Evaluation location: South Dakota, United States
A total of 334 soybean genotypes including resistant and susceptible checks were screened for resistance to the soybean aphid (SA) in two greenhouse tests in 2011 and spring 2012. Genotypes included 33 from maturity group (MG) 00 and 293 from MG 0, and six resistant and two susceptible checks of later maturity. Each test was replicated three times. All 334 genotypes were evaluated in a greenhouse at South Dakota State University (SDSU) using a caged test and a non-caged test. Greenhouse test plants were inoculated with two, wingless, adult SA from a laboratory colony at SDSU. In the caged test, total SA per plant were counted at 1 wk and at 2 wks after inoculation; in the non-cage test, SA populations were scored by using a 1-to-5 scale at 2 weeks after inoculation (1, <=25 aphids per plant, plant appears normal and healthy; 2 = 26 to 100 aphids per plant, plant appears normal and healthy; 3 = 101 to 200 aphids per plant, older leaves may be slightly yellowing; 4 = 201 to 500 aphids per plant, plant appears slightly stunted with yellowing of older leaves and minor curling of young leaves, and slight appearance of sooty mold on stem and leaves; 5, > 500 aphids per plant, often with obvious symptoms on foliage such as leaf curling, yellowing and sooty mold development). Four genotypes (PI 430491, PI 464911, PI 603432B, and PI 603712) were resistant, and three genotypes (PI 612759B, PI 200595, and PI 603426D) were moderately resistant. Five of six resistant control lines (PI 71506, PI 243540, PI 567541B, PI 567543C, and PI 567597C) were resistant, but PI 548663 was susceptible. All other lines were susceptible.