Abstract: Three different resistant cultivars of soybean, high disease-resistant (Xingxian huibuzhihedou), middle disease-resistant (Yingxian xiaohedou), or sensitive (Lee, U S), were used to study the changes of peroxidase (POD) activity and isoperoxidase (SOD) in the course of SCN infection. The results showed that the disease-resistant soybean cultivars, may increase their peroxodase activity in order to resist an attack of SCN. The POD isoenzyme activity fluctuated in the course of resisting SCN attack. During the peak period of attack (30-35 days) the activity of high-resistant cultivar was higher than those in the other two cultivars, and the color of isoperoxidase was more than those of the other two cultivars. Whereas the value of POD activity of the sensitive cultivar became the lowest in the same period, and the number of the bands decreased, and some of them even disappeared. Besides, it was found that POD participated the synthesis of lignin in the process of resisting SCN attack. So both the value of POD activity and expression style can be considered as a physiological index to evaluate the resistance to SCN.

Key words: Peroxidase, Isoenzyme, Soybean cyst nematode