Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 10, 2011
Publication Date: October 4, 2011
Citation: Ries, L.L., Purcell, L.C., Carter Jr, T.E., Edwards, J.T., King, C.A. 2011. Physiological traits contributing to differential canopy wilting in soybean under drought. Crop Science. Vol. 52. pp. 272-281.
Interpretive Summary: The slow wilting genetic trait in soybean is important because it confers agronomic levels of drought tolerance to the crop, perhaps 5 to 8 bu/ac under drought conditions. Although the trait is important and being used in soybean breeding, the trait is poorly understood mechanistically. That is, we do not fully understand how this trait works. If we understood the trait better, then it would be easier for the plant breeder to use, and it would make its way to the farmer’s field faster. This study examines hypotheses related to the underlying control mechanism. It turns out that the control mechanism is not simple and may involve more than one strategy for imparting crop protection under drought conditions.
Delayed wilting is observed in a few unusual soybean genotypes, but the underlying physiological control mechanisms are poorly understood. We hypothesized that soybean genotypes with delayed wilting conserve soil moisture by restricting transpiration and that this would be reflected in decreased radiation use efficiency (RUE) and/or improved water use efficiency (WUE). This strategy would conserve soil moisture when it is plentiful so that it would be available when needed later in the season. Irrigated field experiments in 8 environments compared RUE of genotypes known to wilt differently during drought. Slow-wilting genotypes generally had lower RUE than fast-wilting genotypes, consistent with our hypothesis. Three of four slow wilting genotypes had higher soil moisture immediately prior to irrigation than fast-wilting genotypes, which is also consistent with the hypothesis. Genotypic differences in carbon isotope discrimination (CID, a proxy for WUE) were present but were not consistently related with slow wilting. Results suggest that multiple mechanisms involving RUE and WUE could result in soil-water conservation in these diverse genotypes.