Genetics of ectomycorrhizal symbiosis

Abstract

SUMMARY Seedlings from three open‐pollinated families of Pinus elliottii Engelm. var. elliottii were inoculated with 16 dikaryotic progenies of Pisolithus tinctorius (Pers.) Coker & Couch obtained from controlled crosses between monokaryotic cultures with a tetrapolar mating system. Ninety days after inoculation mycelial strand growth, number of ectomycorrhizas and percentage ectomycorrhizal colonization were assessed. Half‐sib host families and full‐sib fungal progenies differed significantly in all these respects. There were no significant interactions between different genotypes of the two symbionts. The largest proportion of fungal genetic variability was attributable to the non‐additive genetic component. The additive genetic component was significant only for percentage ectomycorrhizal colonization. Mycelial strand growth, number of ectomycorrhizas and percentage colonization had broad‐sense heritabilities of 0·19, 0·29 and 0·23, and narrow‐sense heritabilities of 0·03, 0·00 and 0·15 respectively. These results show that selected Pisolithus strains, obtained from specific crosses, could be used with selected host plants to improve mycelial strand growth and ectomycorrhiza formation in a combined fungal and tree breeding programme.