Myrtle Rust

Rust fungi typically have complex life cycles that include stages of sexual and asexual reproduction that occasionally occur on phylogenetically distinct host plants. Austropuccinia psidii's life cycle is quite controversial with one study showing that the rust is autoecious while another study finding it to be heteroecious but with an alternate host that has yet to be found. Looking at the fungus as a polycyclic pathogen, Stage I consists of aeciospores inoculating young leaf/shoot/fruit/flower bud. Once infected, aeciospores germinate and penetrate the host by creating a haustoria. Colonies and urediniosori forms after penetration. In Stage II, the production of urediniospores go back to inoculate young leaf/shoot/fruit/flower bud, important for secondary infection and contributing to the polycyclic nature of the pathogen. Stage II is also where urediniospores germinate, and penetration of the host occurs, resulting in the development of an uridiniosori. In Stage III, urediniospores germinate and the host is penetrated with the development of a haustoria. After penetration, colonies are formed and teliosori are developed. Teliosori produce teliospores which can further germinate. Once they're germinated, basidiospores are developed. In Stage IV, basidiospores are spread, inoculating young leaf/shoot/fruit/flower bud. …