The Potential Role of Ectomycorrhizal Fungi in Determining Douglas-fir Resistance to Defoliation by the Western Spruce Budworm (Lepidoptera: Tortricidae)

Abstract

There is phenotypic variation among individual trees of interior Douglas-fir (Pseudotsuga menziesii var. glauca [Beissn.] Franco) in their resistance to defoliation by the western spruce budworm (Choristoneura occidentalis Freeman). We evaluated the potential role of ectomycorrhizal fungi in determining this resistance using half-sib seedlings derived from parent trees that are resistant versus susceptible to budworm defoliation in the field. The seedlings were inoculated with Laccaria bicolor ectomycorrhizal fungi, fertilized, or untreated. Approximately 48 d after treatment, late-instar larvae from a nondiapausing laboratory colony of C. occidentalis were allowed to feed on pairs of resistant versus susceptible seedlings for 1 wk. Chemical analyses of current-year shoots for nitrogen (N), phosphorus (P), magnesium (Mg), and zinc (Zn) indicated that the fungus increased foliar concentrations of P and Mg in resistant seedlings, but it did not increase their growth rate. However, L. bicolor had no effect on foliar concentrations of P or Mg in susceptible seedlings, even though seedling growth rates increased slightly in response to the inoculation. L. bicolor had no effect on foliar levels of N or Zn in any of the seedlings. As expected, fertilization increased levels of N and P in the foliage of both resistant and susceptible seedlings, but it did not affect levels of Mg and Zn. Surprisingly, the fertilizer treatment had no effect on seedling growth rates. Despite these differences, late-instar budworms showed no feeding preference among untreated, mycorrhizal, or fertilized seedlings. The fact that seedlings from resistant versus susceptible Douglas-firs responded differently to the L. bicolor treatment lends preliminary support to the hypothesis that ecotmycorrhizae might play a role in Douglas-fir resistance to damage from the western spruce budworm. Finally, differences in foliar concentrations of N and P among untreated seedlings from different maternal trees suggested that foliar nutritional chemistry is influenced by the tree's genotype.

Effects of mycorrhizal fungi on insect herbivores: a meta‐analysis

“…(2) Plants had been randomly allocated to mycorrhizal treatments and mycorrhizal effects were not confounded by other factors. Based on this criterion, we excluded the study by Palermo et al (2003) in which the comparison between mycorrhizal and non-mycorrhizal trees was confounded by differences in plant genotypes (resistant or susceptible to herbivory). (3) Insect herbivore performance, density, and/or degree of damage were assessed on control and experimental plants.…”

Maintenance of host specialisation gradients in ectomycorrhizal symbionts

“…Other functions should also be considered as targets of selection for specialisation, and these may relate to specific environmental contexts. For example, ECM may enhance plant defence (Palermo et al ., 2003) and resistance to attack, water uptake (Marjanovic et al ., 2005), trace element capture (Gil‐Martinez et al ., 2018) and resistance to toxic pollutants (Gil‐Martinez et al ., 2018; Branco et al ., 2022).…”

“…Other functions should also be considered as targets of selection for specialisation, and these may relate to specific environmental contexts. For example, ECM may enhance plant defence (Palermo et al, 2003) and resistance to attack, water uptake (Marjanovic et al, 2005) resistance to toxic pollutants (Gil-Martinez et al, 2018;Branco et al, 2022). Finally, evolution of host specialisation gradients may also be driven by exchange of non-nutritional molecules, such as those related to defence and immunity, but which are likely linked to the provision of energy (carbon) by hosts.…”

Principles and strategies of biological control economically harmful forest organisms

“…У природним условима, микоризне гљиве имају значајно мјесто у биолошком сузбијању појединих фитопатогених микроорганизама (нпр. гљива из родова Rhizoctonia, Fusarium, Phytophthora, Heterobasidion, Armillaria, Sphaeropsis) (Guenoune et al 2001;Palermo et al 2003;Luoma and Eberhart 2006;Riedlinger et al 2006;Montecchio et al 2009;Scatolin et al 2012). Duchesne (1994)…”