Ectomycorrhizal Fungus Laccaria Laccata Research Articles

Diversity and growth-effects of ectomycorrhizal fungi of a Nothofagus pumilio forest in the Andes of Southern Chile

Chilean temperate rainforests have unique climatic, edaphic and biotic conditions, constituting pre-industrial blueprint ecosystems. Mycorrhizal associations play a central role in the biogeochemical processes of these ecosystems´ functioning. Baseline forest ecology studies are necessary in order to better understand diversity patterns, specifically regarding mycorrhizal symbiosis. Therefore, here we described the vegetation characteristics and the mycorrhizal relationships of vascular plants in a Nothofagus pumilio forest. We also described, via morphological methods, the ectomycorrhizal diversity present in this forest. Additionally, we determined whether ectomycorrhizal inoculations confer positive growth effects on N. pumilio seedlings. We founded that from 46 described vascular plant species, 42 (91%) were associated with mycorrhizae and of these 33 (72%) were associated with arbuscular mycorrhizae (AM), two (the dominant trees N. pumilio and N. dombeyi ) were associated with ectomycorrhizae (EM), five were associated with ericoid mycorrhizae, two with orchid mycorrhizae, and four were non-mycorrhizal. Additionally, 26 EM species were detected of which 14 belong to Cortinarius . Finally, there were clear differences in the growth of N. pumilio seedlings inoculated with the ectomycorrhizal fungus Laccaria laccata compared to non-inoculated plants. We suggest that mycorrhizal fungi play a key role in seedling colonization of extreme environments such as the Andean treeline.

Agrobacterium tumefaciens-mediated genetic transformation of the ectomycorrhizal fungus Laccaria laccata

Ectomycorrhizal fungi form symbiotic relationships with the roots of most tree species and support increased forest health and productivity. The ectomycorrhizal fungus Laccaria laccata was successfully transformed through Agrobacterium tumefaciens-mediated transformation (ATMT). We observed a transformation efficiency of 80 %, with 100 % of the assessed transformants exhibiting mitotic stability after five passages in culture medium without the selective agent. The amplification of the 626-bp DNA fragment corresponding to the hygromycin B phosphotransferase (hph) gene and a Southern blotting analysis showed that the assessed transformants had integrated the T-DNA into the genome, confirming the success of the ATMT procedure. Single T-DNA integrations were detected in five of the eight transformants assessed by Southern blotting, and the hybridization pattern confirmed that the integration occurred randomly in the genome of the fungus. The development of an efficient ATMT system that allows the integration of single T-DNA copies into the L. laccata genome makes functional genetic studies in this ectomycorrhizal fungus feasible.

The effects of insect pathogenic soil fungi and ectomycorrhizal inoculation of birch seedlings on the survival of Otiorhynchus larvae

Weevil larvae of the genus Otiorhynchus are a serious problem in agriculture and forestry, causing damage to a wide range of plant species, primarily by larval feeding on roots. Otiorhynchus larvae are a serious pest in forest plantations in Iceland, causing 10–20% mortality of newly‐planted seedlings. We studied the effects of soil fungi on the survival of Otiorhynchus sulcatus larvae. The larvae were introduced into pots with birch seedlings grown in: (i) nursery peat; (ii) nursery peat inoculated with three different species of ectomycorrhizal fungi; (iii) nursery peat inoculated with insect pathogenic fungi; (iv) nursery peat inoculated with ectomycorrhizal fungi and insect pathogenic fungi; and (v) nursery peat inoculated with natural forest soil from Icelandic birch woodland. Larval survival was negatively affected by inoculation of: (i) the ectomycorrhizal fungus Laccaria laccata; (ii) the ectomycorrhizal fungus Cenococcum geophylum; (iii) the insect pathogenic fungus Metarhizium anisopliae; and (iv) forest soil. Inoculation with the ectomycorrhizal fungus Phialophora finlandia did not have any significant effect on larval survival. No significant synergistic effect was found between insect pathogenic and ectomycorrhizal fungi. It is concluded that ectomycorrhizal and insect pathogenic fungi have a significant potential in biological control of Otiorhynchus larvae in afforestation areas in Iceland. Further studies are needed to establish the effect of these fungi in the field and to analyse how mycorrhizal fungi affect root‐feeding larvae.

Influence of the ectomycorrhizal fungus Laccaria laccata on pre-emergence, post-emergence and late damping-off by Fusarium oxysporum and F. verticillioides on Stone pine seedlings

In greenhouse experiments, the ectomycorrhizal fungus Laccaria laccata was evaluated for biological control of preemergence, post-emergence and late damping-off of Pinus pinea caused by Fusarium verticillioides and F. oxysporum. In pre-emergence damping-off assays, preinoculation with Laccaria laccata did not significantly improve germination of seeds and no statistical significant differences were found in Fusarium treatments when compared with controls. At 18 weeks after sowing, inoculation with L. laccata reduced the incidence of post-emergence damping-off but differences were significant only in F. oxysporum treatments. Pinus pinea transplanted plants were used in late damping off assays, and only F. oxysporum produced significant damage. Inoculation with L. laccata did not attenuate significantly the virulence of F. oxysporum. However, the percentage of mycorrhization did not reached significant level, so the amount of mycorrhizal fungus was insufficient for effective protection. Although very low percentages of mycorrhization were recorded in all mycorrhized treatments, and Fusarium occurrence significantly reduced mycorrhization, those levels have been efficient to reduce damage in F. oxysporum post-emergence damping-off assays. In short, pre-emergence damping-off was not found; only F. oxysporum produced significant damage on P. pinea seedlings and L. laccata reduced damage when the percentage of mycorrhization reached a significant level. These results have been compared with previous work on P. sylvestris inoculated with the same mycorrhizae isolate and Fusarium pathogens.

Ultrastructural and cytochemical aspects of the interaction between the ectomycorrhizal fungus Laccaria laccata and the saprotrophic fungi, Trichoderma harzianum and T. virens

Different interactions between soil fungi competing in the rhizosphere with each other are necessary to understand their influence on plant growth and health. The interactions between the ectomycorrhizal (ECM) fungus Laccaria laccata and soil saprotrophic fungi (T. harzianum, T. virens) were studied by transmission electron microscopy, and by gold cytochemistry to assess the potential role of cell wall lytic enzymes in mycoparasitism. Anti-β-1,3-glucan antibody, WGA/ovomucoid–gold complex and PATAg test were used to localize β-1,3-glucan, chitin and polysaccharides. Cytoplasm disorganisation of the saprotrophic fungi occurred concurrently with dissolution of β-1,3-glucan in walls of hyphae and conidia of the saprotrophic fungi. Then digestion of polysaccharides and chitin of colonised fungal structures occurred. The studies suggest sequential contribution of cell wall lytic enzymes and importance of disturbing the host's cell integrity during mycoparasitism. We conclude that the ECM fungus can parasitise on the saprotrophic fungi not only in dual culture on artificial medium but also in the rhizosphere of Scots pine.

In vitro evidence of mycoparasitism of the ectomycorrhizal fungus Laccaria laccata against Mucor hiemalis in the rhizosphere of Pinus sylvestris

Interactions between the ectomycorrhizal fungus Laccaria laccata and the soil fungus Mucor hiemalis f. hiemalis in co-culture, and in the rhizosphere of in vitro-grown Pinus sylvestris seedlings were investigated by light- and scanning electron-microscopy. In co-culture, mycelial growth away from the L. laccata colony reduced the number of aerial hyphae at the contact zone and increased the density and compactness of the mycelium-characterized gross morphology of the saprobic fungus. Although the growth of M. hiemalis was suppressed, no penetration of M. hiemalis hyphae after the colony was entered by L. laccata was observed. Instead, dense coiling of L. laccata hyphae around sporangiophores, overpowering them and causing them to disappear, was quite common. On nonmycorrhizal roots, sporangiospores germinated heavily and formed long hyphae for 2 days post inoculation, whereas their germination was totally inhibited on mycorrhizal roots. At 3 days after inoculation, only sporangia were seen with mycelial mats firmly attached to the roots by the mantle hyphae, whereas some remnants of sporangiophores, ruptured sporangial walls and degraded hyphae of M. hiemalis were overgrown by the mantle hyphae. During the next 3 days, the mantle-hyphae-invading sporangia formed short, thin branches that grew directly towards individual spores, tapering off upon contact.

Growth response of Populus trichocarpa to inoculation by the ectomycorrhizal fungus Laccaria laccata in a pot and a field experiment

The growth response of Populus trichocarpa cv. Muhle Larsen to inoculation by the ectomycorrhizal (ECM) fungus Laccaria laccata was investigated in a pot and a field experiment on arable soils. Non-sterilized soil from a Cambisol in Wildeshausen (Lower Saxonia, Germany) was taken for the pot experiment. The field experiment was established at a reforestation plantation on Stagnic Gleysols in Leubnitz (Saxonia, Germany). Both arable soils were assumed to be low in indigenous ECM inoculum caused by the lack of host plants. The study was designed to determine (1) the ECM colonization on the poplar clone with or without inoculation in the pot and in the field experiment and (2) the effects of inoculation on plant growth parameters. In the pot experiment, 7% of fine roots of non-inoculated control plants and 18% of inoculated test plants were colonized with ECM fungi after one growing season. In the field experiment, 6% of fine roots were colonized with ECM fungi at the control plot and 20% at the inoculated plot after the first growing season. After the second growing season 50 or 53% were colonized, respectively. The inoculation by L. laccata caused significantly increased shoot lengths and leaf potassium concentrations of the poplar clone in the pot and field experiment after the first growing season. In the second growing season, only the leaf potassium concentrations were further increased compared to the non-inoculated control plants. The density of VAM spores in the soil and the leaf nitrogen, magnesium and calcium concentrations were significantly reduced after inoculation. However, after the second growing season there were no longer were significant differences in the ECM colonization and shoot lengths of inoculated or non-inoculated poplar cuttings. The results indicated that inoculation can be successfully used to increase ECM colonization and growth rates of P. trichocarpa on former arable soils in the first growth period. This could increase the resistance of the cuttings to soil-borne pathogens and their competitiveness for nutrients and space against weeds.

Interaction between Laccaria laccata and Trichoderma virens in co-culture and in the rhizosphere of Pinus sylvestris grown in vitro.

Interactions between the ectomycorrhizal fungus Laccaria laccata and the soil fungus Trichoderma virens in co-culture and in the rhizosphere of Pinus sylvestris seedlings growing in vitro were investigated by light and scanning electron microscopy. The growth of T. virens was inhibited in co-culture. Shortened, more branched and sometimes deformed or injured hyphae of T. virens were observed in the zone of inhibition. Two-month-old mycorrhizae of P. sylvestris/ L. laccata were inoculated with a conidial suspension of T. virens and examined at intervals of 7-24 h and 2, 3, and 6 days post-inoculation (p.i.). On non-mycorrhizal roots, conidia germination was high and long hyphae formed 3 days p.i. On mycorrhizal roots, short germ tubes were observed only sporadically. At 3 days p.i., the mantle hyphae of L. laccata grew towards the conidia and coiled around them. Extremely dense coils of hyphae were found around clusters of conidia. Deformation of conidia, breaks in conidial walls and their partial degradation were observed 6 days p.i.

Effect of Electric Impulse on Sporocarp Formation of Ectomycorrhizal Fungus Laccaria laccata in Japanese Red Pine Plantation

We examined the effect of electric impulses on sporocarp formations of ectomycorrhizal fungus in a Japanese red pine (Pinus densiflora) plantation.Laccaria laccata was the dominant species in this study plantation. Spatial distribution concentrated in the electric impulse treatment zone, and recorded a markedly larger number of sporocarps compared with untreated control plots. The effect of electric impulses was also recognized onL. laccata fruiting with a mycorrhizal sapling in a pot. Sporocarp production ofL. laccata was strongly promoted by the electric impulse in experiments bothin vivo natural plantation stands andin vitro pot saplings. Our work indicates the possibility of enhancement of sporocarp production of the mycorrhizal fungi with electric impulses in the nursery and plantation.

Sulphate uptake and xylem loading of mycorrhizal beech roots.

Beech nuts (Fagus sylvatica L.) were germinated and grown in soil inoculated with the ectomycorrhizal fungus Laccaria laccata or Paxillus involutus for 18-20 wk. The success of mycorrhizal infection was monitored by measuring the ergosterol contents of the mycorrhizas. Ergosterol levels ranged from 122±23 μg g-1 d. wt (Laccaria mycorrhizas) to 94±36 μg g-1 d. wt (Paxillus mycorrhizas), indicating that ectomycorrhizal symbiosis was established. In root incubation chambers, rates of sulphate uptake and the xylem loading of sulphate of excised mycorrhizas were investigated. Both types of mycorrhizas showed saturation kinetics in external sulphate concentrations from 2·5-1000 μmol l-1 . Linearization of these kinetics revealed two phases with low apparent Km (Laccaria mycorrhizas: 15±3 μmol l-1 ; Paxillus mycorrhizas: 13±3 μmol l-1 ) and Vmax (Laccaria mycorrhizas: 19±3 nmol h-1 g-1 f. wt; Paxillus mycorrhizas: 25±4 nmol h-1 g-1 f. wt) at low external sulphate concentrations and significantly higher kinetic constants at higher sulphate supplies. Relative xylem loading, i.e. the portion of sulphate loaded into the xylem that was taken up, remained constant over the entire concentration range investigated (c. 4-7% of the sulphate taken up). If trees were supplied for 72 h with different N and sulphur concentrations, both uptake of sulphate and relative xylem loading were unaffected by sulphur availability, but modulated by N supply. Nitrogen depletion diminished the rates of sulphate uptake in Laccaria and Paxillus mycorrhizas. In response to higher N availability combined with sulphur depletion, sulphate uptake of Laccaria mycorrhizas, but not of Paxillus mycorrhizas, increased. Organic compounds considered to be possible signals for the regulation of sulphate uptake were fed to excised mycorrhizas. l-Cysteine but not l-methionine and glutathione (γ-Glu-Cys-Gly) inhibited sulphate uptake of the two mycorrhizas and xylem loading of sulphate was stimulated rather than inhibited by l-Cys in both types. In Paxillus mycorrhizas glutathione had a similar effect. O-Acetyl-l-serine (OAS), a precursor of l-cysteine, stimulated sulphate uptake, but did not affect xylem loading. Apparently, OAS, generated in N metabolism, and l-cysteine, a product of assimilatory sulphate reduction, act as antagonists, together mediating regulation of sulphate uptake.

Interactive effects of mycorrhization and elevated atmospheric CO2 on sulphur nutrition of young pedunculate oak (Quercus robur L.) trees

ABSTRACTPedunculate oak (Quercus robur L.) was germinated and grown at ambient CO2 concentration and 650 μmol mol−1 CO2 in the presence and absence of the ectomycorrhizal fungus Laccaria laccata for a total of 22 weeks under nonlimiting nutrient conditions. Sulphate uptake, xylem loading and exudation were analysed in excised roots. Despite a relatively high affinity for sulphate (KM= 1.6 mmol m−3), the rates of sulphate uptake by excised lateral roots of mycorrhizal oak trees were low as compared to herbaceous plants. Rates of sulphate uptake were similar in mycorrhizal and non‐mycorrhizal roots and were not affected by growth of the trees at elevated CO2. However, the total uptake of sulphate per plant was enhanced by elevated CO2 and further enhanced by elevated CO2 and mycorrhization. Sulphate uptake seemed to be closely correlated with biomass accumulation under the conditions applied.The percentage of the sulphate taken up by mycorrhizal oak roots that was loaded into the xylem was an order of magnitude lower than previously observed for herbaceous plants. The rate of xylem loading was enhanced by mycorrhization and, in roots of mycorrhizal trees only, by growth at elevated CO2. On a whole‐plant basis this increase in xylem loading could only partially be explained by the increased growth of the trees. Elevated CO2 and mycorrhization appeared to increase greatly the sulphate supply of the shoot at the level of xylem loading. For all treatments, calculated rates of sulphate exudation were significantly lower than the corresponding rates of xylem loading of sulphate. Radiolabelled sulphate loaded into the xylem therefore seems to be readily diluted by unlabelled sulphate during xylem transport.Allocation of reduced sulphur from oak leaves was studied by flap‐feeding radiolabelled GSH to mature oak leaves. The rate of export of radioactivity from the fed leaves was 4–5 times higher in mycorrhizal oak trees grown at elevated CO2 than in those grown at ambient CO2. Export of radiolabel proceeded almost exclusively in a basipetal direction to the roots. From these experiments it can be concluded that, in mycorrhizal oak trees grown at elevated CO2, the transport of sulphate to the shoot is increased at the level of xylem loading to enable increased sulphate reduction in the leaves. Increased sulphate reduction seems to be required for the enhanced allocation of reduced sulphur to the roots which is observed in trees grown at elevated CO2. These changes in sulphate and reduced sulphur allocation may be a prerequisite for the positive effect of elevated CO2 on growth of oak trees previously observed.

Interactive effects of mycorrhization and elevated carbon dioxide on growth of young pedunculate oak (Quercus robur L.) trees

Pedunculate oak (Quercus robur L.) was germinated and grown at ambient CO2 level and 650 ppmv CO2 in the presence and absence of the ectomycorrhizal fungus Laccaria laccata for a total of 6 month under nutrient non-limiting conditions. Mycorrhization and elevated atmospheric CO2 each supported the growth of the trees. Stem height, stem diameter, and dry matter accumulation of pedunculate oak were increased by mycorrhization. Elevated atmospheric CO2 enhanced stem height, stem diameter, fresh weight and dry weight, as well as lateral root formation of the trees. In combination, mycorrhization and elevated atmospheric CO2 had a more than additive, positive effect on tree height and biomass accumulation, and further improved lateral root formation of the trees. From these findings it is suggested that the efficiency of the roots in supporting the growth of the shoot is increased in mycorrhized oak trees at elevated atmospheric CO2.

Rhizodeposition and net release of soluble organic compounds by pine and beech seedlings inoculated with rhizobacteria and ectomycorrhizal fungi

A lysimetric experiment was performed in a greenhouse to evalute root deposition and net release of soluble organic compounds after 1 and 2 years from pine and beech seedlings inoculated with an ectomycorrhizal fungus (Laccaria laccata) and/or rhizobacteria (Agrobacterium radiobacter for beech and Agrobacterium sp. for pine). Total C compounds released in the rhizosphere of both plants increased after inoculation with the bacteria or ectomycorrhizal fungus. The rhizobacteria increased root and plant growth and rhizodeposition, but the mycorrhizal fungi appeared to increase only root deposition. Soluble C compounds, collected after 2 years, represented only 0.1–0.3% of the total C compounds released into the rhizosphere, and were modified by inoculation with the microorganisms. After inoculation with the bacteria, levels of sugars and amino acids decreased in pine and beech rhizospheres, whereas organic acids increased, especially in the pine rhizosphere. In the rhizosphere of mycorrhizal beeches, sugar and amino acids increased, and organic acids differed from those released from non-mycorrhizal beeches. In the mycorrhizal pine rhizosphere, however, all compounds decreased. Following dual inoculations, mycorrhizal colonization increased, no effect on plant growth was observed, and virtually no organic acids were detected.

Purification and Characterization of Glutamine Synthetase and NADP-Glutamate Dehydrogenase from the Ectomycorrhizal Fungus Laccaria laccata

Glutamine synthetase (GS) and NADP-dependent glutamate dehydrogenase (NADP-GDH) play a key role in nitrogen assimilation in the ectomycorrhizal fungus Laccaria laccata (Scop. ex Fr. Cke) strain S 238. The two enzymes were purified to apparent electrophoretic homogeneity by a three-step procedure involving diethylaminoethyl (DEAE)-Trisacryl and affinity chromatography, and DEAE-5PW fast protein liquid chromatography. This purification scheme resulted in a 23 and 62% recovery of the initial activity for GS and NADP-GDH, respectively. Purified GS had a specific activity of 713 nanomoles per second per milligram protein and a pH optimum of 7.2. Michaelis constants (millimolar) for the substrates were NH(4) (+) (0.024), glutamate (3.2), glutamine (30), ATP (0.18), and ADP (0.002). The molecular weight (M(r)) of native GS was approximately 380,000; it was composed of eight identical subunits of M(r) 42,000. Purified NADP-GDH had a specific activity of 4130 nanomoles per second per milligram protein and a pH optimum of 7.2 (amination reaction). Michaelis constants (millimolar) for the substrates were NH(4) (+) (5), 2-oxoglutarate (1), glutamate (26), NADPH (0.01), and NADP (0.03). Native NADP-GDH was a hexamer with a M(r) of about 298,000 composed of identical subunits with M(r) 47,000. Polyclonal antibodies were produced against purified GS and NADP-GDH. Immunoprecipitation tests and immunoblot analysis showed the high reactivity and specificity of the immune sera against the purified enzymes.

Effect of dual inoculation of Douglas fir with the ectomycorrhizal fungus Laccaria laccata and mycorrhization helper bacteria (MHB) in two bare-root forest nurseries

Douglas fir (Pseudotsuga menziesii) seedlings in two bare-root forest nurseries were inoculated with the ectomycorrhizal fungus Laccaria laccata, together or not with one of five mycorrhization helper bacteria isolated from L. laccata sporocarps or mycorrhizas and previously selected by in vitro and glasshouse screenings. With the most efficient MHB isolates, when compared to the control with no bacteria, the percent of mycorrhizal short roots was increased from 60 to 90 or from 80 to 100, depending on the nursery, with inoculation doses as low as 106 living cells per m2. A dual inoculum made of calcium alginate beads containing the two microorganisms appears to be a valuable technique for increasing the efficiency of ectomycorrhizal inoculation of planting stocks in forest nurseries.

Effect of dose and formulation of Laccaria laccata inoculum on mycorrhizal infection and growth of Douglas fir in a nursery

A fumigated nursery bed on a sandy loam was inoculated with the ectomycorrhizal fungus Laccaria laccata and seeded with Douglas fir. Two types of inoculum were compared: mycelium grown in a vermiculite/peat mixture, and mycelium grown in liquid medium and entrapped in a calcium alginate gel with different quantities of mycelium. At the end of the first growing season, the alginate inoculum at the dose of 5 g mycelium (dry weight) per m 2 proved to be the most efficient. The top dry weight of the seedlings in this treatment was 2.3 fold that of the non-inoculated fumigated controls. This inoculation treatment also ensured nearly total mycorrhizal infection by L. laccata.

Effect of fertilization on seedling growth, ectomycorrhizal symbiosis, and nutrient uptake in Larixlaricina

Container-grown Larixlaricina (Du Roi) K. Koch seedlings were inoculated with the ectomycorrhizal fungus Laccarialaccata (Scop, ex Fr.) Berk and Br. and grown under two levels of slow-release fertilizer (Osmocote) or two levels of soluble fertilizer (N–P–K). Nonmycorrhizal seedlings grew better under high fertility regimes, whereas no significant differences were observed between low and high fertility levels for the mycorrhizal seedlings. Mycorrhizal seedlings had significantly greater root length, total biomass, and a lower shoot:root ratio under all fertility treatments. Ectomycorrhizal development was excellent regardless of fertilizer treatment. Nitrogen, P, K, Ca, and Mg concentrations were significantly higher in the mycorrhizal seedlings than in the nonmycorrhizal seedlings under all fertility regimes.

Interactions betweenLaccaria laccata, Agrobacterium radiobacter and beech roots: Influence on P, K, Mg, and Fe mobilization from minerals and plant growth

Fagus silvatica L. inoculated or not with the ectomycorrhizal fungusLaccaria laccata and/or a phosphate-solubilizing rhizobacterium,Agrobacterium radiobacter, was cultivated in a greenhouse in lysimeter cylinders containing rock phosphate and a mica (phlogopite) as the only sources of P, Fe, Mg and Al. After two years, beech dry matter and P, Mg, Fe and K uptake were higher for plants inoculated—either withAgrobacterium radiobacter or withLaccaria laccata, but not for those plants inoculated with both micro-organisms—than for uninoculated plants. Mineral element mobilization from rock phosphate and from phlogopite was also greater when plants were inoculated with the bacteria or with the ectomycorrhizal fungi. Such mineral element dissolution can be related to the increased root growth but also to the amount of organic acids released in the rhizosphere. The absence of significant effects of dual inoculation suggested competition between micro-organisms.

Effect of aminocyclopropane carboxylic acid and aminoethoxyvinylglycine on ethylene production by ectomycorrhizal fungi

Aminoethoxyvinylglycine, an inhibitor of ethylene production in higher plants, does not inhibit methionine-induced ethylene production by the ectomycorrhizal fungus Laccaria laccata (Scop, ex Fr.) Berk. & Br. Aminocyclopropane carboxylic acid is not a precursor of ethylene formation by L. laccata or Hebeloma crustiliniforme.

Use of the ectomycorrhizal fungus Laccarialaccata in forestry. II. Effects of fertilizer forms and levels on ectomycorrhizal development and growth of container-grown Douglas-fir and ponderosa pine seedlings

Container-grown Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) and ponderosa pine (Pinusponderosa Dougl. ex Laws.) were inoculated with the ectomycorrhizal fungus Laccarialaccata (Scop, ex Fr.) Berk, and Br. and grown under three levels of soluble fertilizer (low, high, and a combination of low changed to high) and full and half strength of a slow-release fertilizer. Ectomycorrhiza development was excellent for both hosts regardless of fertilizer treatment; percent ectomycorrhizal short roots averaged 93.6 for Douglas-fir and 94.5 for ponderosa pine. Inoculation did not affect the size of Douglas-fir but significantly reduced growth of ponderosa pine under low fertility. L. laccata performed well under high-fertility regimes; production of outplantable nursery stock with well-developed ectomycorrhizae was obtained.