Resistance to soybean aphid in early maturing soybean germplasm

Since 2000, the soybean aphid (Aphis glycines Matsumura) has become a major pest of soybean [Glycine mar (L.) Merr.] in North America. In the USA, there are currently no commercial soybean cultivars with aphid resistance and there are no reported resistance sources in early maturing soybean germplasm. The objectives of this study were to identify sources and types of resistance to soybean aphid from early maturing soybean germplasm. Over a 2-yr period, 2147 soybean accessions from maturity group (MG) 0 to 111, originally from northern China, were evaluated for aphid resistance in a greenhouse and in field cages. The plants were hand-inoculated and aphid populations were evaluated 10 d after inoculation. A damage index (0-100%) was calculated for each accession. After 2 yr of evaluation and confirmation in choice tests, four MG III accessions from Shandong province, PI 567543C, PI 567597C, PI 56754113, and PI 56759813, were found to be resistant to the soybean aphid. Two of these accessions, PI 567541B and PI 567598B, possessed antibiosis resistance, preventing the aphids from reproducing on the plants in a no-choice study. PI 567543C and PI 567597C possessed amixenosis resistance. These resistant sources can be used to develop commercial cultivars with aphid resistance for the North Central states.