Location: Plant Genetics ResearchTitle: Quantitative trait locus mapping for resistance to heat-induced seed degradation and low seed phytic acid in soybean
Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/16/2020
Publication Date: 6/3/2021
Citation: Gillman, J.D., Chebrolu, K., Smith, J.R. 2021. Quantitative trait locus mapping for resistance to heat-induced seed degradation and low seed phytic acid in soybean. Crop Science. 61(3):2023–2035. https://doi.org/10.1002/csc2.20419.
Interpretive Summary: In certain soybean growing regions, elevated temperatures during seed fill can result in poor soybean seed quality and economic losses for producers. We created and tested a genetic mapping population to identify genomic regions that control a unique form of genetic tolerance to the negative impacts of high temperature on soybean seeds. Our population was evaluated in both stress and non-stress field conditions as well as an elevated temperature greenhouse-based experiment. A novel quantitative trait loci (QTL) was found which is associated with superior germination/field emergence, and it was present in multiple experiments. Breeding for more bioavailable phosphorus, which is a target for soybean seed quality improvement, is inextricably linked to reduced germination/field emergence and this effect is exacerbated when seeds develop under elevated temperatures. These finds will inform and guide breeding efforts for abiotic stress tolerance as well as improving soybean seed composition.
Technical Abstract: Soybean [Glycine max (L.) Merr.] reproductive structures are temperature-sensitive, with a reproductive optimum of 22 to 24 °C. Currently, parts of the US soybean growing region experience consistent late-season drought stress, resulting in the adoption of agronomic practices that favor early maturity groups. This approach is the Early Soybean Production System and has boosted yields and on-farm returns on investment. However, seeds produced under this system develop under higher temperatures than standard practices, and frequently have decreased seed quality, loss of value, and unacceptable germination rates. Climate change may result in more widespread lateseason drought and elevated temperatures during seed filling. The ancestors of all modern US high-yielding soybean lines lack substantial resistance to heat-induced seed degradation, but an unadapted plant introduction (PI 587982A) can maintain ~95% quality and germination under the same conditions. Inconsistent germination and emergence defects are associated with increased bioavailable phosphorus and reduced phytic acid. To evaluate these traits’ interaction, a backcross recombinant inbred line population was developed, and emergence and germination were evaluated in seed produced in six greenhouse and field environments. Two mutant alleles (lpa1a and lpa2a) were linked to decreased germination and emergence; this effect was pronounced under elevated temperatures. A novel major-effect heat tolerance quantitative trait locus derived from PI 587982A was identified and found to be associated with positive effects on overall germination and emergence. These results open the potential application of marker-assisted selection for tolerance to elevated temperatures and may accelerate the development of germplasm and cultivars with high-quality seed.