II strain of soybean mosaic virus (SMV). 2 types occurred in F_(1): symptomless and top necrosis, and 3 types in the F_(2) plants: symptomless, with symptom(mosaic, wrinkle and so on)and top necrosis.

• F_(1)表现两种类型: 无症株和坏死株, F_(2)表现三种类型: 无症株、 有症株(花叶、皱缩等)和坏死株。