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This article in CS

  1. Vol. 42 No. 3, p. 739-745
    Received: Sept 1, 2001

    * Corresponding author(s): G.Rebetzke@pi.csiro.au
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Selection for Reduced Carbon Isotope Discrimination Increases Aerial Biomass and Grain Yield of Rainfed Bread Wheat

  1. G. J. Rebetzke *a,
  2. A. G. Condona,
  3. R. A. Richardsa and
  4. G. D. Farquharb
  1. a CSIRO Plant Industry, P.O. Box 1600, Canberra ACT 2601 Australia
    b Australian National Univ., P.O. Box 475, Canberra ACT 2601 Australia


Genetic gain is characteristically slow when selecting directly for increased grain yield under water-limited conditions. Genetic increases in grain yield may be achieved through increases in aerial biomass following selection for greater transpiration efficiency (TE as aerial biomass/water transpired). Strong negative correlations between TE and carbon isotope discrimination (Δ) in wheat (Triticum aestivum L.) suggest that selection of progeny with low Δ may increase TE and aerial biomass under water-limited conditions. This study investigated how early generation, divergent selection for Δ affected aerial biomass and grain yield among 30 low- and 30 high-Δ, ‘Hartog’-like, BC2F4:6 progeny and the recurrent, high-Δ parent Hartog. Lines were evaluated in nine environments varying for seasonal rainfall (235–437 mm) and hence grain yield (1.3–6.2 Mg/ha). Selection for low Δ in early generation progeny was associated with significantly (P < 0.01) smaller Δ, higher grain yield (+5.8%), aerial biomass (+2.7%), harvest index (+3.3%), and kernel size (+4.8%) in tested lines. Kernel number was the same for low- and high-Δ selected groups. Grain yield advantage of the low Δ group increased with reductions in environment mean yield (r = −0.89, P < 0.01) and total seasonal rainfall (r = −0.85, P < 0.01) indicating the benefit of low Δ, and therefore high TE for genetic improvement of grain yield in lower rainfall environments. Narrow-sense heritability on a single-plot basis was much greater for Δ (h 2 = 0.63 ± 0.10) than for either aerial biomass (0.06 ± 0.05) or grain yield (0.14 ± 0.04). Strong genetic correlations between Δ and both aerial biomass (r g = −0.61 ± 0.14) and grain yield (−0.58 ± 0.12) suggest Δ could be used for indirect selection of these traits in early generations. Selection of low Δ (high TE) families for the advanced stages of multiple-environment testing should increase the probability of recovering higher-yielding wheat families for water-limited environments.

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Copyright © 2002. Crop Science Society of AmericaPublished in Crop Sci.42:739–745.