Smuts and Rusts

Ustilaginomycotina

The Smuts

Pucciniomycotina

The Rusts

Basidiomycota Characteristics

• basidium

• dolipore septae

• clamp connections

• possible rhizomorphs

Agaricomycetes

Have a hymenium

Ustilago maydis

corn smut

Characteristics of smuts

• parasites in fungi and angiosperms

• produce sori- formation of galls

• simpler life cycles

• usually, mycelium remains in a specific tissue (flowering parts)

• most are basically growth-altering parasites that cause necrosis of the host tissue just before sporulation

Galls

Abnormal growth of plant tissues on any part of the plant, localized

Ustilago tritici

loose smut of wheat

Tilletia caries

Common bunt of wheat

Tilletia life cycle

• spores are borne sessile, no sterigmata

• meisosis occurs either in germinating teliospore or in the promycleium that emerges from the teliospore

• basidiospores are borne either one per cell or in a whorl

• sporidia- asexual cells that spread the disease-buds

• herterothallic

• dikaryon can’t be cultured

Obligately biotrophic

Must grow on top of a plant, use haustoria

Spermagonia (0)- Plasmogamy Stage

• Female receptive structures

• establishes the dikaryon (n+n)

• when on leaf, usally the upper surface

• usually flask shaped

• all spermatia and receptive hyphae will be be the same sexual type in one spermagonium

Pycnidium

Spermagonium

Aecia (I)- Transfer stage

• transfer from secondary host to primary host

• associated with a spermatium, when on a leaf, usually on the lower side

• germinate to a dikaryon

• consider the transfer stage, which can only infect the primary host tissue

Uredinium (II)- Repeating stage

• a sorus that erupts through the host epidermis

• one celled spore- rust colored

• borne on a stalk

• spores usually infect through the stomata

Telia (III)- Resting stage

• germinates into basidium

• telial horns

Basidium (IV)- Initiation stage

• haploid spores

• initiation stage

• reinfect host and spermatia are produced

• usually penetrate directly by appressorium

Macrocyclic

all 5 spore stages

Microcyclic

some stages are missing

Autoecious

all stages on one host

Heteroecious

two hosts

Primary host

Forms dikaryotic and diploid phases (2,3,4)

Alternate host

Haploid phase occurs here (0), followed by plasmogamy phase (1)