一、前言广东新会县荷塘一带盛产蕪菁[根用蔬菜,俗称冲菜,Brassica juncea(Linn.)Coss.],远銷国內和海外各地。蕪菁除受肿根病(Plasmodiophora brassicae Worn.)、軟腐病Erwinia carotovora(Jones)Burg.]和花叶病[Brassica virus 2(Turnip virusl),Hoggan and Johnson]严重为害外,尚受