Development of a New Tool to Detect <i>Melampsora medusae</i> f. sp. <i>tremuloidae</i> Causing Rust Disease on <i>Populus tremuloides</i>

<i>Melampsora</i> <i>medusae</i> f. sp. <i>tremuloidae</i> is a quarantine organism for the European Union. In North America, this fungus causes rust disease on <i>Populus tremuloides</i>. In Europe, <i>Populus tremula</i>, an aspen closely related to <i>P. tremuloides</i>, is widespread and plays an important ecological role. Introduction of <i>M. medusae</i> f. sp. <i>tremuloidae</i> into Europe could be a major risk if this <i>forma specialis</i> could evolve and become virulent on <i>P. tremula</i>. To date, no PCR-based assay exists to specifically detect <i>M. medusae</i> f. sp. <i>tremuloidae</i>. In this study, a sensitive and specific real-time PCR assay has been developed based on the 28S rDNA. The assay proved to be reliable using many real-time PCR kits and platforms. It can be used to monitor the introduction and the spread of <i>M. medusae</i> f. sp. <i>tremuloidae</i> in the context of phytosanitary regulations.