Metabolic and Physiological Responses to Water Deficit Stress of Eight Virginia-Type Peanut (Arachis hypogaea L.) Cultivars and Breeding Lines.

Variability to water-deficit stress responses in peanut may be related to differential metabolic changes associated with the stress. The objective of this study was to identify metabolites associated with the physiological characteristics developed by eight peanut genotypes in response to water-deficit stress under field conditions. Eight Virginia type peanut cultivars and breeding lines were grown under rainfed (water-deficit) and irrigated field plots at Tidewater Agricultural Research and Extension Center in Suffolk, VA, during the 2011 and 2012 growing seasons. Physiological responses to water-deficit stress were evaluated by the maximum fluorescence yield measured as ratio of variable (Fv) vs. maximum (Fm) chlorophyll fluorescence (Fv/Fm), and plasma membrane injury measured by the electrolyte leakage method. Metabolites analyzed using gas chromatography-mass spectrometry based methods included sugars, sugar alcohols, and organic acids. Measurements were performed at the beginning flowering (R1), beginning pod (R3), and beginning seed (R5) peanut growth stages. The Fv/Fm ratio was significantly reduced by water-deficit stress at R1. At the same growth stage, membrane injury was 20% higher in water-deficit vs. irrigated plants. At R3, no difference was observed for the Fv/Fm ratio between water-deficit and irrigated plants. In contrast to R1, at R5 the irrigated plants had greater decline in the Fv/Fm ratio and higher membrane injury in comparison with water-deficit plants, suggesting acclimation processes induced by water-deficit stress at earlier growth stages. Major metabolites associated with these responses included organic acids (succinate and phosphate), sugars (fructose, sucrose and glucose) and sugar alcohols (inositol and pinitol).