title: Ecto- and arbuscular mycorrhizal symbiosis can induce tolerance to toxic pulses of phosphorus in jarrah (Eucalyptus marginata) seedlings.
abstract: In common with many plants native to low P soils, jarrah (Eucalyptus marginata) develops toxicity symptoms upon exposure to elevated phosphorus (P). Jarrah plants can establish arbuscular mycorrhizal (AM) and ectomycorrhizal (ECM) associations, along with a non-colonizing symbiosis described recently. AM colonization is known to influence the pattern of expression of genes required for P uptake of host plants and our aim was to investigate this phenomenon in relation to P sensitivity. Therefore, we examined the effect on hosts of the presence of AM and ECM fungi in combination with toxic pulses of P and assessed possible correlations between the induced tolerance and the shoot P concentration. The P transport dynamics of AM (Rhizophagus irregularis and Scutellospora calospora), ECM (Scleroderma sp.), non-colonizing symbiosis (Austroboletus occidentalis), dual mycorrhizal (R. irregularis and Scleroderma sp.), and non-mycorrhizal (NM) seedlings were monitored following two pulses of P. The ECM and A. occidentalis associations significantly enhanced the shoot P content of jarrah plants growing under P-deficient conditions. In addition, S. calospora, A. occidentalis, and Scleroderma sp. all stimulated plant growth significantly. All inoculated plants had significantly lower phytotoxicity symptoms compared to NM controls 7 days after addition of an elevated P dose (30 mg P kg(-1) soil). Following exposure to toxicity-inducing levels of P, the shoot P concentration was significantly lower in R. irregularis-inoculated and dually inoculated plants compared to NM controls. Although all inoculated plants had reduced toxicity symptoms and there was a positive linear relationship between rank and shoot P concentration, the protective effect was not necessarily explained by the type of fungal association or the extent of mycorrhizal colonization.
authors.affiliation: School of Earth and Environment M087, The University of Western Australia, Crawley, WA, 6009, Australia.
authors.forename: Khalil
authors.initials: K
authors.lastname: Kariman
authors.forename: Susan J
authors.initials: SJ
authors.lastname: Barker
authors.forename: Patrick M
authors.initials: PM
authors.lastname: Finnegan
authors.forename: Mark
authors.initials: M
authors.lastname: Tibbett
mesh_terms: D004361:Drug Tolerance; D005052:Eucalyptus / Q000737:chemistry / Q000187:drug effects* / Q000382:microbiology* / Q000502:physiology; D038821:Mycorrhizae / Q000254:growth & development / Q000378:metabolism / Q000502:physiology*; D010758:Phosphorus / Q000378:metabolism* / Q000633:toxicity*; D063245:Plant Development / Q000187:drug effects; D010935:Plant Diseases / Q000139:chemically induced / Q000517:prevention & control; D018520:Plant Shoots / Q000737:chemistry / Q000187:drug effects / Q000382:microbiology / Q000502:physiology; D036226:Seedlings / Q000737:chemistry / Q000187:drug effects / Q000382:microbiology / Q000502:physiology; D013559:Symbiosis
chemical_list: D010758:Phosphorus