Physiology, mapping population development, and breeding for greater drought tolerance based on carbon and oxygen stable isotope discrimination

1) conduct multi-environment yield tests to determine stability and potential tradeoffs associated with WUE traits,
2) dissect the physiological traits associated with WUE and identify putative genes associated with CID and OID (oxygen isotope discrimination), 3) continue development of mapping populations by advancing the Multi-parent Advanced Generation Inter-Cross (MAGIC) population and inbred line populations, and
4) continue selection and breeding with genotypes with proven isotope signatures and elite varieties
background.

(i) begin to link physiological traits associated with WUE with putative genes underpinning these traits, (ii) advance MAGIC and RIL populations for future genetic mapping efforts, and (iii) conduct yield tests on elite progeny lines under different environments to characterize yield stability and test for potential tradeoffs associated with our target WUE traits.

Updated April 27, 2021:
Water use efficiency (WUE) in crop species is defined as the amount of plant tissue and/or seed yield produced per unit of water used by the crop. Developing soybean varieties with improved drought tolerance can be achieved by increasing
WUE. We previously identified soybean lines that differ in WUE and have been using these lines to improve soybean
drought tolerance. Building on our previous efforts we are now pursuing the following objectives:
1) conduct multi-environment yield tests to determine stability and potential tradeoffs associated with WUE
traits;
2) dissect the physiological traits associated with WUE and identify putative genes associated with carbon isotope discrimination and oxygen isotope discrimination;
3) continue development of mapping populations by advancing the Multi-parent Advanced Generation Inter-Cross (MAGIC) population and inbred line populations that can then be used to identify molecular markers to accelerate breeding; and
4) continue selection and breeding with genotypes with proven isotope signatures (WUE traits) and elite varieties background to develop soybean cultivars that produce more yield per unit of water used.

In 2020, we identified novel genetic markers and confirmed previously identified markers for WUE. We also examined the regions surrounding the markers and have identified a number of candidate genes that may be associated with soybean productivity per unit water.

As part of our breeding effort we have continued to make crosses between elite germplasm and lines selected for WUE traits. Seeds resulting from eight unique crosses have been sent to the winter nursery for generation advancement. Further, we conducted yield tests on the three most promising breeding lines, one of which ranked 5th for yield among all tested lines. Unfortunately, due to travel restrictions associated with COVID-19, we were not able to test yield stability of the three lines across multiple locations.

This project delivers a better understanding of the mechanisms that can be employed to improve soybean yields under drought, germplasm with enhanced WUE, and genetic markers that can be used to accelerate improvement of drought tolerance.

Missouri farmers need soybean varieties capable of producing high yields even under less-than-optimal field conditions. Improving drought tolerance will aid in maintaining yields under reduced water availability and potentially increase yield if water availability is maintained, thus increasing economic returns for Missouri producers.