Genetic Introgression from Glycine tomentella to Soybean to Increase Seed Yield.

Soybean [Glycine max (L.) Merr.] breeding in the U.S. currently relies on a narrow genetic base in which more than half of the genetic contribution, calculated by pedigree analysis, comes from only 5 ancestral lines. For decades, but more intensely in recent years, efforts have been made to incorporate exotic soybean germplasm into the breeding pool. Glycine tomentella, native to Australia, is a perennial relative in the tertiary gene pool of soybean. Although G. tomentella has been shown to have high levels of resistance to several diseases, including soybean rust and soybean cyst nematode, no effort has been devoted to utilizing this species to increase the genetic yield potential of soybean. The objectives of this research are to identify high yielding lines derived from backcrosses between the cultivar Dwight and G. tomentella PI 441001 (2n=78), and to determine the genetic contribution of PI 441001 to these lines. PI 441001 was crossed to Dwight and immature seed rescue was used to produce a sterile F₁ plant. Amphidiploid plants (2n=118) were produced by treating the F₁ hybrid with colchicine. Amphidiploid plants were backcrossed to Dwight to obtain BC₁ plants. A series of backcrosses were made with eight different BC₂ plants to obtain BC₃, BC₄, BC₅ and BC₆ lines with 2n=40 chromosomes. Preliminary yield testing of inbred lines from these crosses was used to select 180 lines in maturity groups (MG) II, III and IV. Yield data were collected in two replication tests at six to eight locations in Ohio, Illinois, Missouri and Nebraska in 2013 and 2014. These data identified experimental lines in all three MGs that are significantly higher yielding than the recurrent parent. All experimental and parental lines were genotyped using genotyping by sequencing. G. tomentella introgressions will be tested for associations with yield, maturity, height and lodging.