Identification of powdery mildew resistance genes in common wheat (Triticum aestivum L). II. French cultivars

— Major genes for resistance to the wheat powdery mildew pathogen, Erysiphe graminis f sp tritici, were analysed in 35 French wheat cultivars and in part in their parents. Cultivars were tested with a set of differential pathogen isolates which had specific interactions for each host line. The results were supplemented by cytological investi- gations and by consideration of pedigrees. Eighteen cultivars showed susceptible reactions. The remainder formed 9 groups with 1 or 2 resistance genes. Of the 5 known resistance genes present, Pm2 was the most common (in 5 culti- vars), followed by Pm4b and Pm6 (each present in 4 cultivars), Pm5 (3 cultivars) and Pm8 (2 cultivars). In addition, an unknown resistance, tentatively designated Mlar, was identified in 3 cultivars.