Association mapping of resistance to rust disease in poplar

International audience; The foliar rust caused by the fungus Melampsora larici-populina Kleb. is the most devastating disease affecting the European poplar plantations. We have identified a factor of quantitative resistance, Rus, inherited from the genotype Populus trichocarpa 101-74, which can reduce by 60% the level of infection in laboratory and which has a significant effect in field. This factor is localized on the genetic map of P. trichocarpa 101-74 based on the analysis of one F1 interspecific family P. deltoïdes x P. trichocarpa. Map based cloning of Rus is under development, fine mapping and construction of BAC contig are underway. The alignments with the sequence of P. trichocarpa Nisqually-1 makes it possible to target the area of interest. We defined an exploratory zone of approximately 400 kb on which we already detected 28 genes. Ten of them are re-annotated as Resistance Gene Analogs (RGAs). Predicted genes have been investigated as candidate genes for fine mapping and association study. Association between Rus and those candidate genes has been first investigated in a collection of 94 individuals of P. trichocarpa. The collection was phenotyped for rust resistance under control conditions and in the field. The individuals have been genotyped by EcoTILLING.