Variabilities in symbiotic nitrogen fixation and carbon isotope discrimination among peanut (Arachis hypogaea L.) genotypes under drought stress

Authors: XU, WANG - Auburn University; CHEN, CHARLES - Auburn University; Dang, Phat; CARTER, JOSHUA - Auburn University; ZHAO, SHULI - Auburn University; Lamb, Marshall; CHU, YE - University Of Georgia; Holbrook, Carl - Corley; OZIAS-AKINS, PEGGY - University Of Georgia; ISLEIB, THOMAS - North Carolina State University; FENG, YUCHENG - Auburn University

Submitted to: Journal of Agronomy and Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/8/2022
Publication Date: 7/29/2022
Citation: Xu, W., Chen, C., Dang, P.M., Carter, J., Zhao, S., Lamb, M.C., Chu, Y., Holbrook Jr, C.C., Ozias-Akins, P., Isleib, T., Feng, Y. 2022. Variabilities in symbiotic nitrogen fixation and carbon isotope discrimination among peanut (Arachis hypogaea L.) genotypes under drought stress. Journal of Agronomy and Crop Science. 1–14. https://doi.org/10.1111/jac.12619.
DOI: https://doi.org/10.1111/jac.12619

Interpretive Summary: Drought stress is one of the major environmental factors limiting peanut productivity. The vulnerability of peanut to drought varies depending on genetic potential, crop growth stages, and environmental conditions. The objective of this study was to evaluate the effects of drought stress on the capacity of peanut to fix nitrogen and to efficiently grow by the assimilation of carbon among different peanut lines. Two parental lines and 14 siblings resulting from a particular cross with varying drought tolerance characteristics were evaluated in environmentally controlled shelters testing middle-season drought, late-season drought, and full watering control throughout season. Nitrogen fixation and carbon assimilation capacity were measured for two growing seasons. Reduction of shoot nitrogen fixation for drought treatment was observed for both seasons, with a greater reduction in middle-season drought compared to late-season drought. Middle-season drought reduced carbon assimilation in both years but did not change significantly in late-season drought. Reduction for nitrogen fixation and carbon isotope discrimination were more severe in drought susceptible lines compare to more drought tolerant lines, especially for middle-season drought compared to late-season drought. Additionally, reduction in nitrogen fixation capacity did not return to pre-drought levels suggesting that drought resulted in a lasting damage. Our data suggested that unlike other traits, nitrogen fixation in many peanut lines may not recover from the damage caused by drought upon re-watering. Information from this research will facilitate the identification of drought tolerant lines with the potential to maintain high nitrogen fixation and carbon assimilation capacity.

Technical Abstract: Drought stress is one of the major environmental factors limiting peanut (Arachis hypogea L.) productivity. The vulnerability of peanut to drought varies depending on genotypic characteristics, crop growth stages, and environmental conditions. The objective of this study was to evaluate the effects of drought stress on symbiotic nitrogen fixation and carbon isotope discrimination in various peanut genotypes. Two parental lines and 14 recombinant inbred lines with varying drought tolerance characteristics were evaluated in rainout shelters under three irrigation regimes: irrigated control, middle-season drought with rehydration, and late-season drought with rehydration. Symbiotic nitrogen fixation capacity and carbon isotope discrimination in different genotypes were evaluated by measuring 15N and 13C natural abundance, respectively, for two years. Reduction in percentages of shoot N derived from the atmosphere (%Ndfa) was observed under both drought treatments in both years; a greater reduction was observed under middle-season drought than under late-season drought. Middle-season drought negatively affected carbon isotope discrimination in both years although no significant difference was observed under late-season drought. Variabilities in %Ndfa and carbon isotope discrimination were found among different genotypes. Under middle-season drought, both %Ndfa and carbon isotope discrimination were higher in drought tolerant lines than drought susceptible lines, and the most drought tolerant lines had the highest N-fixing capacity under both drought treatments in the study periods. Additionally, there was a positive correlation between %Ndfa and carbon isotope discrimination under both drought treatments. In most genotypes, %Ndfa remained unchanged after rehydration; only a few genotypes showed a slight increase in %Ndfa after rehydration following middle-season or late-season drought. Our data suggested that unlike other traits, symbiotic nitrogen fixation in many peanut genotypes were negatively affected by drought and may not recover from the damage caused by drought upon rehydration.