Date of this Version
Marchi, L.S. Investigating the Tolerance Response of Early Vegetative Stage Soybeans to Aphis glycines Matsumura (2012). MS Thesis, University of Nebraska-Lincoln.
The objectives of this research were to evaluate the impact of soybean aphid (Aphis glycines Matsumura) feeding on the yield response of V1, V3, and R1 KS4202 soybean plants and examine the effect of soybean aphid feeding on peroxidase activity in V1 and V3 KS4202 plants. KS4202 plants infested during the early vegetative stages (VC, VE and V1) were identified as highly susceptible based upon plant damage and stunting of the plants. In contrast, V3, V4, and V5 stage KS4202 soybeans were classified as moderately resistant. In the yield response study, V1, V3 and R1 plants had aphid numbers that exceeded the average economic injury level threshold of 674 aphids per plant. Despite exceeding this level, V3 and R1 aphid-infested plants were not statistically different from their respective control plants for any of the yield parameters evaluated except average pod weight, which was statistically higher for plants exposed to the high aphid treatment than to the control treatment. 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 at 6, 16, and 22 days after aphid introduction. 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 soybean 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 peroxidases identified differences in the isozyme profiles of aphid-infested and control plants for both KS4202 and SD76R. The results of this research provide insights to better understand the tolerance response in KS4202 and ultimately will result in improved management options for this important insect pest.
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