Title: Nitrogen Fixation, Ureide, and Nitrate Accumulation Responses to Soybean Aphid Injury in Glycine max Authors
Submitted to: Journal of Plant Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 27, 2008
Publication Date: September 21, 2009
Citation: Riedell, W.E., Catangui, M.A., Beckendorf, E.A. 2009. Nitrogen Fixation, Ureide, and Nitrate Accumulation Responses to Soybean Aphid Injury in Glycine max. Journal of Plant Nutrition. 32:1674-1686. Interpretive Summary: The soybean aphid, a common soybean insect pest in Asia, was first found in Wisconsin during July 2000. Once established on a plant, soybean aphid populations can increase logarithmically via asexual reproduction. Soybean aphids also can develop winged form body morphology during summer months which allows the insect to spread through the air to infest large geographic areas, even in areas where the aphid does not overwinter. By 2003, the insect was found in 21 U.S. states and 3 Canadian provinces and is now considered to be a major soybean insect pest in the north central US. Predictions are that this insect will expand its range to include all regions of the US where soybeans are grown. Because the soybean aphid is a new pest in the U.S., a comprehensive integrated pest management (IPM) approach to manage aphid populations has yet to be developed. We felt that a controlled environment study of the influence of soybean aphid on growth and N relations would be a step toward understanding the mechanism of how soybean plants respond to the stress caused by this insect pest. Increased understanding might help breeders develop tolerant soybean lines or may suggest new ways to manage the crop to reduce biological stress caused by this aphid pest. The objectives of this study were to measure the effects of soybean aphid infestation, applied at different soybean development stages, on soybean plant growth, nitrogen (N) fixation, and N assimilation. Our results suggest that soybean aphid populations that build up just prior or during soybean reproductive stages could be more damaging to plants grown in N deficient soils than soils with higher residual N. The results of this study also suggest that it may be possible to use N fertilizer applications to soybeans as a way to ameliorate feeding damage caused by soybean aphid feeding in soils with low residual N. Additional studies would need to be conducted to test these hypotheses.
Technical Abstract: Knowledge of soybean aphid (Aphis glycines Matsumura) feeding effects on soybean (Glycine max [L.] merr.) physiology is needed to develop crop management methods that reduce biological stress caused by this insect pest. Controlled-environment studies were conducted to measure soybean aphid infestation effects on growth, nitrogen (N) fixation, and N assimilation. For N fixation experiments, plants grown using –N nutrient solution culture were infested at the 3rd trifoliolate (V3) stage and measured for N fixation and nodule characteristics at the full pod (R4) stage. Aphid infestation reduced total nodule volume plant-1 by 34%, nodule leghemoglobin plant-1 by 31%, and N fixation rate plant-1 by 80%. For N assimilation experiments, soil-grown plants were infested at the 1st trifoliolate (V1) or beginning bloom (R1) stage and shoots were measured 30 d later for dry weight, nitrate N, ureide N, and total N. Infestation at V1 reduced shoot dry weight by 63%, increased nitrate N concentration by 75%, and did not significantly affect ureide N concentration. Infestation at R1 caused no significant effects on shoot dry weight or nitrate N but did reduce ureide N concentration and accumulation. We conclude that these ureide N responses in infested soybeans resulted because N fixation (and subsequent ureide N accumulation) was more sensitive to aphid damage than shoot dry weight accumulation or nitrate N accumulation. Thus, soybean aphid populations that build up just prior or during soybean reproductive stages could be more damaging to plants grown in N deficient soils than soils with higher residual N.