Rusts and Smuts Basidiomycota Most economically important group of fungi in Basidiomycota. Class: Uredinomycetes (Rusts) Basidiocarp absent. Class: Ustomycetes (Smuts) Basidium and basidiospores borne from germinating teliospore. Basidia and basidiospores

Teliospore

Rusts and Smuts Class: Uredinomycetes Only Basidiomycota with sexual organs. Septa simple, without dolipore septum. All members obligate parasites. Life cycle differs from Basidiomycetes. Most complex life cycles of all organisms. Parasitic. With at least two and up to five spore stages. Puccinia graminis (Wheat Rust) used as representative life cycle: Macrocyclic: has five spore stages. Heteroeciouis: requires two hosts to complete its life cycle.

Spore Stages of Puccinia graminis Puccinia graminis Life Cycle Summary Stage 0: Spermogonium also referred to as a Pycnium. Produces spermatia and receptive hyphae. Stage 1:Aecium produce aeciospores. Stage 2:Uredium produce urediospores. Stage 3:Telium produce teliospores. Stage 4:Basidium produce basidiospores.

1 Uredium and Urediospores Uredium and Urediospores Begin life cycle, in early spring, with Prepared slide of uredium and binucleate urediospore stage. urediospores. Urediospores reinfect wheat

Telium and Teliospores Telium and Teliospores In late summer, Uredium converts to Telium, which produces binucleate teliospores. Overwinters in teliospore stage Karyogamy occurs in teliospore. Prepared slide of two-celled teliospore stage.

Basidium and Basidiospores Basidium and Basidiospores Basidium and basidiospores borne from germinating teliospore

Karyogamy and meiosis occurs in teliospore. Teliospore germinates to form basidium and Basidiospore basidiospores. Basidiospore infects Barberry (alternate Teliospore host)! Basidium

2 Spermogonium Spermogonium Basidiospores germinate to form monokaryon. Spermogonium with spermatia and receptive hyphae produced.

Spermogonium Spermogonium and Aecium Spermatium of A1 must fuse with Prepared slide of Spermogonium and receptive hyphae of A2 mating strain Aecium. and vise versa Flies carry spermatia to receptive Spermogonium: hyphae. Attracted to spermogonium Receptive by sweet exudates hyphae and Dikaryon reformed below Spermatia spermogonium to form aecium on lower surface of barberry leaves. Aecium and aeciospores

Aecium and Aeciospores Aecium and Aeciospores Aeciospore must now infect wheat to complete lifecycle. Prepared slide of aecium and aeciospores Aeciospores held together by disjunctors

3 Variations in Spore Stages Class: Uredinomycetes

Demicyclic: Rust is missing uredium Variations in stage. teliospore Microcyclic: Rust is missing uredium morphology on and aecium stages. right. Rust can complete entire life cycle on one host: autoecious. Teliospore is most variable in morphology and is utilized in defining genera.

Teliospore Variations Teliospore Variations

Phragmidium Puccinia teliospores coronata commonly called “crown rust” because of the horns on the teliospore.

Teliospore Variations Native Rusts

Gymnosporangium Atelocauda libocedri has digitata: Close-up gelatinous of infected teliospores. phyllodes with spermogonial and aecial stages.

4 Native Rusts Class: Ustomycetes Commonly called smut fungi because Endoraecium teliospores give plant a black, sooty hawaiiense: A appearance. species of native Parasitic on flowering plants. Hawaiian koa rust. Many are dimorphic: Mycelial stage is obligate parasite. Yeast stage is saprobic.

Class: Ustomycetes Class: Ustomycetes In some ways similar to rusts, but also very different: Will use Ustilago maydis (Corn Smut) Fewer spore stages: Only life cycle as representative of smuts. basidiospore and teliospore stage Species dimorphic and parasitic on present. corn. Only one host is required to Fungus replaces kernel with large complete life cycle. sorus of teliospores. Sex organs are absent!

Class: Ustomycetes Ustilago maydis Life Cycle Young sorus filled with dikaryotic mycelium Ustilago maydis: Smut sori filled Square, septate with teliospores. hyphal cells. Ð Hyphal cells rounding off. Ð Globose, thick- walled telispores.

5 Ustilago maydis Life Cycle Ustilago maydis Life Cycle Teliospore germinating to Compatible yeast produce cells basidium and fusion,followed by basidiospores. formation of Basidiospores dikaryon (arrow). “bud” produce yeast. Dikaryon obligate Yeast stage parasite. saprobic

Teliospore Variations Typical Host Appearance

As in rust fungi, Ustilago teliospores cynodontis, variable. bermuda grass smut. Common in Used in defining Hawai‘i. species.

6