Metabolite and Fatty Acid Levels Associated With Pod Yield Under Drought Stress in Peanut.

The Virginia-Carolina (VC) region including Virginia, North Carolina, and South Carolina, is the most important peanut production region for the large-seeded, virginia-type peanut in the United States.  In recent years, an increased frequency of drought and heat episodes was observed in the VC-region. Because limited information is available on the mechanisms virginia-type peanut develops in target environments response to drought stress, the present study evaluated several physiological and metabolic characteristics and their relationship with yield for eight cultivars and breeding lines. Experiments were conducted under rainfed and irrigated field trials in 2011 and 2012.  The long term goal of this study was to identify drought tolerant peanut lines in the VC-region.  Visible symptoms of drought stress were observed in peanut during the field experiments in both years.  Significant (p ≤ 0.05) variations for yield, membrane injury, chlorophyll fluorescence (F_v/F_m ratio), specific leaf area, SPAD chlorophyll content, and relative levels of metabolites and fatty acids were observed in response to water regime, growth stage, and genotype in both years during the field studies.  Similarly each year, the F_v/F_m ratio, organic acids, and saturated fatty acids decreased in rainfed vs. irrigated plants, while the sugar and sugar alcohol relative levels increased.  Regardless of the water regime, lower levels of saturated fatty acids and sugars, and higher levels of unsaturated fatty acids and sugar alcohols were associated (p < 0.05) with higher pod yield in field conditions.  A general decrease in organic acid and saturated fatty acid levels and an increase in membrane injury, sugar, and unsaturated fatty acid levels were observed.  Among eight genotypes, SPT 06-07 showed improved tolerance to both stresses. Overall, results from this study were suggestive of natural stress responses rather than adaptive mechanisms to drought of the virginia-type cultivars and breeding lines used in this study.