Molecular genetics of rust resistance in poplars (Melampsora larici-populina Kleb/Populus sp.) by bulked segregant analysis in a 2 x 2 factorial mating design.

With random amplified polymorphic DNA (RAPD) markers, we have tagged a genomic region in Populus sp. involved in qualitative resistance to Melampsora larici-populina. Our approach was based on three steps: use of RAPD markers that can be quickly and efficiently researched: application of "bulked segregant analysis" technique on individuals of one interspecific family P. trichocarpa x P. deltoides to search for RAPD markers linked to resistance; and validation of these markers in two other families linked with the first one in a 2 x 2 factorial mating design. Of five detected markers, only one marker M03/04_480 was polymorphic in the three segregating families, involving 89 individuals and four different parents. We have estimated the recombination value of 1 cM with 1 cM sampling error.