Canadian Forest Service Publications
A sensitive real-time PCR assay for the detection of the two Melampsora medusa formae speciales on infected poplar leaves. 2013. Boutigny, A.-L.; Guinet, C.; Vialle, A.; Hamelin, R.; Frey, P.; Ioos, R. Eur. J. Plant Pathol. 136:433-441.
Issued by: Laurentian Forestry Centre
Catalog ID: 35280
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Melampsora medusae is a quarantine fungus in the European Union (EU) that causes a damaging leaf rust disease on poplars. Two formae speciales of the pathogen can be distinguished, M. medusae f. sp. deltoidae and M. medusae f. sp. tremuloidae, but the EU plant health directive 2000/29/EC currently in force does not make the distinction between them. EU countries must have the ability to detect and identify rapidly the introduction of these quarantine fungi and to conduct extensive surveys in case of outbreaks. Efficient detection tools are thus needed. In this study, a sensitive real-time PCR assay was developed to detect the presence of M. medusae in poplar leaf samples. A unique primer/hydrolysis probe combination targeting both formae speciales was designed using species-specific polymorphisms observed within the internal transcribed spacer region. An additional primer/hydrolysis probe combination was designed from a region of the 28S rDNA that is highly conserved in the genus Melampsora and used in a separate real-time PCR assay in order to check the quality of the DNA extracted from Melampsora urediniospores. The test developed demonstrated a high sensitivity since it enables the reproducible detection of two M. medusae urediniospore in a mixture of 2 mg of urediniospores (ca 800 000 urediniospores) of other Melampsora species. This new real-time PCR tool should be useful for laboratories in charge of official analyses since it has many advantages over the techniques currently used to monitor this quarantine pathogen in Europe.
Plain Language Summary
The fungus Melampsora medusae is the pathogen responsible for poplar rust, considered one of the most damaging poplar diseases in the world. It causes early defoliation, which often results in reduced growth. In Europe, this rust species is considered a quarantine species by the European and Mediterranean Plant Protection Organization and its presence is closely monitored. There are two types of this rust fungus: f. sp. deltoidae (the host of which is the eastern cottonwood) and f. sp. tremuloidae (the host of which is the trembling aspen). Although European plant health units do not differentiate between the two, it is very important to have quick methods for detecting these two types of rust in order to prevent them from spreading far and wide.
The objective of this study conducted in Europe was to develop quick and reliable tests for detecting the presence of these two types of rust in nurseries. Tests were carried out using a technique based on the detection of the pathogen’s DNA molecules.
This test can be used for phytosanitary control purposes in order to prevent the introduction and spread of this rust in Europe. In Canada, this disease is present everywhere and trees have developed defence mechanisms to fight it.