我国是世界西瓜生产与消费第一大国,西瓜收获面积占全球总面积的58.06%,产量占全球总产量的76.5%(赵姜和吴敬学,2012)。采用嫁接栽培可以提高西瓜对土传病虫害的抗性,但西瓜嫁接苗生产中育苗温室内相对的高温和高湿环境容易导致病虫害的发生蔓延(别之龙,2011)。2014年以来,在北京市西瓜种植区的育苗温室内,用南瓜嫁接砧木的幼苗上发生一种褐斑病,导致嫁接苗长得弱小。目前国内外还未见关于该病害的研究报道。为明确 China is the largest producer and consumer of watermelon in the world. The watermelon harvested area accounts for 58.06% of the global total and its output accounts for 76.5% of the global output (Zhao Jiang and Wu Jingxue, 2012). Grafting cultivation can improve watermelon resistance to soil-borne pests and diseases, but the watermelon grafted seedlings in the production of greenhouse seedlings in the relatively high temperature and high humidity environment easily lead to the occurrence of pests and diseases (Other Dragon, 2011). Since 2014, a brown spot has emerged on seedlings of pumpkin-grafted rootstocks in watermelon-growing greenhouses in Beijing’s watermelon growing areas, resulting in grafted seedlings that grow weakly. At present, no reports on the disease have been reported at home and abroad. To be clear