Assessing Michigan-bred soybean lines for resistance to the soybean aphid (Aphis glycines), and defoliation by the Japanese beetle Popillia japonica

Enhancing soybean germplasm by incorporating resistance to the soybean aphid,Aphis glycines Matsumura, (Hempitera: Aphididae) is important to reduce yield loss and insecticide costs for soybean production in the North Central States. Resistance to soybean aphid (SBA) was screened in three aphid-resistant lines developed by the MSU Soybean Breeding Program (E06901, E06905, E06906) compared to a commercial susceptible variety. Resistant and commercial lines were planted in replicated plots in two locations in MI. Weekly sampling for SBA using whole-plant counts indicated, fewer SBA abundance and lower infestations on resistant lines. Under no-choice conditions using plants infested then caged, resistant lines had lower SBA density than the susceptible line under pressure of natural enemies. In caged plants,when total SBA-abundance/plant after two weeks were counted,both nymphs and adults reproduced less on resistant lines. Within each resistant line, SBA numbers were significantly different between caged and open plants. Clip-cage experiments were conducted, to determine differences in SBA survival, fecundity and longevity on resistant and susceptible lines by restricting individual aphids (1-d-old viviparous aptera) to clip-cages in low, mid and, high positions of a plant. Leaf damage caused by Popillia japonica was assessed on these lines during out-breaks. Results of this study will assist the university Soybean Program, to further enhance these lines as aphid-resistant cultivars suitable for commercial release.