8th INTERNATIONAL WHEAT CONFERENCE

SALINITy ToLeRANCe ANd NA + exCLuSIoN IN WheAT:
VARIABILITy, geNeTICS, mAPPINg PoPuLATIoNS ANd qTL
ANALySIS
Yuri Shavrukov, Manahil Baho, Nawar Shamaya, James
Edwards, Courtney Ramsey, Peter Langridge and Mark
Tester
Australian Centre for Plant Functional Genomics, University of Adelaide, Urrbrae, SA 5064,
Australia
E-mail Address of presenting author: yuri.shavrukov@acpfg.com.au
Salinity is a major abiotic stress and is likely to increase in severity with global warming.
Investigating the variability in Na + exclusion in wheat as a key component of salinity
tolerance is a first step in our research. Results of screening different species in the genus
Triticum (T. monococcum, T. urartu, Aegilops (T.) tauschii, T. dicoccoides, T. turgidum ssp.
durum and T. aestivum) suggested that there is much greater variation in Na + exclusion
and salinity tolerance within wild species of Triticum compared to cultivated wheat. The
best accessions have been selected for further study and for crossing.
In durum wheat (Triticum turgidum ssp. durum), two landraces originating from Afghanistan,
lines 740 and 752, were identified as the best sodium excluders from a screen
of 179 durum landraces. While most of the durum lines studied accumulated 200-240
mM Na + in their 3 rd leaf after 10 days growth in 150 mM NaCl, lines 740 and 752 accumulated
160 and 120 mM Na + , respectively. Tetraploid status of both accessions was
confirmed using both molecular markers to show the absence of the wheat D genome,
and cytologically (confirming 2n =28). We have now crossed both lines with elite Australian
durum cultivars and breeding lines, to introgress their salinity tolerance traits into
cultivated durum wheat. F 2 and F 1 B 1 progenies of four cross combinations between the
low Na + excluding lines and the Australian durum cultivars Kalka and Jandaroi as well
as two breeding lines, 53380 and Zbl, have been analysed. Clear segregation has been
found in all of the four F 2 progenies, with the Na + exclusion traits from lines 740 and
752 showing a dominance effect. Detailed analysis of segregation types in F 2 progenies
is currently underway. The analysis of backcross populations F 1 B 1 with Australian elite
durum wheat as recurrent parents, is also showing promising results. Based on the type
of segregations observed, we hypothesize that there exists either one novel gene for Na +
exclusion with two different alleles, or two distinct genes for Na + exclusion in the durum
landrace lines 740 and 752. The absence of known T. monococcum Na + exclusion genes,
Nax1 and Nax2, in all lines has been confirmed, with the exception of the breeding line
Zbl which had been generated from a line that was crossed with T. monococcum. Crossing
Zbl with line 752 produces offspring with superior Na + exclusion compared to either
parent. Conversely, there are also offspring with significantly higher Na + shoot accumulation.
We hypothesize that the superior plants contain both Nax1 and novel Na + exclusion
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