莴苣(Lactuca sativaL.)又名生菜、莴笋,属菊科舌状花亚科莴苣属,莴苣有茎用莴苣(莴笋)(var.as-paragina Bailey)、皱叶莴苣(var.crispa L.)、直立莴苣(var.longifolia Lam.)、结球莴苣(var.capitata L.)4个变种。莴苣霜霉病(Lettuce downy mildew)是由莴苣盘霜霉(Bremia lactucae Regel)引起的一类常见世界性真菌病害,1960年首次在阿拉斯加州报道(Logsdonetal.,1960),之后1979年首次在我国报道(Tai,1979),随后在澳大利亚、奥地利、巴西、美国加州、加拿大、古巴、德国、韩国、新西兰等40多个国家 Lettuce (Lactuca sativa L.), also known as lettuce, lettuce, belongs to Asteraceae subfamily Lactuca, lettuce with lettuce (lettuce) (var.as-paragina Bailey), lettuce (var. Crispa L.) , Four varieties (var. Longifolia Lam.) And lettuce (var. Capitata L.). Lettuce downy mildew is a common worldwide fungal disease caused by Bremia lactucae Regel, first reported in Alaska in 1960 (Logsdon et al., 1960), and then for the first time in 1979 (Tai, 1979), followed by more than 40 countries including Australia, Austria, Brazil, the United States, California, Canada, Cuba, Germany, South Korea and New Zealand