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Biology of FUNgi

Lecture 11Basidiomycetes II

A look back...

• Agaricus bisporus commercial growing.

• Basidiospore production and release.

• Different types of basidiomycetes.

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• Basidiomycetes do a great number of things.They do also have a great variety of means toget their spores “out there.”

The typical basidiomycete bearsits spores on the gills of a cap;Amanita sp.

Tremella - a jelly fungus - on aStereum - a conk or a polypore

Auricularia auricula anotherbasidiomycetous jelly fungus

Basidiomycete Macrofungi

• Basidiomycetes do a great number of things.They do also have a great variety of means toget their spores “out there.”

Geastrum - an earth star - is acommon puff ball - also amember of Gasteromycetes

Calvatia gigantea - an appropriatelynamed Gasteromycete

Nidulariales - the bird nest fungi - arealso members of Gasteromycetes

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They can form mutualistic symbioticassociations such as mycorrhizae, or live assaprobes on wood, soil, leaves, or dung.

Galerina autumnalis - asaprotrophic agaric

Russula amoenolens - abrittle mushroom - and itsmycorrhizae

Basidiomycete Macrofungi

There are also lichenized agarics,Omphallina umbellifera being agood example of this.

Lichenized fungi are mainlyascomycetous - apothecial,perithecial, ascostromatal. Takentogether this implies that the lichensymbiosis must be a very successfulsymbiosis.

Omphallina umbellifera - alichenized agaric

Basidiomycete Macrofungi

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Meisporic vs. mitosporic reproduction

Asexual reproduction may be of lesserimportance in basidiomycetes than it is inascomycetes (rusts and smuts are anexception to this rule).

Nonetheless, budding and mycelialfragmentation occur.

Some species may produce arthroconidia,which basically are hyphae fragmented intounicellular propagules.

Examples of arthroconidia production

Basidiomycete Macrofungi

The clamp connections bring us to theissue of life cycle as well as primary,secondary and tertiary mycelia. Althoughvegetative fragmentation is common,mitospores are fairly infrequent among thebasidiomycetes

Haplophase or primarymycelium

Spore germination

Anastomosis of compatiblemycelia. Compatible matingtypes

Vegetative dikaryophaseor secondary mycelium

Organized specializedtissues in the basidiocarp– tertiary mycelium

Basidiomycete Macrofungi

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Fungus of the day -Puccinia graminis

Taxonomy: Phylum (subphylum) Basidiomycota Order - Uredinales Family - Puccinaceae Common names - wheat rust

A teliomycete, a basidiomycete with teliospores.

Puccinia is the largest genus within Uredinales

Economically important - wheat rust

Alternating hosts

Puccinia graminis telial sori onwheat leaf - primary host.Karyogamy occurs somewhere inthe teliospores.

Puccinia graminis pigmented teliosporesdivided to two cells by a transverseseptum. At time of germination, thenuclei go through meiosis.

Fungus of the day -Puccinia graminis

Primary host is the one with the uredinial andtelial(!) stages, i.e., the stage which producesbasidiospores.

No basidiocarps, but germinating teliosporegives rise to the basidia and basidiospores.

Alternate host bears the spermogonia and aecia.Puccinia graminis telial(n+n) sori on wheat.

Puccinia graminis uredinia (n+n)on wheat.

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Fungus of the day -Puccinia graminis

Puccinia graminis is a typicalmacrocyclic rust (possessing all 5stages). 5 stages possible for a heteroeciousrust (fungus with two hosts; primaryand alternate, autoecious are those withonly one host).

Barberry is the alternatehost for Puccinia graminis.

Puccinia graminis spermogonia(n) and aecia (n+n) are formed onbarberry.

Fungus of the day -Puccinia graminis (See Carlile p. 68)

Aeciospores germinate only on primary host andestablish the uredinia (n+n) with urediniospores(n+n). Uredinial stage can repeat itself severaltimes over growing season.

Germinatingbasidiospores (n)establish spermogonia

On alternate host - barberry

On primary host -wheat

Spermatia (n) and receptivehyphae (n) fuse and give rise toaecia (n+n) with aeciospores(n+n)

Urediniosporesultimately establishtelia (n+n) withteliospores (n+n =>2n)

Germinating teliosporesproduce basidia andbasidiospores (n)

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A look forward...

• Heterobasidiomycetes. Rusts like Pucciniaand smuts like Ustillago.

• Biologic control of an Uredinalean plantpathogen.

Holo vs. heterobasidiomycetes

Remember the difference between holo- andheterobasidiomycetes?

Rust teliosporeand promyceliumSmut teliospore

and promycelium

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Smuts and rusts appear more primitive than the basidiomycetous macromycetes(the Hymenomycetes or Tremellales).

Basidiomycetes - telial vs. other basidiomycetes

Primitivebasidiomycetes -Teliosporicbasidiomycetes

Smuts

Rusts

Basidiomycetous macromycetes

Uredinales -Rust fungi

Significance and occurrence of Uredinales

Many of the rusts ubiquitous wherever their hostsare.

Rusts are obligate biotrophs and rarely kill theirhosts.

They cannot survive saprobically. This complicatesstudying them as many, not all, of them fail to growin pure culture.

The greatest puzzle of them all is how can aheteroecious fungal parasite be so successful.

Mayapple rust is an example ofautoecious rust - a rust whichcompletes its whole life cycle in asingle host

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Uredinales -Rust fungi

Significance and occurrence of Uredinales

Rusts maybe the most important basidiomyceteseconomically speaking.

Rusts can cause tremendous losses to manycultivated crops and forest trees. Wheat and whitepine as examples.

Cronartium ribicola blister rust of whitepines. Blisters are aecia on the pine stem.Species was introduced to western NA fromFrance in late 1800s: great losses in theeconomically important pines.Primary hosts are gooseberries and currants(Ribes spp.)

Uredinales -Rust fungi

Biocontrol of C. ribicola

Cronartium ribicola serves beautifully as an exampleof a non-fungicidal pathogen control. White pine blisterrust has been controlled with Ribes spp. eradicationprogram; with some success.Biocontrol failed with Puccinia graminis: removal ofthe secondary host - barberry - not enough.For example, in Mexico, wheat is produced year aroundand wheat leaf rust gets about by its urediniosporesalone.The uredinospores travel to Kansas and establish newepidemics. This gives you some appreciation on thedistance of dispersal.

Cronartium ribicola blister rust of whitepines. Blisters are aecia on the pine stem.

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Smuts and rusts appear more primitive than the basidiomycetous macromycetes(the Hymenomycetes or Tremellales).

Basidiomycetes - the other telial basidiomycetes -smuts (Ustillaginales)

Primitive basidiomycetes

Smuts

Rusts

Basidiomycetous macromycetes

Ustillaginales - the smut fungi

• Like the rusts (Uredinales), smuts areteliomycetes, i.e. basidiomycetes whichproduce basidia from teliospores.

• The term smut refers to the black sootymasses of teliospores on the diseased plants.

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Life just cannot get much better. We have just lookedinto rusts and now, the smuts.

The corn smut - Ustillago maydis.

Although corn smut can spoil crops of sweet corn, theend result is edible. Called ‘cuitlacoche’ or maizemushroom in Mexico is a great delicacy.

Inoculation programs are being tested to study ifmethods for larger numbers of unsightly galls couldbe created for sale.

Ustillago maydis occurs pretty muchwherever corn occurs.

Ustillaginales - the smut fungi

Ustillaginales -smut fungi

Significance of the smuts

Economically, smuts parallel rusts inimportance. They colonize cereal grains andcause millions of dollars worth of damage tocrops. Ornamentals can be affected as well.Some smuts (e.g. Tilletia triciti of wheat) canhave an offensive odor (trimethylalanines)causing a smell like rotting fish. For somereason the grain is considered unfit for humanconsumption.

In addition to corn colonizing smut,Ustillago maydis, many cereal grains arealso infected by smuts. Ustillago nuda asan example.

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Ustillaginales -smut fungi

Significance of the smuts

Clearly, spoiling foods is a major concern.

The smut spores can also cause a hazard tothose working with infected grains.

• First, the spores are known allergens.

• Second, spores can be present in volumeslarge enough to accumulate in machinery andcombust.

Machinery combusting becauseof smut spores is not to beconfused with SHC, unless...

Ustillaginales -smut fungi

Smut’s life

Smut fungi and rusts are similar in manyrespects. Both being teliomycetes, they gothrough karyogamy in the teliospore. Oncethe teliospore germinates, it produces thepromycelium, basidia andbasidiospores.

Germinating teliosporeproduces promycelium, whichgives rise to basidiospores.

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Ustillaginales -smut fungi

Smut’s life

Some important differences exist, too.Once the basidiospores germinate, theycan go about their life as free-living yeast-like saprobes. In other words themonokaryotic phase can live saprobicallyby budding.

In many ways the life is just much moresimple as smut fungus.

Ustillaginales -smut fungi

Smut’s life

In brief, smut fungi colonize their hosts asdikaryon after plasmogamy of twohomokaryons. This mycelial dikaryon willproduce sori with teliospores. The soriappear as long black streaks on the hostsurfaces.

The dikaryotic myceliumproduces binuceate teliospores.The great volumes of theteliospores earn the name smutfungi for Ustillaginales.

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Summary

This is the level of phylogenetic resolutionwe will settle for now.

Keep in mind how the different groups ofbasidiomycetes are related to each other.

Smuts and rusts may possibly be theeconomically most importantbasidiomycetes.

Although the smuts and rusts rarely, if ever, kill their hosts, they certainly can doa lot of damage by spoiling the food stuffs.