1Sanya Institute of Hainan Academy of Agricultural Sciences，Hainan Experimental Animal Research Center，Sanya 572025，Hainan，China；2Hainan Sanya Crops Breeding Trial Center of Xinjiang Academy Agricultural Sciences，Sanya 572000，Hainan，China；3Center of Hami Melon，Xinjiang Academy of Agricultural Sciences，Urumqi 830091，Xinjiang，China
Abstract：Sanya city is an important producing area of Hainan Melon，and also a high-incidence area of melon powdery mildew．This study identified the physiological race of powdery mildew pathogen naturally occurring at Sanya melon test base by using microscopic，molecular biology methods，and 13 internationally recognized standard identification hosts．Besides，the study chose 30 materials from the self-selected 4th generation melon germplasm resources for identification and screening of resistance to powdery mildew during seedling stage．Results showed that through analysis on morphological characteristics of pathogenic spores，
bacteria ITS sequences alignment，and inductive reaction of 13 standard hosts to powdery mildew pathogen inoculation，the pathogen was determined to be the Race 2France of Podosphaera xanthii．Additionally，2 materials（22-7-2，22-16-1）were found to be immune to powdery mildew out of 30 thick-skinned melons；and 3 were found to be highly resistant to powdery mildew（06-4-1，14-8-1 and 23-8-1）．The 2 immune materials were all of yellow-skinned，elliptical，and reticulated types．While，the 3 were all high-resistant materials of reticulate type．
