmers with a valuable source of income from both the truffle and the chestnut. Black truffles are known to associate to sweet chestnut trees in the wild. However, inoculation of chestnut seedlings with this highly appreciated edible fungus has not been attempted so far under greenhouse conditions. In this study, we tested the suitability of C. sativa as a host for T. melanosporum using a substrate containing high levels of active calcium (Ca 2+ ) to enhance truffle growth. We found that C. sativa seedlings can be successfully colonized by T. melanosporum in the nursery and that T. melanosporum appears to have a strong influence in its host’s physiology, growth, and nutritional processes. The inoculated plants showed a greater root dry weight, water potential values and higher Ca 2+ content. Under these conditions and using a substrate containing limestone seems to favour the fungus in the mutualistic symbiosis.