Powdery mildew resistance in barley landraces from Morocco

Nineteen barley landraces collected from Morocco were screened for resistan ce to powdery mildew. The landraces originated from the collection at the P olish Gene Bank, IHAR Radzikow, Poland. The fifteen landraces tested showed powdery mildew resistance reactions and 35 single plant lines were selecte d. Twenty-one of these lines were tested in the seedling stage with 30, fou r lines with 17 and another 10 Lines with 23 differential isolates of powde ry mildew, respectively. The isolates were chosen according to their virule nce spectra observed on the Pallas isolines differential set. Nine lines (E 1029-1-1, E 1042-2-2, E 1050-1-1, E 1054-5-1, E 1056-2-5, E 1056-3-1, E 106 1-1-1, E 1061-1-3 and E 1067-1-2) which originated from seven landraces sho wed resistance to all prevalent European powdery mildew virulence genes. Th e most frequent score was 2 and 16 lines showed this reaction for inoculati on with most isolates used. The distribution of reaction type indicated tha t about 77% of all reaction types observed were classified as powdery milde w resistance (scores 0, 1 and 2). In all lines the presence of unknown gene s alone or in combinations with specific ones was postulated. Four differen t resistance alleles (Mlat, Mla6, Mla14 and Mla12) were postulated to be pr esent in 10 tested lines alone or in combination. Alleles Mint, Mla6 and Ml a14 were postulated to be present in four and Mla12 in two tested lines, re spectively. The value of barley landraces for diversification of resistance genes for powdery mildew is discussed.