First report of myrtle rust caused by Austropuccinia psidii on Rhodomyrtus tomentosa (Myrtaceae) from Singapore.
A. psidii (formerly Puccinia psidii) causes rust on species of Myrtaceae. Since 2006, different genotypes of A. psidii have spread to countries in the Pacific and to South Africa. The pathogen was recently discovered on Eucalyptus pellita and Melaleuca leucadendra in Indonesia. Three suspected specimens of A. psidii were collected in August 2016 from Singapore on leaves of R. tomentosa (Myrtaceae), a tree native to southeastern Asia. The symptoms were the same as those caused by this pathogen with unmistakable yellow pustules of uredinia on the young leaves and inflorescences. Based on morphological characteristics and molecular data (sequence analysis of the rDNA internal transcribed spacer and large subunit regions), the causal agent was identified as Austropuccinia psidii. This is thought to be the first report of myrtle rust caused by A. psidii on R. tomentosa from Singapore.