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POSTERS: Disease Detection and Diagnosis I

P-159 - Development of diagnostic tools to mitigate threats associated with the invasive myrtle rust pathogen, Austropuccinia psidii

Monday, August 4, 2025
3:45 PM - 4:30 PM HST
Location: Exhibit Hall 3
Abstract Text: The invasive myrtle rust pathogen, Austropuccinia psidii, infects numerous Myrtaceae species around the world. Microsatellite markers have defined four different biotypes of A. psidii, and each biotype has distinct host associations and geographic distribution, with some overlap. The biotypes include the South African biotype in South Africa, the guava and the eucalypt/rose apple biotypes in South America, and the Pandemic biotype in regions of Oceania and Hawaii, southeastern Asia, Central America, the Caribbean, and Colombia. Previous bioclimatic modeling determined geographic areas with suitable climate spaces for each A. psidii biotype, which also identified new geographic regions suitable for biotype establishment. Consequently, potential introductions of A. psidii biotypes to new regions is a major concern. To help prevent the spread of A. psidii biotypes, we developed loop-mediated, isothermal DNA amplification assays for distinguishing the four known biotypes of A. psidii. The assays were tested using purified DNA and crude-extracted, urediniospore-derived DNA from infected-plant samples. However, recent assays of myrtle rust samples collected from host trees in Brazil showed cross-reactivity with the Pandemic biotype. Genome sequencing and assembly of two of these A. psidii samples showed a closer similarity to the Pandemic biotype to other biotypes, particularly a sample from java plum (Syzygium cumini); however, these samples varied at the microsatellite loci. The implications of this findings will be presented and discussed.