Evaluation location: Georgia, United States
To evaluate resistance to Heterodera glycines, five seeds of each cultivar were planted in 420-ml styrofoam cups filled with soil naturally infested with either race 3 or race 14 (7). The soil infested with race 3 (cyst index: Peking, 0; Pickett, 1; P188788, 0; P190763, 0) was a Cecil coarse sandy loam (72% sand, 12% silt, 16% clay; a member of the clayey, kaolinitic, thermic family of Typic Hapludults) collected from the Plant Sciences Farm near Athens, Georgia. The soil infested with race 14 (cyst index: Peking, 37; Pickett, 76; PI 88788, 1; PI 90763, 11) was a Dothan sandy loam (85% sand, 12% silt, 3% clay; a member of the fine-loamy, siliceous, thermic family of Plinthic Paleudults) collected near Waynesboro, Georgia. One week after planting, seedlings were thinned to one per cup and watered as needed. After 30-40 days, when white females and cysts had developed on susceptible standard cultivars, the soil was gently shaken from each root system, white females and cysts were enumerated under a magnifying lamp, and a resistant or susceptible rating was assigned. Plants were assigned a rating of susceptible (generally >or = 11 white females or cysts per plant) or resistant (generally < or = 10 white females or cysts) on the basis of number of white females or cysts relative to the standard resistant cultivars. The resistant and susceptible standards were Centennial and Lee for race 3 and Leflore and Centennial for race 14, respectively. Each cultivar was evaluated a minimum of 2 years in a randomized complete block experimental design with four replications. Plants were grown with supplemental light provided by 400-W metal halide lamps and fertilized weekly with 6 mg N, 3 mg P, and 5 mg K.