Tracking the distribution of Puccinia psidii genotypes that cause rust disease on diverse myrtaceous trees and shrubs

Puccinia psidii Winter (Basidiomycota, Uredinales) is a biotrophic rust fungus that was first reported in Brazil from guava in 1884 (Psidium guajava; Winter 1884) and later from eucalypt in 1912 (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 USA (California, Florida, and Hawaii), Japan, Australia, China, and most recently South Africa and New Caledonia (Figure 1; Maclachlan 1938, Marlatt and Kimbrough 1979, Mellano 2006, Uchida et al. 2006, Kawanishi et al. 2009, Carnegie et al. 2010, Perez et al. 2011, Zambino and Nolan 2011, Zhuang and Wei 2011, Roux et al. 2013, Rayamajhi et al. 2013). Given the rate at which the pathogen is spreading and its wide host range, the objectives of this study were to estimate genetic diversity within and among populations across the species native range as well as areas of recent introduction, evaluate possible pathways of spread, and predict geographic areas that are climatically suitable in order to predict risk of invasion.