Simple sequence repeat markers support the presence of a single genotype of Puccinia psidii in Australia

A non‐native rust of Myrtaceae was first detected in Australia in 2010, and was later identified as Puccinia psidii . The presence of many native species of Myrtaceae and a lack of understanding of genetic variability in P . psidii in Australia led to the current study. Low coverage genome sequencing of P. psidii suggested a genome size of c . 142 Mb. A set of 240 simple sequence repeat ( SSR ) primers was designed based on the genome sequence information generated. Seventeen isolates of P . psidii comprising 14 from Australia, two from Brazil and one from Hawaii were selected to study genetic variation in the pathogen. Out of 240 initially screened markers, 74% showed amplification among P . psidii isolates and 38% were polymorphic. Primers were fluorescently labelled and genotyping revealed three distinct genotypes among the isolates: one comprising Australian isolates and an isolate from Hawaii, and the second and third comprising two Brazilian isolates. Locus USYD _ Pp 151 produced a fourth genotype for the Hawaiian isolate of P . psidii . Markers revealed that all Australian isolates were genetically similar to the one from Hawaii. There was no genetic variation among the Australian isolates of P . psidii , supporting the hypothesis that only one genotype of P . psidii was introduced into Australia. The SSR markers developed in this study are highly specific to P . psidii and can be used confidently as a new profiling tool to monitor evolution of P . psidii in Australia and elsewhere.