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ARS Home » Southeast Area » Raleigh, North Carolina » Soybean and Nitrogen Fixation Research » Research » Research Project #439233

Research Project: Drought Resiliency for the Farm-Yield Limitations of Commercial Soybean Varieties under Drought (Year 3 of a 3-year project)

Location: Soybean and Nitrogen Fixation Research

Project Number: 6070-21220-069-066-R
Project Type: Reimbursable Cooperative Agreement

Start Date: Oct 1, 2020
End Date: Sep 30, 2021

Objective:
1. Quantify the strengths and weaknesses of current commercial cultivars under drought stress and will draw upon state Official Variety Trials, University Extension specialists, and private breeders to develop entries of commercial varieties for yield testing under rain-fed conditions in North Carolina, South Carolina, Arkansas, Kansas, and Missouri in maturity groups III through VIII. These annual trials will be analyzed and reported in conjunction with state variety trials for farmer use. Based on these results, selections will be made to select the best and worst performing commercial cultivars for follow-up yield trials to more closely examine their drought response in irrigated vs. non-irrigated companion trials, using popular commercial checks for comparison. If a commercial cultivar appears to have superior and stable yield performance under drought, we will engage the developer and attempt to identify the physiological or genetic basis of tolerance. 2. The wealth of advanced drought-tolerant materials from previous United Soybean Board funded pipeline breeding or drought tolerance will be evaluated for yield under drought stress to identify a new generation of breeding stock for the private sector and farmers. The applied breeding pipelines in North Carolina, South Carolina, Arkansas, Missouri, Georgia, and Kansas, have materials ready for yield trials that combine multiple mechanisms of drought tolerance (altered vapor pressure deficit response (VPD), sustained N fixation, fast rooting, and altered hydraulic conductivity in the roots), many of which are reflected morphologically as slow wilting. The breeders will evaluate these new materials using the commercial checks identified in Phase 1 as controls. Conduct basic work to support germplasm development and cultivar release. Also, conduct field-based Quantitative Trait Loci (QTL) mapping, Marker Assisted Backcrossing (MAS), and genome-wide association studies (GWAS) for seed yield, slow wilting, and deep rooting to speed up transfer of these traits to elite cultivars. Physiological investigations will pursue the relationship of field measured water-use efficiency to seed yield under drought. At present, many physiological traits associated with drought tolerance were measured under controlled environment facilities or were indirect surrogates for traits of biological importance. Thus, their connection to yield performance in the field under drought is not fully validated. We will measure instantaneous (intrinsic) water-use efficiency in the field by directly measuring gas exchange and establish its importance by correlating results to yield, slow wilting observations, and other measures of water status.

Approach:
Activity 1a. Commercial varieties will be tested in five states annually. Activity 1b. Analysis of commercial variety performance across locations will begin after multi-state data are collected. Analysis will be updated on an annual basis. Identification of extremes in commercial drought response will begin as sufficient data are collected to make the determinations. Follow up yield testing of extreme commercial material testing will begin under + and – irrigation studies in multiple states. Activity 2a. New breeding lines from five breeding programs will be evaluated for seed yield under drought on an annual basis. Activity 2b. Studies quantifying the impact of slow wilting on seed yield under drought using + and – irrigation regimes will be conducted in five states, annually. Impact of drought and drought tolerance on stability of seed protein content will be investigated in the field annually. Activity 3. Marker Assisted Backcrossing (MAS), genome-wide association studies (GWAS), Quantitative Trait Loci (QTL) mapping, impact of drought and the slow-wilting trait on the stability of seed protein content will be conducted annually. Establishing the relations among photosynthetic activity, leaf water relations, seed yield and the slow-wilting trait will require two summers of drought in the field. Given that the weather cannot be controlled, this will be an annual event.