REGIONAL DISTRIBUTION OF RESISTANCES TO POWDERY MILDEW IN WINTER AND SPRING BARLEY CULTIVARS GROWN IN THE NORTHERN PART OF FRANCE

The spatio-temporal distribution of race-specific resistances to powde ry mildew was analysed in northern France (the east, the north and the west of Paris). Resistances were identified in 26 winter and six spri ng barley cultivars. Seedling leaf segments were inoculated with 20 po wdery mildew isolates, chosen to identify 14 resistance alleles. As op posed to other European countries, the resistance alleles differed bet ween winter and spring cultivars grown in the three regions. Most of t he winter cultivars had no resistance allele, or only the widespread r esistance alleles Mlra and/or Mlh, plus Mlg in the west. Mla9 and Mla1 3 were also present in the north, but at a low frequency. Spring culti vars carried the alleles Mla7, Mla9, Mla12, Mlk, Mlg or MlLa in the ea st, where a diversification of resistances has occurred since 1987, pa rticularly because of the use of 'Volga' (Mla7, Mlk, Mlg and MlLa). In the north and the west, Mla12 dominated after a decrease in the frequ ency of Mla7. Mla13 has recently been introduced in the north and the west with the cultivar 'Vodka'.