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The need for rapid molecular diagnostics to distinguish biotypes of the myrtle rust pathogen (Austropuccinia psidii)

Informally Refereed

Abstract

Austropuccinia psidii impacts numerous forest ecosystems world-wide by causing myrtle rust disease on many myrtaceous species, including guava (Psidium guajava), eucalypts (Eucalyptus spp.), rose apple (Syzygium jambos), and ‘ohi’a (Metrosideros polymorpha). First reported in 1884 on guava in Brazil, the rust has since been detected in tropical and subtropical areas worldwide. At least three biotypes of A. psidii have currently been identified (Stewart et al. 2017), including eucalypt and guava biotypes in Brazil, and the globally distributed pandemic biotype which infects multiple hosts. However, despite known genetic variation in this species and distinct invasive threats, we currently lack rapid methods to quickly distinguish among different biotypes. This becomes especially problematic as biotypes of the pathogen continue to expand their geographic ranges. Although myrtle rust is established in Florida, California, Hawaii, Puerto Rico, Australia, and New Zealand, the introduction of new biotypes to these areas poses an additional threat, which could be amplified if hybridization were to occur (McTaggart et al. 2017, Loope & La Rosa 2008). Methods currently exist to confirm the presence of specific biotypes (Machado et al. 2015, Bini et al. 2018), but we need cost and time effective tools to quickly distinguish among biotypes (current and proposed methods are compared in Table 1). Here we propose a framework for developing rapid, userfriendly diagnostic assays for distinguishing among different A. psidii biotypes.

Keywords

myrtle rust pathogen (Austropuccinia psidii), ecosystems, myrtaceous species

Citation

Sitz, Rachael A.; Kim, Mee-Sook; Cannon, Phil G.; Alfenas, Acelino C.; Glen, Morag; McTaggart, Alistair R.; Klopfenstein, Ned B.; Stewart, Jane E. 2020. The need for rapid molecular diagnostics to distinguish biotypes of the myrtle rust pathogen (Austropuccinia psidii). In: Reynolds, Gregory J.; Wilhelmi, Nicholas P.; Palacios, Patsy, compilers. Proceeding of the 66th Western International Forest Disease Work Conference; 3-7 June 2019; Estes Park, CO. WIFDWC: www.wifdwc.org. p. 213-214
https://www.fs.usda.gov/research/treesearch/61289