Rust (fungus) - Spores

Spores

Rusts can produce up to five spores types during their life cycle

• 0-Pycniospores (Spermatia)-Haploid gametes in heterothallic rusts.
• I-Aeciospores-non-repeating dikaryotic vegetative spores
• II-Urediniospores-repeating dikaryotic vegetative spores. These spores are referred to as the repeating stage because they can cause auto-infection (re-infect the same host from which the spores were borne). These spores are red/orange and are a characteristic sign of rust fungus infection.
• III-Teliospores-Diploid spores that produce basidia and are the survival stage of life cycle
• IV-Basidiospores-stem from basidia. Haploid spores which infect the alternate host. although these are rarely observed outside of the laboratory.

Rust fungi can be categorized by how many types of spores are produced during the life cycle. Fungi that produce all five spores (sometimes excluding pycniospores) are termed macrocyclic. Fungi that lack pycniospores and aeciospores in their life cycle are termed microcyclic and always have an autoecious life cycle. Demicyclic fungi delete the uredial (repeating) stage from the life cycle. Understanding the life cycles of rust fungi allows for proper disease management.