Fertilisation of Quercus seedlings inoculated with Tuber melanosporum: effects on growth and mycorrhization of two host species and two inoculation methods

Modern truffle cultivation is based on use of inoculated seedlings, which should exhibit highly colonised roots as well as a vegetative quality enhancing field plant performance. However, poor shoot and fine root growth has been a frequent issue in inoculated Quercus seedlings production. Fertilisation is a common solution in forest nurseries, but high fertilisation levels have been found to inhibit the formation of ectomycorrhizas of many fungal species. The influence of slow-release fertilisation (52 mg N, 26 mg P and 36 mg K per seedling) on growth and ectomycorrhizal status of Tuber melanosporum-inoculated seedlings was evaluated. Host species Quercus ilex and Quercus faginea and inoculation methods involving root-dipping and root-powdering were tested. Fertilisation increased weight of both host species without significant detrimental effects on ectomycorrhizal colonisation, showing that it can be effectively used in inoculated seedlings production. Both host species showed similar response to fertilisation. The inoculation method affected seedling weight and ectomycorrhizal status, suggesting that some inoculant carriers are able to damage Quercus development and T. melanosporum colonisation. The study provided an important basis for fine-tuning the use of fertilisers in truffle-inoculated seedling production