Effect of temperature and water deficit on water-use efficiency, carbon isotope discrimination, and specific leaf area in peanut

Carbon isotope discrimination (Delta) and specific leaf area (SLA) have bee n shown to be correlated with water-use efficiency (WUE) of peanut (Arachis hypogaea L.) and SLA has been proposed as an indirect selection criterion for Delta and WUE. The effect of high temperature and water deficit on WUE, Delta, and SLA, and relations between them, was investigated in controlled environments. Five Spanish (A. hypogaea ssp.fastigiata) and three Virginia (A. hypogaea csp. hypogaea, botanical type) lines were grown at mean tempe ratures of 27 and 34 degrees C and at 50 and 100% available soil water (ASW ) from first flowering to maturity, and WUE, Delta, and SLA measured at mat urity. Virginia genotypes had higher total dry matter, water use and WUE (P less than or equal to 0.01), but were more sensitive to high temperature ( P less than or equal to 0.01) than Spanish genotypes. Water deficit reduced water use and SLA, and increased WUE, The only water deficit x temperature interaction (P < 0.05) was for Delta, where water deficit reduced the valu e of Delta at 27 degrees but not at 34 degrees C. High temperature had no e ffect on water use, but decreased WUE and increased SLA, Across all Hater d eficit and temperature treatments (n = 32), WUE was correlated with Delta ( r = -0.78, P < 0.001) and SLA (r = -0.70, P < 0.001), and SLA correlated wi th Delta (r = 0.75, P < 0.001) with no difference associated with botanical type. Temperature and water deficit had significant (P less than or equal to 0.05) effects on the intercept, but not the slope of these relations. Th e results support the view that SLA can be used as an indirect selection cr iterion for Delta and WUE in genotypic selection.