IMPROVING SALT TOLERANCE OF WHEAT Rana Munns CSIRO Plant Industry, - PowerPoint PPT Presentation

IMPROVING SALT TOLERANCE OF WHEAT Rana Munns CSIRO Plant Industry, and University of Western Australia

The food demand gap

Environmental Issues Loss of biodiversity Drought Biotic stress Salinity

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

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

Areas in which there is land at risk of rising water tables (National Audit 2001) Cairns Brisbane Perth Sydney Adelaide Melbourne Hobart

Where rainfall exceeds crop use, WA and unused water escapes below the roots, rising water tables can bring the salt to the surface NSW WA Secondary salinity – seepage or “rising watertable” salinity

Two types of dryland salinity Salt rises to the surface Salt stays below ground “seepage salinity” P. Rengasamy surface sodicity is indicative of Aust J Exp Ag 2002; subsoil or “transient salinity ”

Low rainfall areas (<250-300 mm) have natural subsoil salinity or “transient salinity”, not connected to water tables Where crop use exceeds rainfall, salts concentrate in the root zone Primary salinity – subsoil or “transient” salinity

Natural subsoil salinity (salt is low at the soil surface, and increases with depth) 0 50 100 150 mM NaCl (1/3 seawater) Metres below soil surface soil surface 2 4 6 8 10 Based on YP Dang et al. Aust J Soil Res, (2010) Fig 5.

Rainfall in the south-west of WA Indian 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 halophytes 120 100 seawater Shoot DW (% control) 80 60 40 saltbush rice 20 tall wheatgrass wheat 0 0 200 400 600 800 NaCl (mM)

Old man saltbush Atriplex nummularia with inter-rows of tall wheatgrass Ed Barrett-Lennard,DAFWA & UWA

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

What makes saltbush so tolerant? 1. Tight control of salt entering plant with water – over 95% is excluded from leaves 2. Cells in leaves can tolerate extremely high concentrations – well over seawater concentrations 3. Bladders on leaves excrete excess salt 4. Seeds do not germinate until after heavy rain 5. Some species are annuals, some perennials 6. Fast growth

Salt bladders on surface of saltbush leaves ( scanning electron micrograph by Richard Storey)

Diversity in salt tolerance in the wheat/barley family at the salinities found in the Australian wheat belt 100 80 Shoot growth (% control) sea barleygrass 60 tall wheatgrass 40 barley 20 wheat durum wheat 0 0 50 100 150 200 250 300 NaCl (mM) Colmer, Munns and Flowers, Aust J Exp Agric (2005)

Durum wheat is used for pasta and couscous

Osmotic versus salt-specific effect of soil salinity on growth 5 4 Total dry weight (g) Control Osmotic effect 3 2 bread wheat 1 Salt- Salt specific durum wheat effect 0 0 10 20 30 40 Time after NaCl added (d) Munns et al. Aust J Plant Phys (1996)

Two main mechanisms of salt tolerance The two ways of avoiding salt toxicity Salt exclusion Tissue tolerance Leaf cell - salt stored safely NaCl in vacuole NaCl Root cell - salt excluded

Control points for Na + transport in plants 3. Removal of Na + into sheath 3. 2. Loading Na + into the xylem 2. 1. Na + uptake from soil 1.

Selecting for natural variation in salt tolerance

Accumulation of Na + in leaves 1400 1200 Na + concentration (  mol gDW -1 ) 1000 800 600 400 200 0 High Na + Low Na + Tamaroi Janz Wollaroi (bread) durum (durum) (durum) durum landrace landrace

Physiological mechanism of Nax1 and Nax2 Physiological mechanism of Nax1 and Nax2 Nax1 Nax1 : Unloads Na + from the xylem in roots and leaf base Nax2 (HKT1;4) Nax2 : Unloads Na + from the xylem in roots (HKT1;5)

Backcrossing into Australian durum wheat cultivar Unique durum derivative Line 149 (a result of a previous Richard James, cross between Triticum CSIRO Plant Industry monococcum and a durum rust-sensitive cultivar for the purpose of rust breeding) durum cultivar Tamaroi

Salt-affected field in northern NSW ECa ECa (mS m -1 ) (mS m -1 ) 500 500 500 500 450 450 450 450 400 400 400 400 350 350 350 350 300 300 300 300 250 250 250 250 200 200 200 200 150 150 150 150 N N N 1 km 1 km 1 km Munns et al, Nature Biotechnology, 2012 Andrew Smart (PCT, Narrabri) - 2008

Using an EM meter to measure soil salt Ray Hare, durum breeder, Richard James, CSIRO NSW DPI

Sodium and chloride increase with depth, to half-strength seawater 300 Chloride concentration in soil solution (mM) 250 200 150 100 50 BLOCK 1 0 BLOCK 2 0 - 20 20 - 40 BLOCK 3 40 - 60 60 - 80 80 - 90 Soil depth (cm)

Taking leaf samples for Na analysis

Relationship between soil salinity and yield of durum wheat cultivar Tamaroi with Nax2 gene 3.5 Block 1 Block 2 3.0 Block 3 2.5 Grain yield (t/ha) 2.0 + Nax2 1.5 1.0 - Nax2 0.5 260 280 300 320 340 360 380 400 420 440 460 480 ECa (DS/m)

Yield data from different sites with different salinity Ashley2009 Ashley Yuluma 2008 (Block 1) (Block 2) 2009 (Block 3) 130 5004 Nax2 lines 5042 120 Yield (% Tamaroi) 110 100 90 80 Moderate to low High salinity salinity (ECa) 336 236 200 400 309 70 1.0 1.5 2.0 2.5 3.0 3.5 Site mean yield (t/ha) James et al. Funct. Plant Biol (2012)

Benefit of Nax2 on grain yield in selected trial sites * 120 Grain yield (% Tamaroi) 110 100 90 80 0 Field 1 Block 1 Block 2 Block 3 Field 2, Moree 2009 Moree 2008 Munns et al, Nature Biotechnology (2012)

Crossing Nax genes from durum into bread wheat Carol Blake (CSIRO Plant Industry) making crosses between durum wheat (male) containing Nax genes and bread wheat (female) parents

SUMMARY Salt underlies all Australian soils Where rainfall is low, crops use all the water so salt concentrations increase in the subsoil. Crops must be salt tolerant Where rainfall is high, water escapes below the roots and rising watertables bring salt to the surface. Plants employed to lower watertables must be very salt tolerant Genetic improvement in salt tolerance will be fastest when laboratory scientists work together with agronomists and breeders

Acknowledgements CSIRO Plant Industry Mark Tester, ACPFG Richard James Matthew Gilliham, Uni Adelaide Carol Blake Caitlin Byrt Collaborating Breeders: Shaobai Huang Ray Hare, NSW DPI Evans Lagudah Tony Rathjen, Uni Adelaide Wolfgang Spielmeyer Andrew and Jodie Crowe (growers, northern NSW)