Identification of physiological races of cucurbits powdery mildew in Guanzhong areas,Shaanxi Province

【Objective】In order to control local cucurbits powdery mildew and breed new resistant varieties,the physiological races were identified in Guanzhong areas,Shaanxi Province.【Method】Thirty eight pathogen collections of powdery mildew obtained from cucurbits under different conditions of cultivation were detected for physiological races of cucurbits powdery mildew by a set of internationally recognized melon differential hosts.【Result】The observation from microstructure and ultrastructure to Podosphaera xanthii indicated that all 38 powdery mildews collected were P.xanthii.They were highly susceptible to I-ran H,Topmark,Vedrantais,PMR 45 and Nantais Oblong;immune to PMR 5,PMR 6,Edisto 47 and WMR 29,resistant to PI 124111,PI 124112,PI 414723 and MR 1,and occured as the same reaction as 2F.of P.xanthii.【Conclusion】It could be preliminarily confirmed that physiological race of cucurbits powdery mildew was the race 2F.of P.xanthii and no other races were discovered in Guanzhong areas,Shaanxi Province.