|CATANGUI, MICHAEL - Consultant|
Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/11/2012
Publication Date: 1/4/2013
Citation: Riedell, W.E., Beckendorf, E.A., Catangui, M.A. 2013. Soybean aphid injury effects on shoot N components in Glycine max. Crop Science. 53:232-239. doi: 10.2135/cropsci2012.05.0286.
Interpretive Summary: The soybean aphid, Aphis glycines (Matsumura), was first detected in the U.S. in 2001. This invasive insect expanded its geographic range and is currently considered to be a major insect pest of soybeans in the north central U.S. Because soybean is a major crop of economic importance in the U.S., development of integrated pest management systems and soybean varieties resistant to soybean aphids are important priorities. Basic understanding of the physiological and biochemical mechanisms of soybean crop injury and yield loss caused by aphid feeding is an essential step towards meeting these priorities. We advance in this paper the results of a 2 year field study where known numbers of aphids were applied to caged soybean plants at a specific time during vegetative plant growth. Aphid populations, plant growth and biochemical parameters were then measured during the reproductive stages of the soybean plant. Research findings indicate that aphid feeding injury reduces the biosynthesis of nitrogen-containing compounds derived from the energy-intensive process of nitrogen fixation to a greater extent than the root absorption of nitrogen-containing compounds from the soil. These findings suggest that soil nitrogen fertility could be an important component in crop management that could reduce plant injury and yield loss to the soybean aphid.
Technical Abstract: Knowledge of soybean aphid (Aphis glycines Matsumura) feeding effects on soybean (Glycine max [L.] merr.) shoot N components may improve understanding of how plants are injured by this invasive pest. This 2-year field study was conducted to measure soybean aphid (SA) effects [initial infestation of 0, 10, 50, or 100 aphids plant-1 at the fifth node (V5) stage] on SA populations, shoot dry weight (DW), nitrate-N, and ureide-N measured at full bloom (R2), beginning pod (R4), full pod (R5), and beginning seed (R6). Across both years, SA (aphids plant-1) were relatively low at R2 (1535), increased logarithmically through R4 (7724), peaked at R5 (15506), then decreased dramatically at R6 (2123). Shoot DW was not significantly different across control and SA treatments at R2 but compared to control was reduced by 100 SA plant-1 at R4. At R5 and R6, all SA treatments reduced DW to an equal extent. Compared with control, all SA treatments increased shoot nitrate-N concentration about 45%, suggesting that feeding injury did not reduce root nitrate-N uptake and translocation but may have decreased nitrate-N assimilation into other N compounds. Shoot ureide-N concentration was not different in control or SA-injured plants. Because ureide-N originates from the energy-dependent process of N fixation, we speculate that ureide-N biosynthesis was reduced to an equal extent as dry weight accumulation in SA-injured plants resulting in no concentration change.