Water availability across U.S. peanut (Arachis hypogaea L.) producing areas is becoming threatened due to years of drought and competing urban demands. High water-use efficiency (WUE) has now become a priority in many peanut breeding programs. To support this effort, the variation in WUE, as measured by carbon isotope composition (d13C), of up to 19 cultivars was evaluated in Alabama, Georgia, Florida, New Mexico, North Carolina, Oklahoma and Texas. Additionally, the variation in d15N, percent carbon and nitrogen, SPAD chlorophyll content and specific leaf area corrected for solar radiation and VPD (SLARV) was determined. SLARV and SPAD chlorophyll were correlated with carbon isotope composition (d13C) to determine if these inexpensive measurements could be used as selection tools for WUE in breeding programs. For genotypes measured at several sites simultaneously, genetic, environmental, and genotype X environment interactions were found to significantly affect most traits. Variation among genotypes grown at single sites was also found for measured traits. Genotypes were ranked within each site according to d13C. Lastly, SLARV, SPAD, and d13C were correlated, but the significance and direction of the correlation was highly variable within regions and years making the use of these measurements for surrogates of WUE in U.S. breeding programs limited.
Key words: Water-use efficiency, carbon isotope, nitrogen isotope, drought.
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