DEFENSE RESPONSE OF SOYBEAN (GLYCINE MAX) TO SOYBEAN CYST NEMATODE (HETERODERA GLYCINES) RACE 3 INFECTION

Soybean plant responses to Heterodera glycines (H. glycines) race 3 infection were compared between resistant (Peking, LiaoK89102 and Franklin) and susceptible cultivars (Liao dou 10 and Kaiyu 10) at 10, 17, 20, and 23 days after inoculation (DAI). After inoculation with H. glycines race 3, the isozymes of peroxidase, polyphenol oxidase, superoxide dismutase, and catalase from the soybean roots were investigated. The time-course analysis of electrophoresis pattern of peroxidase, polyphenol oxidase, and superoxide dismutase isozyme showed increased enzyme activity in both the resistant and susceptible cultivars following inoculation. However, the increase in the resistant cultivars was rapid and greater than that in susceptible cultivars. The newly induced polyphenol oxidase enzyme bands (Rf values 0.80) were recorded for the nematode-infected resistant roots at 10, 13, 17, 20, and 23 DAI and compared to the non-infected ones. A peroxidase isozyme band (Rf value 0.78) was only recorded in the nematode-infected resistant cultivars Peking and Franklin at 13 and 17 DAI, respectively. In the superoxide dismutase and polyphenol oxidase patterns, the remarkable difference between inoculated and control plants was the amount of enzyme. In both resistant and susceptible cultivars infected with nematode, the enzyme was more abundant than in the control roots.