Sympatric species develop more efficient ectomycorrhizae in the Pinus-Laccaria symbiosis

The mycorrhizal symbiosis is optimal when the plant and the fungi are sympatric. However, in forest plantations the inoculum typically belongs to exotic or allopatric fungi. In this paper, the efficiency of mycorrhization was determined by evaluating the effect of 2 sympatric fungi species (Laccaria trichodermophora and L. bicolor s.l.) and 2 allopatric (L. laccata var. laccata and L. vinaceobrunnea) on the growth and nutrient contents of Pinus montezumae. We also tested the effect of the mycorrhizal helper bacteria P seudomonas fluorescens (Pf_Ag001). After 1 year of growth, we evaluated the mycorrhization percentage, plant height, diameter at root collar, dry weight and nutrient contents (N, P, K) of aerial part and roots. The mycorrhization percentage varied from 93.5% to 98.5%. The treatments that showed higher efficiency (biomass accumulation and K contents) were those inoculated with sympatric species. All Laccaria treatments, either in the presence or absence of the bacteria, showed a better response compared to not inoculated controls. This work demonstrates the significance of using inocula of sympatric species as these are genetically predisposed to associate with their hosts, naturally adapted to the local environmental and edaphic conditions compared with those of allopatric origin.