Resistance to Aphis glycines among wild soybean accessions in laboratory experiments

The soybean aphid (Aphis glycines Matsumura) is a major pest of soybean (Glycine max (L.) Merr.) in eastern Asia and in North America. Aphid-resistant soybean cultivars have been developed as a non-chemical management tactic, but viability of this tactic may depend on the availability of diverse resistance sources, including wild soybean (Glycine soja Siebold and Zucc.), in order to counter various resistance-breaking soybean aphid biotypes. In this study, 10 wild soybean accessions were identified as resistant in free-choice screening assays against avirulent soybean aphid biotype 1, and eight of the accessions were advanced for follow-up in two, 20-day-long no-choice assays. Two accessions, PI 65549 and PI 135624, did not differ from resistant check PI 549046 in number of aphids per plant after 10 and 20 days of infestation; accessions 99PI101404B, PI 549035 B, and PI 342618 A had more aphids than PI 549046 by day 20, but fewer aphids than known susceptible accessions. In a second no-choice assay, accessions 99PI81762 and PI 101404 A had fewer aphids than other test accessions but more aphids than PI 549046 by day 20. Because of particularly strong resistance in PI 135624 and PI 65549, these two accessions should be genetically characterized and tested for resistance against virulent soybean aphid biotypes.