The genetic control of the specific interactions PG3-Quinta and PG2-Glacier was analysed on both the pathogen and the plant side at the cotyledon stage. On the pathogen side, tetrad analysis was performed following crosses between (i) PG3 and PG4 isolates and (ii) PG2 and PG4 isolates. On the plant side, Quinta and Glacier were crossed with a blackleg susceptible winter cultivar, Score. The genetic control of specific resistance was established following the analysis of Fl, F2 and test-cross populations. Our data suggested that the incompatible interactions PG3-Quinta and PG2-Glacier were conditioned by pairs of matching avirulence-resistance genes, Avrlm1-Rlm1 and Avr2m-2Rlm2, respectively. Elements to elucidate the genetic basis of the PG2-Quinta interaction were also obtained. A third avirulence gene, AvrLm3, could be responsible for the incompatibility of PG2 isolates towards Quinta. Evidence for the: presence of a third corresponding resistance gene operating in Quinta has now to be demonstrated.