BACKCROSSING HIGH SEED PROTEIN TO A SOYBEAN CULTIVAR

An inverse relationship between seed yield and seed protein concentrat ion has limited success in developing soybean [Glycine mar (L.) Merr.] cultivars with high seed protein. High protein from the donor parent 'Pando' (498 g kg(-1) protein) was backcrossed to 'Cutler 71' (408 g k g(-1) protein) to determine if the yield of Cutler 71 could be recover ed in addition to the high protein from Pando. Random F-4-derived line s, plus three Lines with highest seed protein concentration, from the initial cross, the BC1, and the BC2 populations, were evaluated for ag ronomic traits in separate, two-replicate tests for 1 yr at West Lafay ette, IN. Seed from replication composites were evaluated for protein and oil concentration using near infra-red reflectance or near infra-r ed transmission. The parent line for each backcross was selected first for high seed protein, then for yield and agronomic similarity to Cut ler 71. Random F-4-derived progenies of the BC3 population, the parent line for each backcross, and the cultivars Pando, Cutler 71, and Hami lton were evaluated in three-replicate tests for 2 yr at West Lafayett e, IN. In each backcross generation, lines were identified with seed p rotein in excess of 470 g kg(-1) and that progressively approached the yield of Cutler 71. In the BC3 population, one Line averaged 472 g kg (-1) seed protein and was significantly (P = 0.05) higher in seed yiel d than Cutler 71, similar in yield to the cultivar Hamilton. In each b ackcross population, there were inverse relationships between seed yie ld and seed protein (R(2) values ranging from 0.33 to 0.06) and betwee n seed protein and seed oil (R(2) values ranging from 0.55 in BC1 to 0 .94 in BC3). In successive backcross populations, minimum oil values i ncreased from 148 in BC1 to 174 g kg(-1) In BC3, indicating a trend to ward recovering oil concentration (204 g kg(-1)) of Cutler 71. The dat a demonstrate that high seed protein can be backcrossed to a soybean c ultivar, fully recovering the seed yield of the cultivar, suggesting t he absence of physiological barriers to combining high seed protein wi th high seed yield in these populations.