Phenotyping and quantitative trait locus analysis for the limited transpiration trait in an upper-mid south soybean recombinant inbred line population (“Jackson” × “KS4895”): high throughput aquaporin inhibitor screening

Authors: SARKAR, SAYANTAN - University Of Tennessee; SHEKOOFA, AVAT - University Of Tennessee; MCCLURE, ANGELA - University Of Tennessee; Gillman, Jason

Submitted to: Frontiers in Plant Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/9/2021
Publication Date: 1/20/2022
Citation: Sarkar, S., Shekoofa, A., Mcclure, A., Gillman, J.D. 2022. Phenotyping and quantitative trait locus analysis for the limited transpiration trait in an upper-mid south soybean recombinant inbred line population (“Jackson” × “KS4895”): high throughput aquaporin inhibitor screening. Frontiers in Plant Science. 12. Article 779834. https://doi.org/10.3389/fpls.2021.779834.
DOI: https://doi.org/10.3389/fpls.2021.779834

Interpretive Summary: The vast majority (~90%) of the US soybean crop is grown under rainfed conditions without supplemental irrigation. Irrigation is expensive in terms of infrastructure, fuel for running irrigation pumps and even when fiscally feasible, irrigation may not be unsustainable in the long term due to limited freshwater resources. As a result, drought stress can negatively impact soybean yield and seed quality if of sufficient intensity and/or duration. High yielding soybean lines have experienced a dramatic loss of genetic diversity during the breeding process, and largely do not have substantive tolerance to drought stresses. As a result, there is a strong need to identify and deploy alleles associated with genetic tolerance to drought stress, which has been shown to be present in more genetically diverse but lower yielding and/or less adapted germplasm. In this study, we used a greenhouse-based method to quantify evapotranspiration water losses for a recombinant inbred line population. The resulting data set allowed us to identify genomic regions associated with differential responses (tolerant vs. susceptible) in a recombinant inbred line population, and a number of interesting and potentially useful genomic regions will likely be of interest to physiologists and soybean breeders working to understand and improve the drought tolerance potential of the soybean crop.

Technical Abstract: Soybean is most often grown under rainfed conditions and negatively impacted by drought stress in the upper mid-south of the United States. Therefore, identification of drought-tolerance traits and their corresponding genetic components are required to minimize drought impacts on productivity. Limited transpiration (TRlim) under high vapor pressure deficit (VPD) is one trait that can help conserve soybean water-use during late-season drought. The main research objective was to evaluate a recombinant inbred line (RIL) population, from crossing two mid-south soybean lines (“Jackson” × “KS4895”), using a high-throughput technique with an aquaporin inhibitor, AgNO3, for the TRlim trait. A secondary objective was to undertake a genetic marker/quantitative trait locus (QTL) genetic analysis using the AgNO3 phenotyping results. A set of 122 soybean genotypes (120-RILs and parents) were grown in controlled environments (32/25-d/n °C). The transpiration rate (TR) responses of derooted soybean shoots before and after application of AgNO3 were measured under 37°C and >3.0 kPa VPD. Then, the decrease in transpiration rate (DTR) for each genotype was determined. Based on DTR rate, a diverse group (slow, moderate, and high wilting) of 26 RILs were selected and tested for the whole plant TRs under varying levels of VPD (0.0–4.0 kPa) at 32 and 37°C. The phenotyping results showed that 88% of slow, 50% of moderate, and 11% of high wilting genotypes expressed the TRlim trait at 32°C and 43, 10, and 0% at 37°C, respectively. Genetic mapping with the phenotypic data we collected revealed three QTL across two chromosomes, two associated with TRlim traits and one associated with leaf temperature. Analysis of Gene Ontologies of genes within QTL regions identified several intriguing candidate genes, including one gene that when overexpressed had previously been shown to confer enhanced tolerance to abiotic stress. Collectively these results will inform and guide ongoing efforts to understand how to deploy genetic tolerance for drought stress.