Fungi

At first sight, most people will associate fungi with a tasty meal as numerous mushrooms are very delicious and common components in our kitchen. Well-known are also, although rather inconspicuous, fungi like brewer’s yeast and blue mould of cheese which we use (industrially) for the production or refinement of food and luxury food. Antibiotic producing moulds are among the useful fungi as well. We dread other fungi, such as the life threatening poisonous Death Cap, moulds on the wall or the Dry Rot Fungus in a cellar vault. Apart from this, fungi often pass unnoticed in contrast to plants, being omnipresent, or animals. This is astonishing. Finally, the so-called true fungi, to which most fungal species belong, form their own kingdom (Regnum Fungi) with high diversity. With an estimated 1.5 million species the fungi outnumber the vascular plants by a factor of five to six. In this context it should be emphasized that fungi are not related to plants (Regnum Plantae) but they form a sister group with animals (Regnum Animalia). Fungi are potentially immortal and they form the tallest individuals. The honey mushroom, often classified

as the tallest organism on earth by the popular press, can form a mycelium of several km2. The inconspicuous nature of fungi may be explained by their short-lived and erratically formed fruitbodies, the only part of the fungus that we see. The major part of the fungal biomass consists of invisible hyphae (in a body called mycelium) in the substrate such as soil, wood, litter, horn, or living tissue of hosts. Hyphae release enzymes into the substrate and after decomposition take up smaller soluble components by endocytosis and thus gain their energy for growth and reproduction.

This external digestion is different from the internal digestion (ingestion) of most animals and the autotrophic life style of plants. There are three basic types of nutrition in fungi: As saprobes they decompose dead organic material and mineralize it. Without fungal saprobes life on our planet would not be possible, because other organisms would suffocate in the organic “waste”. As symbionts (mycorrhizal and lichenized species) they supply plants or algae with water and minerals and promote their growth. Finally, there are many parasites of plants and animals. Their significance among other things as regulator and promoter of evolutionary processes is immense. Many people view this differently, the more so as many parasites are pests of cultivated plants reducing crop yields and misshape ornamental plants. Research emphasis in mycology at the Natural History Museum is this last-named group. More precise: Obligate plant parasitic microfungi such as rust fungi (Pucciniales) and Powdery mildews (Erysiphales). These fungi are very small, host-specific and often have complicated life cycles. Subject of research and scientific projects is their taxonomy, ecology and floristics.

 

Taxonomy

Taxonomic studies were carried out exclusively with rust fungi in several projects (Projects).

Rust fungi (Pucciniales oder Uredinales) are obligate plant parasitic microfungi with appr. 8.000 known species. Hosts are vascular plants and most species have a narrow host range. Many species have complicated life cycles with several spore states and up to seven morphologically different spore types. The name “rust fungus” traces back to one spore type, the urediniospores and their sori (uredinia) which are often rust coloured. Among rust fungi there are many important pathogens of cultivated plants, such as cereal rusts (e.g. the black stem rust Puccinia graminis). Very special are host-alternating species with two hosts, an aecial and a telial host.  This phenomenon is called heteroecity in rust fungi and is widespread among northern hemisphere species. Tranzschelia pruni-spinosae, e.g., switches from Aemone ranunculoides  (Ranunculaceae) with spore states 0 and I to  Prunus spinosa (Rosaceae) with spore states II, III and IV.

Many species are still not known to science and species delimitation is often difficult. Therefore classical methods (light and scanning electron microscopy) are combined with sequencing  rDNA within the framework of our studies. Both, fresh and herbarium material are used for DNA extraction.

 

Rustologist and his favourite locality
Rustologist and his favourite locality
The rust fungus Coleosporium plumeriae, Hawaii
The rust fungus Coleosporium plumeriae, Hawaii
Host-alternating Puccinia alnetorum deforming its aecial host Clematis
Host-alternating Puccinia alnetorum deforming its aecial host Clematis