JXB Advance Access published online on August 13, 2008
Journal of Experimental Botany, doi:10.1093/jxb/ern199
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© 2008 The Author(s).
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/2.0/uk/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
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RESEARCH PAPER |
Different mechanisms of adaptation to cyclic water stress in two South Australian bread wheat cultivars


1Australian Centre for Plant Functional Genomics, Waite Campus, The University of Adelaide, PMB1, Glen Osmond, SA 5064, Australia
2Division of Plant Industry, CSIRO, GPO Box 1600, Canberra, A.C.T. 2601, Australia
To whom correspondence should be addressed. E-mail: mark.tester{at}acpfg.com.au
In the South Australian wheat belt, cyclic drought is a frequent event represented by intermittent periods of rainfall which can occur around anthesis and post-anthesis in wheat. Three South Australian bread wheat (Triticum aestivum L.) cultivars, Excalibur, Kukri, and RAC875, were evaluated in one greenhouse and two growth-room experiments. In the first growth-room experiment, where plants were subjected to severe cyclic water-limiting conditions, RAC875 and Excalibur (drought-tolerant) showed significantly higher grain yield under cyclic water availability compared to Kukri (drought-susceptible), producing 44% and 18% more grain compared to Kukri, respectively. In the second growth-room experiment, where plants were subjected to a milder drought stress, the differences between cultivars were less pronounced, with only RAC875 showing significantly higher grain yield under the cyclic water treatment. Grain number per spike and the percentage of aborted tillers were the major components that affected yield under cyclic water stress. Excalibur and RAC875 adopted different morpho-physiological traits and mechanisms to reduce water stress. Excalibur was most responsive to cyclic water availability and showed the highest level of osmotic adjustment (OA), high stomatal conductance, lowest ABA content, and rapid recovery from stress under cyclic water stress. RAC875 was more conservative and restrained, with moderate OA, high leaf waxiness, high chlorophyll content, and slower recovery from stress. Within this germplasm, the capacity for osmotic adjustment was the main physiological attribute associated with tolerance under cyclic water stress which enabled plants to recover from water deficit.
Key words: Cyclic drought, osmotic adjustment, wheat
* Present address: Department of Agronomy and Plant breeding, Faculty of Agriculture, The University of Birjand, Birjand, Iran.
Present address: Leibniz-Institute of Plant Genetics and Crop Plant Research (IPK), Corrensstr. 3, D-06466 Gatersleben, Germany.
Received 30 April 2008; Accepted 23 June 2008