The purpose of this research project is to provide Year 2 funding for the University of Tennessee Soybean Breeding & Genetics Program for the development of high yielding soybean cultivars with adaptation to Tennessee and the Mid-South region that contain the indeterminate growth habit. We intend to use the Dt1 growth habit molecular marker to aid our efforts in achieving this goal, following a molecular back-crossing introgression approach.

Research suggests that indeterminate soybean varieties have a greater potential for high yield and resistance to drought. This can be illustrated by the shift in maturity for soybean varieties planted in the Mid-South, with greater emphasis in recent years on earlier maturing varieties that are more likely to have indeterminate growth. As far incomes benefit from having the greatest possible yield using the fewest possible inputs, having elite soybean varieties with indeterminate growth would help achieve this outcome by allowing for high yield potential with less water input needed. This could provide farmers a much needed security, as irrigation is a costly and limited resource. This project will demonstrate the feasibility of converting a determinate variety to an indeterminate variety using molecular trait introgression.

Our objective for this project is to send each of the three recurrent parents and corresponding hybrid seeds to winter nursery to continue the back crossing process. Donor plants would be screened with molecular markers for the Dt1 locus to ensure that the back crosses would contain the allele controlling indeterminate growth. Once identified, these indeterminate donors would be crossed with the recurrent parents, resulting in BC2F1 seed (87.5% recurrent parent).

The long term goal of this project would be to continue back crossing using the methods described above until BC3 (94% recurrent parent) or BC4 (97% recurrent parent) generation, and identify indeterminate breeding lines with excellent agronomic characteristics for yield testing and eventual cultivar release. This would provide Tennessee soybean producers with highly productive indeterminate cultivars with elite agronomic characteristics and ability to withstand drought. Simultaneous with this approach new forward and back crosses will continue in order to provide adapted indeterminate soybean varieties for Tennessee and Mid-South region.