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  1. Vol. 34 No. 1, p. 92-97
     
    Received: Aug 31, 1992
    Published: Jan, 1994


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doi:10.2135/cropsci1994.0011183X003400010016x

Water-Use Efficiency and Carbon Isotope Discrimination in Peanut under Water Deficit Conditions

  1. G. C. Wright,
  2. R. C. Nageswara Rao  and
  3. G. D. Farquhar
  1. Q ueensland Dep. Primary Ind., PO Box 23, Kingaroy, Q 4610
    C rop Physiology, Legumes Program, ICRISAT, Patancheru 502 324, A.P., India

Abstract

Abstract

Because of its relationship with water-use efficiency (W), carbon isotope discrimination in leaves (Δ) was proposed to be useful for identifying genotypes with greater water-use efficiency. In this study we examined the relationship between W and Δ in four peanut (Arachis hypogaea L.) genotypes. The genotypes were grown in and around mini-lysimeters embedded in soil and were subjected to two drought regimes, intermittent and prolonged water deficit conditions, by varying the irrigation timing and amount. Automated rain-out shelters prevented any rain from reaching the experimental plots during the treatment period. The mini-lysimeters allowed accurate measurement of water use and total dry matter (including roots) in a canopy environment. Water-use efficiency, which ranged from 1.81 to 3.15 g kg−1, was negatively correlated with Δ, which ranged from 19.1 to 21.8%. Tifton-8 had the highest W (3.15 g kg−1) and Chico the lowest (1.81 g kg−1, representing a variation in W of 74% among genotypes. Variation in W arose mainly from genotypic differences in total dry matter production rather than from differences in water use. It is concluded that δ is a useful trait for selecting genotypes of peanut with improved W under drought conditions in the field. A strong negative relationship existed between W and specific leaf area (SLA, cm3 g−1) and between Δ and SLA, indicating that genotypes with thicker leaves had greater W. SLA could therefore be used as a rapid and inexpensive selection index for high W in peanut where mass spectrometry facilities are not available.

Submitted as ICRISAT Journal Article no. 1389.

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