Presentation: Improving salt tolerance of wheat - The UWA Institute ...

IMPROVING SALTTOLERANCE OF WHEATRana MunnsCSIRO Plant Industry, andUniversity of Western Australia

The food demand gap

Environmental IssuesDroughtLoss of biodiversitySalinityBiotic stress

Outline of talk• Two types of dryland salinity in Australia• How native plants evolved to deal with it• How agriculture deals with it, through plantphysiology, genetics and plant breeding

Origin of salinity in Australia• Salt in the Australian landscape has mainly come fromthe sea via wind and rain• The concentration at the soil surface depends on therainfall and the type of vegetation• In higher rainfall areas (300-500 mm) rising water tablesbrings salt to the surface of cleared land• In low rainfall areas (250 mm and below), the salt staysbelow the soil surface, in the root zone

Areas in which there is land atrisk of rising water tables(National Audit 2001)CairnsBrisbanePerthAdelaideSydneyMelbourneHobart

WAWhere rainfall exceeds crop use,and unused water escapes belowthe roots, rising water tables canbring the salt to the surfaceWANSWSecondary salinity – seepage or “rising watertable” salinity

Two types ofdryland salinitySalt rises to the surface“seepage salinity”Salt stays below groundsurface sodicity is indicative ofsubsoil or “transient salinity”P. RengasamyAust J Exp Ag 2002;

Low rainfall areas (

Natural subsoil salinity(salt is low at the soil surface, and increases with depth)0 50 100 150 mM NaCl (1/3 seawater)Metres belowsoil surface2soil surface46810Based on YP Dang et al. Aust J Soil Res, (2010) Fig 5.

Rainfall in the south-west of WAIndian Ocean Climate Initiative Note No 5 (2005)

Indian Ocean Climate Initiative Note No 5 (2005)

Growth response of the world’s two staple crops,and the most useful two halophytes120Shoot DW (% control)10080604020ricewheatseawatertall wheatgrasssaltbush00 200 400 600 800NaCl (mM)

Old man saltbushAtriplex nummulariawith inter-rows of tallwheatgrassEd Barrett-Lennard,DAFWA & UWA

Farmers say:“Every saltbush plant paid foritself in the 2001/02 drought… “Photo. M. Lloyd“ …and again infloods of Jan 2006”Ed Barrett-Lennard, DAFWA & UWAPhoto M. Lloyd

What makes saltbush so tolerant?1. Tight control of salt entering plant with water –over 95% is excluded from leaves2. Cells in leaves can tolerate extremely highconcentrations – well over seawater concentrations3. Bladders on leaves excrete excess salt4. Seeds do not germinate until after heavy rain5. Some species are annuals, some perennials6. Fast growth

Salt bladderson surface ofsaltbush leaves(scanning electron micrographby Richard Storey)

Diversity in salt tolerance in the wheat/barley familyat the salinities found in the Australian wheat belt100Shoot growth (% control)80604020sea barleygrasstall wheatgrassbarleydurum wheatwheat00 50 100 150 200 250 300NaCl (mM)Colmer, Munns and Flowers, Aust J Exp Agric (2005)

Durum wheat is used for pasta and couscous

Total dry weight (g)Osmotic versus salt-specific effect ofsoil salinity on growth54ControlOsmotic effect3210bread wheatSaltdurum wheat0 10 20 30 40SaltspecificeffectTime after NaCl added (d)Munns et al. Aust J Plant Phys (1996)Munns, Schachtman, Condon, AJPP 1995

Two main mechanisms of salt toleranceThe two ways of avoiding salt toxicitySalt exclusionTissue toleranceNaClNaClLeaf cell -salt stored safelyin vacuoleRoot cell - salt excluded

Control points for Na + transport in plants3.3. Removal of Na + into sheath2.2. Loading Na + into the xylem1.1. Na + uptake from soil

Selecting for natural variation in salt tolerance

Accumulation of Na + in leaves1400Na + concentration (mol gDW -1 )120010008006004002000High Na + Tamaroi Wollaroi Low Na + Janzdurum (durum) (durum) durum (bread)landracelandrace

Physiological mechanism of Nax1 and Nax2Physiological mechanism of Nax1 and Nax2Nax1Nax1: Unloads Na +from the xylem inroots and leaf base(HKT1;4)Nax2Nax2: Unloads Na +from the xylem in roots(HKT1;5)

Backcrossing into Australian durumwheat cultivarUnique durumderivative Line 149(a result of a previouscross between Triticummonococcum and adurum rust-sensitivecultivar for the purposeof rust breeding)Richard James,CSIRO Plant Industrydurum cultivarTamaroi

Salt-affected field in northern NSWECa(mS m -1 )500450400350300250200150N1 kmAndrew Smart (PCT, Narrabri) - 2008Munns et al, Nature Biotechnology, 2012

Using an EM meter to measure soil saltRichard James, CSIRORay Hare, durum breeder,NSW DPI

Chloride concentration in soil solution (mM)Sodium and chloride increase withdepth, to half-strength seawater3002502001501005000 - 2020 - 40Soil depth (cm)40 - 6060 - 8080 - 90BLOCK 2BLOCK 3BLOCK 1

Taking leaf samples for Na analysis

Relationship between soil salinity and yield ofdurum wheat cultivar Tamaroi with Nax2 gene3.53.0Block 1Block 2Block 3Grain yield (t/ha)2.52.01.5+ Nax21.0- Nax20.5260 280 300 320 340 360 380 400 420 440 460 480ECa (DS/m)

Yield data from different sites withdifferent salinity130Ashley2009(Block 1) (Block 2) (Block 3)5004Yuluma2009Ashley20081205042Nax2 linesYield (% Tamaroi)1101009080High salinity(ECa) 400 336 309 236200701.0 1.5 2.0 2.5 3.0 3.5Site mean yield (t/ha)Moderate to lowsalinityJames et al. Funct. Plant Biol (2012)

120Benefit of Nax2 on grain yieldin selected trial sites*Grain yield (% Tamaroi)11010090800Field 1 Block 1 Block 2 Block 3Moree 2008Field 2, Moree 2009Munns et al, Nature Biotechnology (2012)

Crossing Nax genes from durum intobread wheatCarol Blake (CSIRO Plant Industry) makingcrosses between durum wheat (male) containingNax genes and bread wheat (female) parents

SUMMARYSalt underlies all Australian soilsWhere rainfall is low, crops use all the water so saltconcentrations increase in the subsoil. Crops mustbe salt tolerantWhere rainfall is high, water escapes below theroots and rising watertables bring salt to thesurface. Plants employed to lower watertables mustbe very salt tolerantGenetic improvement in salt tolerance will befastest when laboratory scientists work togetherwith agronomists and breeders

AcknowledgementsCSIRO Plant IndustryRichard JamesCarol BlakeCaitlin ByrtShaobai HuangEvans LagudahWolfgang SpielmeyerMark Tester, ACPFGMatthew Gilliham, Uni AdelaideCollaborating Breeders:Ray Hare, NSW DPITony Rathjen, Uni AdelaideAndrew and Jodie Crowe(growers, northern NSW)