Basionym: Puccinia psidii G. Winter
Bright yellow uredinia develop on both sides of young leaves. Lesions are often produced on actively growing shoots, sepals and occasionally young fruits (Glen et al. 2007; Roux et al. 2013). Heavy infections can deform leaves and cause defoliation, tip dieback, loss of apical dominance and stunting (Coutinho et al. 1998). In severe cases, shoot death or death of susceptible individuals can be the result of multiple re-infections (Carnegie et al. 2016).
In the plant, leaf spots with abundant yellow spore masses can be observed on young shoots, leaves, flower buds, fruits and stems.
The yellow, powder-like urediniospores, range in size from 15 – 20 (x̅ = 19) x 12 – 16 (x̅ = 14) µm. Some urediniospores have smooth patches on their surface known as tonsures (Roux et al. 2013). Teliospores are cylindrical or ellipsoidal, 2-celled, pale yellowish to brown and smooth.
The life stages of A. psidii include urediniospores, teliospores and basidiospores (McTaggart et al. 2018). Two types of reproduction (sexual and asexual) can be distinguished in the life cycle of Austropuccinia psidii (Glen et al. 2007). The asexual stage is identified by urediniospores as their main structure for dispersal. The sexual stage starts with the teliospores that produce basidiospores after meiosis. Thus, compatible basidiospores are hypothesised to form a hymenium capable of producing uredinia or teliospores (McTaggart et al. 2018).
Carnegie AJ, Kathuria A, Pegg GS, Entwistle P, Nagel M, et al. 2016. Impact of the invasive rust Puccinia psidii (myrtle rust) on native Myrtaceae in natural ecosystems in Australia. Biological Invasions 18: 127-144.
Coutinho TA, Wingfield MJ, Alfenas AC, Crous PW. 1998. Eucalyptus Rust: A disease with the potential for serious international implications. Plant Disease 82: 819-825.
Glen M, Alfenas AC, Zauza EaV, Wingfield MJ, Mohammed C. 2007. Puccinia psidii: a threat to the Australian environment and economy – a review. Australasian Plant Pathology 36: 1-16.
Mctaggart AR, Shuey LS, Granados GM, Du Plessis E, Fraser S, et al. 2018. Evidence that Austropuccinia psidii may complete its sexual life cycle on Myrtaceae. Plant Pathology 67: 729-34.
Roux J, Greyling I, Coutinho TA, Verleur M, Wingfield MJ. 2013. The Myrtle rust pathogen, Puccinia psidii, discovered in Africa. IMA Fungus 4: 155-159.
