Characterization and classification of mycorrhizae of Douglas fir. II. Pseudotsuga menziesii + Rhizopogon vinicolor

Abstract

A common tuberculate ectomycorrhiza of Douglas fir in the Pacific Northwest, described earlier by Trappe, is further examined and defined. Tubercles consist of an outer rind of aseptate, amber, thick-walled hyphae encasing tightly packed inner elements mantled with septate, hyaline, thin-walled hyphae. Reported as a Phycomycete and a Basidiomycete, respectively, the two hyphal forms actually belong to a single fungus, Rhizopogon vinicolor A. H. Smith; cultural characteristics of this fungus are described. Pure culture mycorrhiza syntheses with both mycorrhizal and sporocarpic isolates and Douglas-fir seedlings are reported. Antagonism tests revealed the following inhibition of root pathogens by R. vinicolor: strong—Phytophthora cinnamomi Rands, Pythium debaryanum Heese, and Pythium sylvaticum Campbell & Hendrix; moderate—Fomes annosus (Fr.) Cke. and Poria weirii Murr.; and weak or none— Fusarium oxysporum f. pini (Hartig) Snyd. & Hans., Pythium ultimum Trow, Rhizoctonia solani Kuehn, and Macrophomina phaseoli (Maubl.) Ashby.

Comparative anatomy of ectomycorrhizas synthesized on Douglas fir by Rhizopogon spp. and the hypogeous relative Truncocolumella citrina

“…Rhizopogon vinicolor and R. parksii produced ectomycorrhizas with mostly single monopodial to pinnate morphology, but the tuberculate morphology, a type frequently seen on field material (Zak, 1971 ;Massicotte et al, 1992 ;Goodman, 1996) was absent. Rhizopogon subcaerulescens -Douglas-fir ectomycorrhizas were of a monopodial morphology.…”

Biology of the ectomycorrhizal fungal genus, Rhizopogon

“…In Pacific Northwest forests dominated by Pseudotsuga menziesii (Douglas fir), several section Villosuli species occur on seedlings as well as on young and ancient trees (Trappe, 1965 ;Zak, 1971 ;Alvarez & Linderman, 1983 ;Castellano, 1987 ;Borchers & Perry, 1990 ;Massicotte et al, 1992Massicotte et al, , 1994Miller et al, 1992 ;Smith et al, 1995). Several section Villosuli species also co-occur with Pseudotsuga menziesii in exotic plantations in Europe (Gross et al, 1980 ;Jansen & de Vries, 1989 ;Parlade!…”

“…This feature, along with the characteristic yellow colour, makes the species readily identifiable in field collections. Other Rhizopogon species have induced tuberculate (Zak, 1971) or coralloid (Agerer et al, 1996) ectomycorrhizas, and many other fungal genera induce tuberculate clusters on a variety of hosts (Massicotte et al, 1992).…”

Ectomyeorrhiza formation in Eucalyptus

“…The mature tuberculate mycorrhiza of Eucalyptus pilularis resembles in general morphology a tuberculate mycorrhiza formed in an association between Rhizopogon and Douglas fir (Zak, 1971). There are some differences, however, in the arrangement of the roots and structure of the internal rhizomorphs.…”

“…Enclosing the mycorrhizas within the rind of the tubercle may reduce such contact to rhizomorphs or mycelial cords which connect the tuberculate ectomycorrhizas with mycelial fans in the soil (Trappe, 1965). Zak (1971) has suggested that the tubercles may protect the mycorrhizas from attack by pathogens and sap-sucking insects.…”