Microsatellite analysis indicates that Puccinia psidii in Australia is mutating but not recombining

Puccinia psidii is considered a biosecurity threat in Australia because of its broad host range that includes many species of Myrtaceae which dominate Australian ecosystems. Since it was first reported in this country, in April 2010, there has been little information about the population structure of the pathogen. In this study, six microsatellite loci were analysed to determine the genetic relationship among rust specimens from different hosts and locations in Australia, New Caledonia, Hawaii and China. The Chinese and New Caledonian specimens share a multi-locus genotype with the majority of the Australian specimens. The results also indicated a close relationship between Australian and Hawaiian samples. At present, the P. psidii population in Australia is genetically uniform with no evidence of sexual recombination. Five of the 104 collections varied by one allele at single loci, indicating that mutations are common but persistence of the mutants in the population may be less common.