Influence of previous infestation of soybean on the soybean aphid, Aphis glycines Matsumura (Hemiptera: Aphididae)

The soybean aphid, Aphis glycines Matsumura, first detected in the US in 2000 (Ostlie, 2002; Alleman et al. 2002) is a major pest of soybean. It has already evolved a new biotype (Ohio biotype) which is virulent to the Rag1 gene that confers resistance to soybean against the original Illinois biotype (Kim et al. 2008). This plant resistance study aims to achieve an understanding of induced resistance in soybean genotypes as a result of previous infestation by soybean aphids. Preliminary experiments with the genotypes K1621 and K1639 and the susceptible checks KS4202 and KO3-4686, exposed to 10 aphids for 2 days, suggested an induction of antibiotic resistance against the aphid (Illinois biotype) in all except KO3-4686. However, no significant induction of resistance affecting the reproductive performance of the aphid was observed in the same genotypes upon preconditioning with 10 aphids (Illinois biotype) over a range of time viz., 2, 4, 9 and 12 days respectively. Soybean genotypes like EO6902, EO7906-2 developed in MSU and some PIs have been found to be resistant to the Ohio biotype of the soybean aphid and currently, experiments are underway to study the effect of induced resistance on this biotype. The Electrical Penetration Graph (EPG) technique will give further insight on the effect of induced resistance, if any, on the feeding behavior of the soybean aphid.