Genomics of tree-microbe interactions

The spread of insects and diseases has been facilitated by increases in the international trade of agricultural and forest products. Global climate change also amplifies the occurrence and severity of pest outbreaks. Moreover, introduced forest pests can be extremely destructive since resistance is often nonexistent in natural populations. It is thus important to improve our understanding of tree defense response mechanisms against forest pests. The objectives of our project are the following:

• To improve our understanding of tree molecular defense mechanisms following infection by fungal pathogens to enable the development of new genetic markers.
• To identify new knowledge-based molecular markers for improving efficiency of breeding for resistance in trees.
• To integrate and develop new working hypotheses in relation to those target genes with the objective of developing and improving biological control methods.
• To assemble a list of candidate genes that could be used in trials with genetically modified trees.

With their long life cycle, trees must possess accurate mechanisms for detecting microbial invasions and elaborate signalling networks in order to activate the appropriate defense response. Thanks to the availability of its whole genome sequence, poplar (Populus) is now considered a model tree species for genomics research. Poplar is easy to grow and propagate by cuttings, and its genetic transformation is common practice. Moreover, genomes of a great number of associated microorganisms are being sequenced, including that of Melampsora poplar rust, a tree pathogen. With these tools in hand, the poplar-rust pathosystem holds great potential for the study of tree-microbe interactions at the molecular level. We have pursued various approaches to identify poplar genes involved in the interaction with the biotrophic Melampsora rust pathogen.

Poplar represents one of the most productive species for short rotation intensively managed plantations. The trend towards more intensive forest management will make it possible to meet our economic needs while addressing environmental concerns by allowing us to devote large natural areas to conservation. This trend is being seen worldwide: the FAO estimates that by 2050, 75% of all commercial wood harvested will come from plantations occupying only 5-10% of the forested areas. These gains, however, will only be realized if we can protect commercial tree cultivation from damaging diseases.