The present study was performed at Gemmeiza Agricultural Research Station in 2015 season. Antisera were raised in white New-Zealand rabbits against antigens of three sugar beet varieties, Puma (resistant), Kawemira (moderately susceptible) and Herkl (susceptible) as well as conidia of the fungus Erysiphe betae. Using rossed immuno electrophoresis technique (CIE), 7, 7 and 8 precipitin peaks were detected when antigens of Puma , Kawemira and Herkl varieties reacted with its specific antibodies (homologous reactions). Also, eight precipitin peaks were detected when antigens of the fungus
Erysiphe betae reacted with its specific antibodies. However, in heterologous reactions, 3, 5, 6 common precipitin peaks (common antigens) were detected when antigens of Puma, Kawemira and Herkl reacted with antibodies of Erysiphe betae, respectively. The phenomenon of common antigens sharing plant hosts and its parasites has been interpreted in an attempt to explain the basis of susceptibility or resistance to diseases. The more antigenic similarity means the most susceptibility in host-pathogen interaction. According to these phenomena, the Puma variety could be classified as the most resistant one which gave the lowest number of common antigens. While, the Herkl variety could be classified as the most susceptible followed by Kawemira variety. These results are coincide with those obtained under greenhouse and field conditions and gave evidence that CIE technique could help to have a quick knowledge about the response of sugar beet varieties to powdery mildew disease. However, this study is the first report to assessment of resistance in sugar beet powdery mildew using crossed immunoelectrophoresis technique.