Mycology (Bio 594, Special Topics)M. Marshall, 2013Shippensburg University(See last slide for additional credits)

Ustilaginomycetes, The Smut fungi

Agaricomycotina Mushrooms, puffballs, shelf fungi, jelly fungiUstilaginomycotina Smut fungi and allied taxaPucciniomycotina Rust fungi and allied taxa

Begerow et al. 2006. Mycologia 98: 906-916

Subphylum Ustilaginomycotina• 1500 species, 80 genera

• Mostly plant pathogenic fungi (biotrophs)– Infect > 4000 species of plants in 75 families of

angiosperms

• Group united by:– Sequence analysis of large subunit rDNA– Host/parasite zone of interaction– Septal pores lacking parenthesomes, but some with

dolipore– Parasitic dikaryotic phase and saprotrophic haploid phase• Many taxa dimorphic, with yeast-like haploid phase

and mycelial dikaryotic phase

Interaction zones and septal pores in Ustilaginomycetes. From Bauer et al. 2001. The Mycota VII. Part B. Chapter 3.

• Ustilaginomycetes– Ustilaginales – Urocystales

• Exobasidiomycetes (we won’t cover)– Tilletiales– Malasseziales– Exobasidiales– Georgefischeriales– Entylomatales– Doassansiales– Microstomatales

• Entorrhizomycetes– Entorrhizales

The Smut Fungi

• “Smut” term comes from the dark masses of teliospores formed by many members of the group

Smut Fungi

• Economically important pathogens include:– Ustilago maydis (corn smut)– Tilletia controversa (dwarf bunt of wheat)– Tillieta tritici and T. laevis (common bunt)– Tilletia indica (Karnal bunt of wheat)– Urocystis agropyri (flag smut)

From Casselton and Olesnicky, 1998

Mating Systems in Smut Fungi• Heterothallic/tetrapolar (e.g., Ustilago maydis)– Two unlinked mating type (MAT) loci a and b• a locus

– 2 alleles: a1 and a2– Includes pheromone and pheromone receptor genes that

control cell-to-cell signaling– controls fusion of haploid cells to form dikaryon

• b locus – multiple alleles (25 in U. maydis)– regulates filamentous growth of dikaryon – is a main determinant of pathogenicity

• Heterothallic/bipolar (e.g., Ustilago hordei)– a and b loci are physically linked on one chromosome

Teliospore germination

Basidiospores

Basidium

Ustilago-type Tilletia-type

Basidial types in. From Bauer et al. 2001. The Mycota VII. Part B. Chapter 3. Ustilaginomycetes

Dikaryon formation

• Conjugation of primary or secondary basidiospores

• Conjugation of basidium cells

H-body

Secondary Basidiospores (Tilletia)

Forcibly discharged, formed from sterigma-like structure

Passively dispersed

Sorus (pl. sori)

• Teliospores are formed in sori• Composed of host and fungal tissues• Formed in host ovaries, stems, leaves, or roots

depending on the smut taxon• Characters of taxonomic importance include:– Thread-like structures (fungal)– Sterile cells– Columella (host)– Peridium (host or fungus)

• Persistent = covered smut• Thin, breaking down to expose spores = loose smut

Teliospores

• Formed singly or in spore balls• Mostly globose, pigmented, with thick,

ornamented walls• Size ranges from 3.5 to 60 µm diam• Resistant structures, in some species can

survive up to 10 years in soil, and 25 years or more under optimal conditions

Teliospores

Smut Diseases

• Based on location of sorus in host:– Inflorescence smuts– Leaf smuts– Stem smuts– Root smuts

Common types of smut diseases

• Bunt– Ovary-infecting species

of Tilletia that infect cereals

• Stinking Bunt– Diseases caused by

Tilletia species that produce foetid (fishy) odor

Common types of smut diseases

• Partial Bunt– Only a portion of seed or

inflorescences are bunted, only part of seed is replaced by sorus

Karnal bunt (Tilletia indica)Tilletia walkeri infecting Lolium multiflorum

Ustilago

• Sori in reproductive organs or vegetative tissues of host

• Teliospores formed singly, usually pigmented with sculptured walls

• Sterile cells absent• Ustilago-type

germination

Common types of smut diseases

• Covered smut – Well-developed,

persistent peridium surrounding sorus

• Loose smut– Thin, delicate

peridium that ruptures easily to expose teliospores

Tilletia• Sori usually in reproductive

organs of host• Teliospores formed singly,

usually pigmented with ornamented walls

• Sterile cells present in sorus• Teliospores with foetid odor

due to production of trimethylamine

• Tilletia-type germination

Corn Smut, Ustilago maydis

Loose Smut of Wheat, Ustilago nuda, and U. tritici

Covered Smut of wheat, Telletia carries, T. foetida.

Smut “groups”- Overall Chart

This outline is just provided as a convenience for study purposes - Obtained from Pl. Path. Dept., U. of Nebraska

Smut groups

sheet A

Smut Groups sheet B

Ignore the remainder

Entyloma

• Sori in vegetative organs of host

• Teliospores formed singly, permanently embedded in host tissue

• Teliospores with pale, smooth walls

• Tilletia-type germination

Urocystis

• Sori mostly in leaves, stems, forming streaks, swellings or galls

• Spore balls with pigmented teliospores surrounded by hyaline sterile cells

• Tilletia-type germination

Thecaphora• Sori in various parts of host,

mostly reproductive organs• Spore balls comprising

several to many, pigmented, wedge-shaped teliospores with sculptured outer walls

• Germination by formation of septate metabasidium, cells form hyphae that fuse to establish dikaryon

http://www.redepapa.org/thecaphora.jpg

Order Exobasidiales

• Plant parasitic fungi• Form holobasidia on leaves, no teliospores

formed• Basidiospores become septate during

germination• Dimorphic• Four families, two will be covered:– Exobasidiaceae– Graphioloceae

Exobasidiaceae: Exobasidium

Graphiola

Credits

This presentation has been modified from one posted on the web by Dr. Lori Carris, Washigton State University Plant Pathology Dept. from her course: Plant Path 521, Mycology.