Resistance of 'Roxana' to powdery mildew and its presence in some European spring barley cultivars

In the last two decades, powdery mildew resistance has been investigated in a large number of barleys grown in the Czech Republic. Apart from those with the Mlo resistance, 29 spring barley cultivars were as fully resistant. In this study, tests on 22 of these cultivars are presented. Forty reference isolates of Blumeria graminis f. sp. hordei, including five isolates collected in 2008, were used. Two of the latter were virulent on 18 cultivars including 'Havanna', 'Marnie' and 'Roxana'. 'Roxana' derived its resistance from wild barley accession 1B-86B, and was the first cultivar registered with this resistance. It is recommended that this resistance be designated Ro. According to their pedigrees, the resistances of 'Andrey' and 'Lilly' were also derived from 'Marnie'. It is likely that the resistance of IN 0614 and NORD 06/1108 is Mlo. Thus, among the 29 cultivars, there are only two resistances, and only Mlo remains fully resistant.