Ectomycorrhizae Mycorrhiza: a symbiotic, non pathogenic, relationship between a fungus and a plant root. mycorrhizae, mycorrhizas Estimated that >85% of terrestrial plants are mycorrhizal First observed by Frank, 1895, on roots of European forest tree species Two main types: ectotrophic (ecto)mycorrhizae in which a sheath of fungal hyphae forms around the cells of the root, from which fungal hyphae extend out into the soil and inwards between root cortex cells. endotrophic (endo)mycorrhizae in which hyphae enter the cortical cells of the root and are enveloped by the plasmalemma of the host. Arbuscular mycorrhizae, formed only by Glomeromycotan (Glomalean) fungi is a type of endo-mycorrhiza, and is the most widely distributed in the plant kingdom and geographically. mycorrhiza: fungus root • form in and on actively growing fine roots • composed of both fungus and plant tissue • mantle – a mass of hyphae that surround the root plantbio.berkeley.edu/~bruns/ plantbio.berkeley.edu/~bruns/ • extramatrical hyphae - hyphae that extend into the soil from the mantle http://www.ffp.csiro.au/research/mycorrhiza/intro.html plantbio.berkeley.edu/~bruns/ Arbuscular mycorrhizae, endotrophic mycorrhizae All Glomalean (Glomeromycotan) fungi Most abundant type, many angiosperm hosts and some Cupressaceae Ectomycorrhizal Hymenomycetes Tremellales Trichosporonales Filobasidiales Cystofilobasidiales Dacrymycetales Auriculariales Gomphoid-phalloid Cantharelloid ectomycorrhizal fungi Hymenochaetoid Russuloid Thelephoroid Polyporoid Bolete Euagarics Multiple evolutionary origins of EcM in Agaricales EcM evolved independently multiple times, derived in lineages with predominantly other ecologies The diversity of structures and species of fungal and plant symbionts indicates that this type of association has evolved independently multiple times, i.e. is polyphyletic. Mycorrhizae, like plant parasitism/pathogenicity, seems to be a life history strategy that fungi are highly predisposed to adopt. Salix, Alnus, Myrica, Rosaceae may have both ecto- and arbuscular mycorrhizae Distribution of mycorrhizas among angiosperms 18% do not have mycorrhizae 50% reported to have VAM 12% reported to have VAM in some cases, but not in others 20% have another type of association (ECM, orchid, ericoid, etc.) Ectomycorrhizal (EcM) Symbiosis diversity: • ~8,000 spp. of plants Betulaceae, Dipterocarpaceae, Fagaceae , Myrtaceae, Pinaceae, Salicaceae some Cupressaceae some Aceraceae, Euphorbiaceae, Fabaceae, Myrtaceae Rosaceae, Ulmaceae most have northern temperate zone distribution, fewer tropical and southern hemisphere Estimated as many as • 7,000~10,000 spp. of fungi form EcM symbioses • Ascomycota and Basidiomycota Ectomycorrhizal Hymenomycetes Cantherellus Ramaria Boletus Tricholoma Ectomycorrhizal Hymenomycetes Rhizopogon Amanita Suillus Russula Laccaria Pisolithus Cortinarius Mycorrhizae: benefits to host plant • Increase the surface area of plant-soil interface • Increase nutrient supply by enabling plants to access nutrients otherwise unavailable, e.g. insoluble forms of P • Protect roots from infection by pathogenic fungi, nematodes • Increase plant fitness through increased vigor, reproduction • Transfer of carbon, nutrients within and between plant species through common mycorrhizal networks Fungal benefits • sugars: est. that trees invest 10% of total photosynthates to their mycobionts • sugars that are transported from the plant to the fungus are converted into trehalose, mannitol & glycogen not available for resorption by the plant--one-way transfer • spore germination factors, root exudates Plant benefits • increased uptake surface area, better expoitation of soil • phosphorus, calcium, potassium, copper, molybdenum, magnesium, zinc, nitrogen • water • protection against root pathogens, grazers Current classification of mycorrhizae types Ectomycorrhizae (ECM)—various hymenomycetes, and a few ascomycetes, about 5% of all mycorrhizal associations Pinaceae, Fagaceae, Betulaceae, Myrtaceae About 2,000 plant spp Plant cells not penetrated by fungal hyphae Arbuscular (AM, VAM)—Glomeromycota 300,000+ spp. of plants non-mycorrhizal plants found in Brassicaceae, Chenopodiaceae, Commelinaceae, Cyperaceae, Caryophyllaceae, Amarathaceae, Juncaceae, a few others plant cells penetrated, arbuscules Ectomycorrhizae Fine hyphae enable plants to more thoroughly penetrate the soil, extract nutrients Ectomycorrhizae hartig net: growth of hyphae in between and around cortex cells in Gymnosperms http://www.ffp.csiro.au/research/mycorrhiza/intro.html and epidermal cells in Angiosperms http://www.ffp.csiro.au/research/mycorrhiza/intro.html hyphae do not penetrate cells of cortex; site of nutrient transfer Current classification of mycorrhizae types Ericoid – fungi mainly asco- but a few basidiomycete fungi, plant hosts are Ericaceae (Erica, Rhododendron, Vaccinium, Gaultheria), occupy low nutrient soils • Hymenoscyphus (asco), Clavaria (basid) • Ericaceae hosts Rhododendron, Calluna, Vaccinium, Gaultheria • Very fine roots, 2-3 cell layers thin; “hair roots” • No epidermis, no root hairs • Loose covering layer of hyphae, not like mantle • Surronding layer of fungal hyphae, penetrates cortex cells, form coiled structures (pelotons) • also leafy liverworts have similar colonization by Hymenoscyphus (ascomycete) Ericoid mycorrhizae Current classification of mycorrhizae types Arbutoid—ascomycete and basidiomycete fungi, Arctostaphylos, Arbutus hosts • Fungi that form ectomycorrhizae with other hosts – e.g. Cortinarius, Lactarius also form ECM with other plant spp. • Like typical ectomycorrhizae, except root cortical cells are penetrated like ericoid mycorrhizae • coiled structures (pelotons) Monotropoid -- mycotrophic plants parasitic on ectomycorrhizal fungi, Monotropa, Allotropa • Fungal partners all basidiomycetes, e.g. Tricholoma magnivelare (Matsutake), Russula, Rhizopogon • Roots covered by a mantle, simple peg-like structure surrounded by plant plasmalemma • Tip of peg lysed by plant, fungal cell contents absorbed Arbutoid Arbutoid mycorrhizae Monotropoid mycorrhizae Current classification of mycorrhizae types Orchids—obligately mycotrophic (mycoparasitic) plants • about 100 spp of fully mycotrophic orchids • 30,000 spp of orchid initially mycotrophic before leaves develop • fungal partner spp. of “Rhizoctonia”, a polyphyletic genus. Rhizoctonia species occur in Ceratobasidiales, Tulasnellales, Sebacinales Most “Rhizoctonia” are plant pathogens or saprobes, but those that are exploited by fully mycoparasitic orchids are ectomycorrhizal with trees .