What is "roesler"

Roesler is a red Austrian wine grape developed in 1970 by Dr. Gertraud Mayer at Höhere Bundeslehranstalt und das Bundesamt für Wein- und Obstbau in Klosterneuburg, Austria. It is the result of a crossing Zweigelt x (Seyve-Villard 18-402 x Blaufränkisch) and is named after the former director of Austria's oldest viticultural college, Leonard Roesler. The variety is deep in color and with abundant extract. It is frost resistant and can withstand temperatures as low as -25ºC (-13ºF). It is also resistant to mildew.