The reaction of five different Plasmopara halstedii isolates has been
analysed on a range of differential genotypes. Four isolates had a sim
ilar reaction to race 1 (the European race). However one isolate had t
he ability to infect genotypes with no gene of resistance and also the
line Rha 266 (Pl1) which is resistant to race 1. The reaction of this
isolate was similar to that of the American race 2. This is the first
record of this race in Morocco.