IDENTIFICATION OF POWDERY-MILDEW-RESISTANCE GENES IN COMMON WHEAT (TRITICUM-AESTIVUM L EM THELL) .5. OLD GERMAN CULTIVARS AND CULTIVARS RELEASED IN THE FORMER GDR

A total of 59 old wheat cultivars grown in Germany prior to 1960 were tested for mildew response using a collection of 12 differential isola tes of Erysiphe graminis DC f. sp. tritici Marchal (Blumeria graminis (DC) Speer f. sp. tritici). Nineteen cultivars did not possess any maj or resistance gene and 25 were characterized by susceptible or interme diate responses. Fifteen cultivars revealed isolate-specific response patterns that could not be attributed to known major resistance genes or gene combinations. Many of the old German cultivars inherited a mil dew-resistance gene from the Canadian cultivar 'Garnet', which is tent atively designated Ml-Ga. Cultivars 'Bretonischer Bartweizen' (designa ted Ml-Br) and 'Adlungs Alemannen' (designated Ml-Ad) appeared to carr y unknown resistance genes. Among 18 winter wheat cultivars released i n the former GDR, eight showed susceptibility to all isolates used. Cv . 'Borenos' carries resistance gene Pm3c. Five cultivars possess gene Pm4b, two cultivars gene pm5 and one cultivar a combination of genes P m2 and Pm4b. Cultivar 'Zentos' was resistant to almost all isolates us ed. Its resistance might be conditioned by different unknown major res istance genes.