Genetic and genotypic diversity of Puccinia psidii - the cause of guava/eucalypt/myrtle rust - and preliminary predictions of global areas at risk

Puccinia psidii (Basidiomycota, Uredinales) is a biotrophic rust fungus that was first reported in Brazil from guava (Psidium guajava) in 1884 (Winter 1884) and later from nonnative eucalypt (Eucalyptus capitelata and Corymbia citriodora, syn. Eucalyptus citriodora; Joffily 1944). Considered to be of Neotropical origin, the rust has also been reported to infect diverse myrtaceous hosts elsewhere in South America, Central America, the Caribbean, Mexico, the United States (California, Florida, and Hawaii), Japan, Australia, China, and most recently South Africa and New Caledonia (Carnegie et al. 2010; Giblin 2013; Kawanishi et al. 2009; MacLachlan 1938; Marlatt and Kimbrough 1979; Mellano 2006; Perez et al. 2011; Roux et al. 2013; Uchida et al. 2006; Zambino and Nolan 2011; Zhuang and Wei 2011). Given the rate at which the pathogen is spreading and its wide host range, the objectives of this study are to determine how much genetic diversity exists within populations across the species’ putative native range as well as areas of recent introduction, evaluate possible pathways of spread, and predict the geographic area that is climatically suitable for the species to determine areas at risk of invasion.