Gymnosporangium przewalskii Y.M. Liang & B. Cao
Rust fungi are parasitic fungi that are biotrophic (need their host to stay alive) and produce rust-coloured spores on many different types of host plants. They often have two different plant hosts, spending the first part of their annual life cycle on one plant species and the remainder on another species.
Some rust fungi cause economic loss when infecting agricultural or forestry crops. Gymnosporangium species infect members of the apple subfamily (Amygdaloideae), forming small horn-like sporocarps on leaves; followed by the cypress family (Cupressaceae), on which they form much larger, orange masses of thicker-walled spores that can survive the winter.
This rust fungus was discovered on Koehne mountain ash (Sorbus koehneana) and Przewalski's juniper (Juniperus przewalskii), from Qinghai Province, north-western China.
Photo credit: Yingmei Liang and Chengming Tian