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Plant function and evolutionary biology
RESEARCH ARTICLE (Open Access)

Impact of ancestral wheat sodium exclusion genes Nax1 and Nax2 on grain yield of durum wheat on saline soils

Richard A. James A F , Carol Blake A , Alexander B. Zwart B , Ray A. Hare C , Anthony J. Rathjen D and Rana Munns A E
+ Author Affiliations
- Author Affiliations

A CSIRO Plant Industry, GPO Box 1600, Canberra, ACT 2601, Australia.

B CSIRO Mathematics, Information and Statistics, GPO Box 664, Canberra, ACT 2601, Australia.

C NSW Department of Primary Industries, RMB 944, Tamworth, NSW 2340, Australia.

D University of Adelaide, Waite Campus, Glen Osmond, SA 5064, Australia.

E School of Plant Biology, University of Western Australia, Crawley, WA 6009, Australia.

F Corresponding author. Email: richard.james@csiro.au

Functional Plant Biology 39(7) 609-618 https://doi.org/10.1071/FP12121
Submitted: 18 April 2012  Accepted: 18 May 2012   Published: 4 July 2012

Journal Compilation © CSIRO Publishing 2012 Open Access CC BY-NC-ND

Abstract

Nax1 and Nax2 are two genetic loci that control the removal of Na+ from the xylem and thereby help to exclude Na+ from leaves of plants in saline soil. They originate in the wheat ancestral relative Triticum monococcum L. and are not present in modern durum or bread wheat. The Nax1 and Nax2 loci carry TmHKT1;4-A2 and TmHKT1;5-A, respectively, which are the candidate genes for these functions. This paper describes the development of near-isogenic breeding lines suitable for assessing the impact of the Nax loci and their performance in controlled environment and fields of varying salinity. In young plants grown in 150 mM NaCl, Nax1 reduced the leaf Na+ concentration by 3-fold, Nax2 by 2-fold and both Nax1 and Nax2 together by 4-fold. In 250 mM NaCl, Nax1 promoted leaf longevity and greater photosynthesis and stomatal conductance. In the uppermost leaf, the Na+-excluding effect of the Nax loci was much stronger. In the field, Na+ in the flag leaf was reduced 100-fold by Nax1 and 4-fold by Nax2; however, Nax1 lines yielded 5–10% less than recurrent parent (cv. Tamaroi) in saline soil. In contrast, Nax2 lines had no yield penalty and at high salinity they yielded close to 25% more than Tamaroi, indicating this material is suitable for breeding commercial durum wheat with improved yield on saline soils.

Additional keywords: HKT, osmotic stress, salinity, salt tolerance, turgor.


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