Présence au Maroc de la race 2 de Plasmopara halstedii, agent du mildiou du tournesol

Des tests de laboratoire réalisés sur des isolats marocains de mildiou ont mis en évidence l'existence, en plus de la race 1 dite race «Européenne», d'une race plus virulente qui a le même comportement que la race 2 américaine.Plasmopara halstedii race 2 of downy mildew is present on sunflower in Morocco. The reaction of five different Plasmopara halstedii isolates has been analysed on a range of differential genotypes. Four isolates had a similar reaction to race 1 (the European race). However one isolate had the ability to infect genotypes with no gene of resistance and also the line Rha 266 (PI1) 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