Resistance to powdery mildew in barley cultivars and breeding lines included in 1998-2000 Polish registration trials.

A total of 46 barley cultivars and breeding lines (35 spring and 11 winter) tested in 1998 - 2000 Polish registration trials were tested for powdery mildew resistance with 23 differential isolates of E. graminis f. sp. hordei. The isolates were chosen according to differences in virulence spectra that were observed on \'Pallas\' isoline differential set and on 8 additional differential cultivars. The experiment was conducted in the IHAR Radzików greenhouse 1999-2000.From 35 tested spring cultivars and breeding lines 6 (17%) were composed of different lines carrying different genes for resistance. Eight different resistance alleles [Mla1, Mla7, Mla12, Mla6, Mla14, Mlg, Ml (CP) and mlo] were detected alone or in combinations. Among tested cultivars and breeding lines of spring barley, majority (94%) had combination of different genes for resistance. The most common resistance gene was Mla12 and this gene was present in 12 (34%) spring breeding lines. Seven spring cultivars and breeding lines possessed Mlo resistance.Seven different resistance alleles [Mla12, Mla6, Mla14, Mla13, Ml (Ru3), Ml (Bw), Mlra] were detected alone or in combination in tested winter cultivars and breeding lines. From 11 tested cultivars and breeding lines of winter barley 3 were composed of different lines carrying different genes for resistance. Majority (91%) of these cultivars and breeding lines had combination of different genes for resistance. Major strategies for control of powdery mildew using resistance genes are discussed.