With approximately 7000 species belonging to ca. 120 genera rust fungi form the largest group of phytopathogenic fungi world-wide. Although their host spectrum includes economically important plant families like Poaceae, Fabaceae or Asteraceae, the knowledge about the ecology of rust fungi, their distribution and their influence on vegetation is very poor. In the pilot phase of BIOTA-Africa, the principle aim of subprojekt S03b was to collect rust fungi in south-western Africa where hardly any rusts had been encountered hitherto. In the frame of this work, 63 rust species could be found in Namibia and 49 species in the western part of South Africa, of which 19 are new to science. Descriptions of the new species and a preliminary flora of rust fungi of Nambia are just being published.

In the main phase, the data gathered in the pilot phase will be supplemented by additional field work and by data from literature and herbaria. The entire information will be stored in a database ("SAfri-rust") that has already been established. The database will provide data on rust taxonomy, host range, geographical distribution and morphological characters and thus will be applicable as an identification tool for rust fungi as well as a source of information on this important group of parasites. Another aim of S03b is to discover patterns of the occurrence of rust fungi in the biomes of south-western Africa and to interpret the observed findings. The "SAfri-rust" database will enable us to find such patterns of rust fungus distribution, to analyse the dependency of the rust mycota from different vegetation types, and to look for interrelationships between morphological traits of rust fungi and environmental factors