Genetics of ectomycorrhizal symbiosis

Abstract

SUMMARYThe interactions between genotypes of Pinus elliottii and the ectomycorrhizal fungus Pisolithus tinctorius (Pt) were investigated to assess genetic variability and heritability of root morphology and ectomycorrhizal traits. Seedlings from 15 open‐pollinated pine families, which were either uninoculated or inoculated with Pt and grown under controlled conditions in growth pouches, were analyzed for the following traits: number of shoot roots (SRN), root dry weight (RDW), shoot/root dry weight ratio (SRR), number of ectomycorrhizes (ECN), percentage ectomycorrhizal colonization (ECP) and development of extramatrical mycelium (EMD). There were significant increases in SRN and SRR in inoculated seedlings and significant family variation for RDW and SRR traits. A significant inoculation × family interaction was observed for SRN, but not for RDW and SRR. The individual narrow‐sense heritabilities for SRN, RDW and SRR were, respectively, 0·55, 1·00 and 0·68 (inoculated) and 0·43, 1·00 and 0·25 (uninoculated). The higher heritabilities for the ectomycorrhizal traits were 0·60, 0·81 and 0·53 for ECN, ECP and EMD, respectively. The higher heritabilities of root morphology traits for inoculated seedlings indicates that the mycorrhizal condition of plants should be an important factor in increasing root quality from genetic selection, especially on poor sites where the plants are more dependent on mycorrhizal. The relatively strong genetic control of ectomycorrhizal traits indicates a great potential for selecting individuals in tree breeding programs.