Abstract: The peroxidase isozymes in young and mature leaves (382 samples) from 40 mulberry varieties belonging to 3 species were tested with polyacrylamide gel electrophoresis on vertical plate in summer and autumn respectively. The conclusions are as following: 1. The peroxidase isozymes spectrum of mulberry varieties can be divided into 2 zyme regions-region A and region B. The range of relative electrophoretic mobility (Rf) of region A is 0.06-0.41, and that of region B-0.51-0.64. 2. In summer (June) the manifestation of the peroxidase isozymes in young and mature leaves in every periods is stable. The manifestation of the young leaves is more abundant than that of the mature leaves. 3. A₁, A₂,A₃, A₄ and A₇ bands are related to growth. 4. The manifestation of the main zyme bands in 40 mulberry varieties is similar, and the multerry varieties can be divided into two groups according to whether A₉ band is manifested or not. 5. The both groups include the mulberry species-Morus multicaulis P., Morus bombycis K., Morus alba L., which shows the identity in their inner gene. 6. Mulberry varieties are divided into 5 kinds on the base of the two groups according to the zyme band the manifestation of which in the young leaves is stable in summer.

Key words: Mulberry, Peroxidase, Isozymes, Gel electrophoresis