Pea rust
| Pea rust | ||||||||||||
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Cypress milkweed individuals infected with pea rust ( Uromyces pisi ) |
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| Systematics | ||||||||||||
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| Scientific name | ||||||||||||
| Uromyces pisi | ||||||||||||
| ( DC ) GH Otth |
The peas rust ( Uromyces pisi ) is a stand fungal art from the order of the rust fungi (Pucciniales). The fungus is an endoparasite of milkweed and butterflies . Symptoms of the infestation by the species are rust spots and pustules on the leaf surfaces of the host plants. It is spread all over the world.
features
Macroscopic features
Uromyces pisi can only be recognized with the naked eye by the spore beds protruding on the surface of the host. They grow in nests that appear as yellowish to brown spots and pustules on the leaf surfaces.
Microscopic features
The mycelium of Uromyces pisi grows as with all Uromyces TYPES intercellular and forms Saugfäden that grow into the storage tissue of the host. The spermogonia of the species growing on the underside of the host leaves are scattered. The aecia growing between them are cup-shaped and white. The aeciospores are usually angular to ellipsoidal, orange, warty and 18–23 × 18–23 µm in size. The uredia of the fungus, mostly growing underneath the leaves, are cinnamon yellow, powdery and uncovered early. Their yellow-brown uredospores are almost spherical to spherical, 15–32 × 14–23 µm in size and warty. The parts of the species growing on both sides of the host leaves are light brown, uncovered early, confluent and powdery. The brown teliospores are unicellular, usually ovoid to almost spherical, smooth and 20–28 × 14–24 µm in size. Their stem is colorless and short.
distribution
The known distribution area of Uromyces pisi includes the entire world.
ecology
The host plants of Uromyces pisi for the Haplont are the milkweed Euphorbia cyparissias and various butterflies for the dikaryote . The fungus feeds on the nutrients present in the storage tissue of the plants, its spore beds later break through the leaf surface and release spores. The species goes through a development cycle with Aecien, Spermogonia, Telien and Uredien and undergoes a host change, but is not dependent on it.
The infestation by Uromyces pisi prevents the milkweed from blooming. The infected plants are immediately recognizable by a deviating habit (yellowish, elongated, with shorter leaves). At the tip of the shoot they form a "pseudo-flower" with a rosette of yellow-colored leaves. The effect of the fungus on the plant extends not only to the coloration but also to the secretion of nectar. Pseudo flowers, just like the real flowers, are visited by insects (albeit a little less often). By experimentally excluding the insects, it was proven that the insect visit plays an essential role in the fertilization of the (heterothallic) fungus.
literature
- Ernst Gäumann: The rust fungi of Central Europe. With special consideration of Switzerland . In: Contributions to the cryptogam flora in Switzerland . tape 12 . Commission publisher Buchdruckerei Büchler & Co, Bern 1959.
Individual evidence
- ↑ Monika Pfunder & Barbara A. Roy (2000): Pollinator-mediated interactions between a pathogenic fungus, Uromyces pisi (Pucciniaceae), and its host plant, Euphorbia cyparissias (Euphorbiaceae). American Journal of Botany vol. 87 no. 1: 48 - 55. online
