Mycorrhization of pecans with European truffles (Tuber spp., Tuberaceae) under southern subtropical conditions

Abstract

Pecan trees are known to form ectomycorrhizae with a wide range of fungi, including commercial truffles that can be cultivated in agroforestry systems. Here, we investigated whether pecans can be successfully mycorrhized by Tuber spp. and whether the mycorrhization affects growth parameters and nutrient content of two productive pecan cultivars under southern subtropical conditions. We also sought to define procedures of mycorrhization adapted to the subtropics. The seedlings of two pecan cultivars (Barton and Importada) were inoculated with both Tuber aestivum and T. brumale and grown in a nursery for 12 months. The levels of ectomycorrhizal colonization and the morphological and chemical parameters of the seedlings were analyzed. The proposed mycorrhization protocol was successful, as all truffle-inoculated seedlings exhibited a high percentage of mycorrhized fine roots, on average 70% with T. aestivum and 88% with T. brumale. In both pecan cultivars, mycorrhization by the Tuber species reached levels at which all seedlings would qualify as suitable for commercialization. Notably, the cultivar Barton inoculated with T. brumale exhibited higher total biomass accumulation and growth of roots and shoots. Shoot and root parameters did not show nutrient deprivation. The nutrient status after one year of cultivation in a nursery also supported that the applied protocol was adequate to maintain healthy mycorrhized seedlings with suitable nutritional status for out-planting of seedlings in a commercial plantation. To our knowledge, this is the first study on the mycorrhization of pecan seedlings with European truffles under southern subtropical conditions. Our results suggested that the tested cultivars have a high potential for truffle production considering the necessary substrate, site, and management adaptations for selected commercial truffle species and the requirements for pecan orchards.