Abstract: Leaf mould (Fulvia fulva Cooke Ciferri) is one of the serious diseases on tomato under protective cultivaion (greenhouse and plastic house) . In the program of tomato breeding for resistance to leaf mould, it is important to determine the extent of physiological races of leaf mould. Between 1984 and 1990, the races 1. 2 and 1. 2. 3 were found in Beijing. The gene Cf₄ was immune from those races. So a resistant variety (F1) Shuang Kang. 2 with Cf 4 was first introduced in tomato production. In 1990, that hybrid was attacked by the new races of 1. 2. 4, 2. 4 and 1. 2. 3. 4. Another hybrid Jia Fen. 15 with Cf₄ and Cf₅ was developed. It was resistant to the new races found in 1990. Although the six races had no obvious difference in virulence from those races in 1990, the virulence of a few isolations strengthened in a certain degree. The gene Cf₅ came to show no more immunity. Occassionally, a little amount of the mould could be found on the host plants with Cf₅. The breeders have to pay more attention to this matter.

Key words: Tomato, Leaf mould:Physiological race, Vertical resistance