Location: Plant Physiology and Genetics Research
Project Number: 2020-21000-013-02-R
Project Type: Reimbursable Cooperative Agreement
Start Date: Oct 1, 2017
End Date: Sep 30, 2018
A perceived weakening of the United States regulatory framework is causing end users to lower confidence in the sustainability of United States soy. A primary constraint on United States soybean sustainability is the widely fluctuating yields due to drought. We have recently discovered maturity group (MG) 4 soybean genotypes from the germplasm collection that wilt more slowly, have higher water use efficiency (WUE), have cooler canopy temperatures, and fix larger amounts of nitrogen than any germplasm previously discovered. Additionally, we have discovered molecular markers associated with multiple genes. In this research, we will evaluate the utility of these molecular markers in improving drought tolerance, determine the stability of these traits across extremely different environments, and pyramid favorable genes for each trait as well as stack these traits into improved germplasm lines for release. This proposal brings together a diverse group of scientists from the University of Arkansas, the University of Missouri, and the USDA-ARS labs at Columbia, MO, Maricopa, AZ and Stoneville, MS to leverage the discoveries from previous research by confirming the benefits of targeted traits for improving drought tolerance and providing a roadmap for utilizing the alleles for these four traits (Canopy temperature (CT) and wilting (CW), Water use efficiency (WUE), and nitrogen derived from the atmosphere (NDFA)) to enhance drought tolerance in improved soybean germplasm. Our specific objectives are: Objective 1: Physiological Mechanisms of drought tolerance. Determine trait stability over multiple environments in well-watered and rain-fed/dryland conditions and dissect mechanisms underlying the target traits. Objective 2: Identification and confirmations of putative drought tolerance loci. Confirm the potential of drought tolerance/trait markers previously identified by genome wide association (GWAS) studies. Map and confirm putative quantitative trait loci (QTLs) in specific bi-parental mapping populations. Objective 3: Germplasm and population development. Develop and evaluate germplasm with multiple traits (stacking CW, CT, WUE, and NDFA) and/or multiple genomic loci for each trait (pyramid loci).
The research proposal will include collaborative efforts among the Co-PIs. Below are the ARS Maricopa experimental approaches: Objective 1: Physiological Mechanisms of drought tolerance: The field study will include a soybean diversity panel consisting of 200 strategically selected genotypes that will be grown at four locations (AR, MO, MS and AZ) under well-watered and drought stress conditions. At each location, accessions will be planted in randomized complete block design (RCBD) (or augmented lattice design) with 3 replicates each. We will collect data on CT, CW, WUE, and NDFA. Canopy wilting will be scored on a scale from 0 (no wilting) to 100 (severe wilting with dying plants) as we have done previously. Canopy temperature will be determined from aerial infrared (IR) images using a small unmanned aerial system at Arkansas location. At Maricopa, CT will be measured using Apogee SI-131 infrared thermometers mounted on LeeAgra AvengerPro fully customized hydrostatic spray vehicle. For WUE, we will collect 4 to 5 plants when plants are between R1 and R2 for 13C isotope analysis. The same plant material will also be used for 15N analysis. Static and dynamic stability values will be calculated and analyzed using mixed models for each location and over locations using mixed models of SAS package. Objective 2: Identification and confirmations of putative drought tolerance loci. 200 soybean accessions with high and low breeding values for CT, CW, WUE, NDFA have been ordered from the germplasm collection and will be increased in 2017 at Fayetteville, AR. In 2018, we propose to evaluate these accessions in side-by-side irrigated and drought stressed environments at Pine Tree and Rohwer, Arkansas, Portageville, Missouri, and Maricopa, Arizona. Data will be analyzed for each location separately and over locations to estimate best linear unbiased predictors (BLUPs) of each phenotypic trait using mixed models of statistical analysis software (SAS) package. Association between genotypic and phenotypic data will be calculated using the Fixed and random model Circulating Probability Unification (FarmCPU) model. Objective 3: Germplasm and population development: In the proposed research, up to 10 F6:8 lines with high WUE and 10 with low WUE (all with high germinability trait) will be harvested in Mississippi in 2017. We will initiate irrigated yield trials of these 20 lines in 2018 (MS) coupled with WUE measures and seed quality traits (germination, protein, oil, etc.). Seed harvested from the 2018 trials will then be used in irrigated and non-irrigated comparative trials beginning in 2019 (AR, AZ, MO, and MS). The Maricopa, AZ location provides an ideal environment to evaluate the combination of drought and high temperature stresses in comparison to high temperature stress in the absence of drought (i.e., irrigated treatment). The best yielding, most WUE lines, will be identified for release. These releases will mostly be maturity group (MG) IV lines. Extreme lines may be targeted for more intense physiological evaluations.