Oxidative responses of resistant and susceptible soybeans to soybean aphid (Aphis glycines Matsumura)

This research investigated the role of peroxidases in the defense response of soybean to the soybean aphid. Changes in protein content, peroxidase activity and isozyme profiles in response to aphid feeding were documented in V1 and V3 stages of tolerant (KS4202) and susceptible (SD76R) soybeans. Protein content was similar between infested and control V1 and V3 stage plants for both KS4202 and SD76R at 6, 16, and 22 days after aphid introduction.  Enzyme kinetics studies documented that KS4202 V1 and SD76R V1 and V3 control and aphid-infested had similar levels of peroxidase activity at the three time points evaluated. By contrast, KS4202 aphid-infested plants at the V3 stage had significantly higher peroxidase activity levels than control plants at 6 and 22 days after aphid introduction.  The differences in peroxidase activity observed between infested and control V3 KS4202 plants throughout the course of the experiment suggest that peroxidases may be playing multiple roles in the tolerant plant. Gels stained for peroxidase identified differences in the isozyme profiles of aphid-infested and control plants for both KS4202 and SD76R.