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Does Maintaining Green Leaf Area in Sorghum Improve Yield under Drought? II. Dry Matter Production and Yield


This article in CS

  1. Vol. 40 No. 4, p. 1037-1048
    Received: May 24, 1999

    * Corresponding author(s): borrela@dpi.qld.gov.au
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  1. Andrew K. Borrell *a,
  2. Graeme L. Hammerb and
  3. Robert G. Henzella
  1. a Hermitage Research Station, Department of Primary Industries, Warwick Queensland 4370, Australia
    b QDPI/CSIRO Agricultural Production Systems Research Unit, Toowoomba Queensland 4350, Australia


Retention of green leaf area at maturity (GLAM), known as stay-green, is used as an indicator of postanthesis drought resistance in sorghum [Sorghum bicolor (L.) Moench] breeding programs in the USA and Australia. The critical issue is whether maintaining green leaves under postanthesis drought increases grain yield in stay-green compared with senescent hybrids. Field studies were undertaken in northeastern Australia on a cracking and self-mulching gray clay. Nine closely related hybrids varying in rate of leaf senescence were grown under two water-limiting regimes, post-flowering water deficit and terminal (pre- and postflowering) water deficit, and a fully irrigated control. Under terminal water deficit, grain yield was correlated positively with GLAM ( r = 0.75** ) and negatively with rate of leaf senescence ( r = −0.74** ) Grain yield also increased by ≈0.35 Mg ha−1 for every day that onset of leaf senescence was delayed beyond 76 DAE in the water-limited treatments. Stay-green hybrids produced 47% more postanthesis biomass than their senescent counterparts (920 vs. 624 g m−2) under the terminal water deficit regime. No differences in grain yield were found among eight of the nine hybrids under fully irrigated conditions, suggesting that the stay-green trait did not constrain yield in the well-watered control. The results indicate that sorghum hybrids possessing the stay-green trait have a significant yield advantage under postanthesis drought compared with hybrids not possessing this trait.

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