Symbionts, mutualists, parasites: Symbionts, mutualists, parasites: Plant-fungus relationships amongst the Plant-fungus relationships amongst the

mycorrhizae and endophytesmycorrhizae and endophytes

Relationships between plants Relationships between plants and fungiand fungi

Symbionts (Symbionts (e.g.e.g. mycorrhizae) mycorrhizae)

EndophytesEndophytes

Parasites and pathogensParasites and pathogens

Ecto- Ecto- vsvs Endo- Endo-mycorrhizaemycorrhizae

2,000 species of plants -- mainly trees 18 families

Gymnosperms:  ALL Pinaceae

Angiosperms: ALL Fagaceae (beech),

Betulaceae (birch), Salicaceae (willow), Dipterocarpoideae (lauan)

MOST Myrtaceae (eucalypt) MANY legumesSOME Aceraceae

Euphorbiaceae, RosaceaeTiliaceaeUlmaceae7 other families

>300,000 species of plants -- both herbaceous and woody

380 families

NOT endomycorrhizal manyALL Brassicaceae

Commelinaceae (Tradescantia), Juncaceae (rush)Cyperaceaee (sedge)Proteaceae, 

SOME Amaranthaceae (Celosia), Caryophyllaceae (carnations), Chenopodiaceae (spinach), Polygonaceae (buckwheat), members of 3 other families

MOST ectomycorrhizal spp.

Overall, >95% plant species are thought to have mycorrhizal associates

Mycorrhizae – predominant Mycorrhizae – predominant formsforms

Direct penetration of tissues and cells

Root cells are surrounded but not invaded

Zygomycete affinities Asco/basidiomycte affinities

Fungi in Rhynie chert, Fungi in Rhynie chert, 400MYa400MYa

Rhynia Rhynia with with PaleomycesPaleomyces

Agalophyton with Glomites Agalophyton with Glomites rhyniensisrhyniensis

General roles of General roles of mycorrhizaemycorrhizae Mycorrhizal plant can Mycorrhizal plant can

exploit several times the exploit several times the volume of soil available to a volume of soil available to a non-mycorrhizal plant non-mycorrhizal plant Environment to plantEnvironment to plant Plant to/from fungusPlant to/from fungus Between plants – ecological Between plants – ecological

integrationintegration Pathogen relationsPathogen relations

Physical protectionPhysical protection AntibioticsAntibiotics Increased plant vigourIncreased plant vigour

Mycorrhizae may alsoMycorrhizae may also

induce antibiotic production by the induce antibiotic production by the plantplant

alter the quantity and quality of root alter the quantity and quality of root exudates exudates affects rhizosphere affects rhizosphere microfloramicroflora

improve host vigor improve host vigor for improved for improved resistanceresistance

Mycorrhizae as ecosystem Mycorrhizae as ecosystem integratorsintegrators

Major types of Major types of mycorrhizaemycorrhizae

EctomycorrhizaeEctomycorrhizae Arbuscular (endomycorrhizae)Arbuscular (endomycorrhizae) EricoidEricoid OrchidoidOrchidoid ArbutoidArbutoid MonotropoidMonotropoid

EctomycorrhizaeEctomycorrhizae Only on actively growing Only on actively growing

(feeder) roots)(feeder) roots) Persistent – months to Persistent – months to

yearsyears Fungal mantle and Fungal mantle and

Hartig netHartig net Typically, fungal Typically, fungal

dikaryomycete symbionts dikaryomycete symbionts do not produce cellulasedo not produce cellulase

BasidiomycetesBasidiomycetes Amanita, Russula, Suillus, Amanita, Russula, Suillus,

PisolithusPisolithus Ascomycetes Ascomycetes

Tuber melanosporiumTuber melanosporium

Root colonization by Root colonization by ectomycorrhizaeectomycorrhizae

Amanita muscaria on Pinus strobus

Heterorhizy plant growth substances produced/induced by fungus

promote/retain juvenile roots promote/retain juvenile roots reduced root hairsprevent wood growthprevent wood growth

Pisolithus tinctoriusPisolithus tinctorius

has been shown to establish mycorrhizas has been shown to establish mycorrhizas with ~ 50 different tree species with ~ 50 different tree species

DJ Lodge

Ascomycete Ascomycete ectomycorrhizaectomycorrhiza

Ascomycetes – Ascomycetes – Tuber melanosporum Tuber melanosporum $2000/kg retail $2000/kg retail freshfresh

Modified apothecium Modified apothecium gleba gleba Mycorrhizal on oak, 125g/tree/year, Mycorrhizal on oak, 125g/tree/year,

full production in 10yrfull production in 10yr Cultivation, 1000 trees/hectare, 3m Cultivation, 1000 trees/hectare, 3m

apartapart Crowded growth leads to faster Crowded growth leads to faster

fruitingfruiting

Arbuscular mycorrhizaeArbuscular mycorrhizae Common especially on Common especially on

herbaceous plants; some herbaceous plants; some trees trees e.g.e.g. sycamore sycamore

Formerly Formerly Zygomycota/GlomalesZygomycota/Glomales now Glomeromycotanow Glomeromycota

Large sorocarps and Large sorocarps and spores produced spores produced adjacent to roots, but adjacent to roots, but subterraneansubterranean

Obligate biotrophs, each Obligate biotrophs, each interaction interaction temporallytemporally limitedlimited days to weeks days to weeks

Penetrates plant roots Penetrates plant roots /cells/cells

AM root colonization AM root colonization patternpattern

Cyclical formation of arbuscules followed by degradation *may form vesicles

Formerly called Formerly called VesicularVesicular Srbuscular mycorrhizaeSrbuscular mycorrhizae

Not all endo-Not all endo-mycorrhizae form mycorrhizae form vesiclesvesicles

May be final stage in May be final stage in limited term limited term symbiosissymbiosis

May be May be characteristic of characteristic of specific plant:fungus specific plant:fungus interactionsinteractions

www.apsnet.org/education/IllustratedGlossary/PhotosE-H/endomycorrhiza.jpg

(Vesicular) arbuscular (Vesicular) arbuscular mycorrhizaemycorrhizae

Spore transport Spore transport may be facilitated may be facilitated by burrowing by burrowing animalsanimals

Diversity is much Diversity is much larger than larger than realized, until realized, until recentlyrecently

Other mycorrhizaze Other mycorrhizaze groupsgroups

Bidartondo and Bruns 2001

Ericoid mycorrhizaeEricoid mycorrhizae Important for nitrogen acquisition in boggy soil Important for nitrogen acquisition in boggy soil

includes invertebrate predationincludes invertebrate predation Colonized by some ascomycetes, e.g. Colonized by some ascomycetes, e.g.

Hymenoscyphus ericaeHymenoscyphus ericae (also forms mycorrhizae with (also forms mycorrhizae with liverworts)liverworts)

loose net over the growing (distinctive) hair rootsloose net over the growing (distinctive) hair roots fungus penetrates cortical cells fungus penetrates cortical cells fills with densely fills with densely

coiled hyphae (not arbuscules)coiled hyphae (not arbuscules)

Ericoid mycorrhizaeEricoid mycorrhizae

Hyphae penetrate roots, but Hyphae penetrate roots, but nevernever enter enter the cellsthe cells

Hartig net Hartig net Plant identification helps understanding Plant identification helps understanding

mycorrhizal relationshipmycorrhizal relationship

www.ffp.csiro.au/research/mycorrhiza/intro/monotropa.jpg

Arbutoid mycorrhizaeArbutoid mycorrhizae• develop on short primary

roots of Arbutus and Pyrola

• mantle of fungal tissue• Hartig net

• differential characteristic: fungi penetrate the walls of root epidermal cells, forming branching hyphal complexes in the cell

fungi that form arbutoid mycorrhizae: ascomycetes and

basidiomycetes that form ectomycorrhizae on other species (such as conifers)

Orchid mycorrhizaeOrchid mycorrhizae Seedling orchid isSeedling orchid is entirely entirely

dependent on mycorrhiza for dependent on mycorrhiza for nutrition months … years nutrition months … years

Achlorophyllous orchidsAchlorophyllous orchids highly fungus specifichighly fungus specific can parasitize ectomycorrhizal can parasitize ectomycorrhizal

fungi (CHO from surrounding fungi (CHO from surrounding trees)trees)

Fungal partners Fungal partners RhizoctoniaRhizoctonia spp; some spp; some

ArmillariaArmillaria root pathogens, including some root pathogens, including some

pathogenic isolatespathogenic isolates Both plant and fungus are Both plant and fungus are

live, but fungus degradeslive, but fungus degrades

Corallorhiza maculataCorallorhiza maculata

Orchidoid mycorrhizae – a Orchidoid mycorrhizae – a balancing actbalancing act

Monotropa Monotropa depends on depends on mycorrhizaemycorrhizae

Arrowhead: penetration peg

Endophytic fungiEndophytic fungi

www.sci.utu.fi/biologia/ekologia/endofyytti.htm

Perennial ryegrassPerennial ryegrass Adapted to a wide range of

soils, including heavy clay and poorly drained soils, but prefers well-drained soils of medium to high fertility. It tolerates soil pH ranging from 4.5 to 8.4

Short-lived, cool-season perennial under western Canadian conditions

Readily crosses with fescue spp, meadow and tall fescue

The fescue mysteryThe fescue mystery

Some fescue has relatively low palatability to Some fescue has relatively low palatability to livestocklivestock

performance of animals grazing it was erratic performance of animals grazing it was erratic and often disappointingly lowand often disappointingly low

cattle grazing fescue occasionally developed cattle grazing fescue occasionally developed lameness and sometimes lost portions of their lameness and sometimes lost portions of their feet or tails during fall and winter feet or tails during fall and winter

mares grazing tall fescue pastures often mares grazing tall fescue pastures often aborted, produced stillborn foals, had aborted, produced stillborn foals, had thickened or retained placentas, or produced thickened or retained placentas, or produced an inadequate quantity of milk an inadequate quantity of milk

Acremonium Acremonium coenophialumcoenophialum

does not affect either the growth or does not affect either the growth or appearance of the grassappearance of the grass

requires a laboratory analysis to requires a laboratory analysis to detect its presencedetect its presence

seed transmitted and apparently not seed transmitted and apparently not transmitted in any other waytransmitted in any other way

Vomitoxin: deoxynivalenol (DON)

mycotoxin produced by several species of Fusarium

scab or head blight in barley, wheat, oats, and rye

Deoxynivalenol T2 toxin

[DON] Permitted in food and feed

1 ppm - wheat products for human consumption.

5 ppm - Grain and grain byproducts destined for swine and other animal species (except cattle and chickens) not to exceed 20 percent of the diet for swine, not to exceed 40 percent for other animal species.

10 ppm - Grain and grain byproducts for ruminating beef and feedlot cattle older than 4 months and for chickens not to exceed 50 percent of the diet.