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

Salinity Biotic stress Drought Loss of biodiversity

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)

Perth Sydney Adelaide Brisbane Melbourne Hobart Cairns

Where rainfall exceeds crop use, and unused water escapes below the roots, rising water tables can bring the salt to the surface

WA NSW WA Secondary salinity – seepage or “rising watertable” salinity

Two types of dryland salinity

Salt rises to the surface Salt stays below ground

• P. Rengasamy

Aust J Exp Ag 2002;

“seepage salinity” surface sodicity is indicative of subsoil or “transient salinity”

Primary salinity – subsoil or “transient” salinity

Where crop use exceeds rainfall, salts concentrate in the root zone

Low rainfall areas (<250-300 mm) have natural subsoil salinity or “transient salinity”, not connected to water tables

Natural subsoil salinity (salt is low at the soil surface, and increases with depth)

soil surface 2 4 6 8 10

Metres below soil surface

50 100 150 mM NaCl (1/3 seawater)

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

NaCl (mM)

200 400 600 800

Shoot DW (% control)

20 40 60 80 100 120 tall wheatgrass wheat saltbush rice

seawater

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

Photo M. Lloyd

“ …and again in floods of Jan 2006”

Ed Barrett-Lennard, DAFWA & UWA

• 1. Tight control of salt entering plant with water –
• ver 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

What makes saltbush so tolerant?

Salt bladders

• n surface of

saltbush leaves

(scanning electron micrograph

by Richard Storey)

NaCl (mM) 50 100 150 200 250 300

Shoot growth (% control)

20 40 60 80 100

tall wheatgrass barley wheat durum wheat sea barleygrass

Diversity in salt tolerance in the wheat/barley family at the salinities found in the Australian wheat belt

Colmer, Munns and Flowers, Aust J Exp Agric (2005)

Durum wheat is used for pasta and couscous

10 20 30 40

Time after NaCl added (d)

1 2 3 4 5

Total dry weight (g)

Control Salt

Osmotic effect Salt- specific effect

Osmotic versus salt-specific effect of soil salinity on growth

bread wheat durum wheat

Munns et al. Aust J Plant Phys (1996)

Salt exclusion Tissue tolerance

Root cell - salt excluded Leaf cell - salt stored safely in vacuole NaCl NaCl

Two main mechanisms of salt tolerance

The two ways of avoiding salt toxicity

1. 2. 3.

• 1. Na+ uptake from soil
• 3. Removal of Na+ into sheath
• 2. Loading Na+ into the xylem

Control points for Na+ transport in plants

Selecting for natural variation in salt tolerance

Na+ concentration (mol gDW-1)

200 400 600 800 1000 1200 1400 Tamaroi Wollaroi Janz High Na+ Low Na+ durum landrace durum landrace (bread) (durum) (durum)

Accumulation of Na+ in leaves

Physiological mechanism of Nax1 and Nax2

Nax2 Nax1

Nax2: Unloads Na+ from the xylem in roots

(HKT1;5)

Nax1: Unloads Na+ from the xylem in roots and leaf base

(HKT1;4)

Physiological mechanism of Nax1 and Nax2

Backcrossing into Australian durum wheat cultivar

Unique durum derivative Line 149 (a result of a previous cross between Triticum monococcum and a durum rust-sensitive cultivar for the purpose

• f rust breeding)

durum cultivar Tamaroi

Richard James, CSIRO Plant Industry

Andrew Smart (PCT, Narrabri) - 2008

350 450 500 300 250 200 150 400

N 1 km

ECa (mS m-1)

350 450 500 300 250 200 150 400

N 1 km

350 450 500 300 250 200 150 400 350 450 500 300 250 200 150 400

N 1 km

ECa (mS m-1)

Munns et al, Nature Biotechnology, 2012

Salt-affected field in northern NSW

Using an EM meter to measure soil salt

Ray Hare, durum breeder, NSW DPI Richard James, CSIRO

0 - 20 20 - 40 40 - 60 60 - 80 80 - 90 BLOCK 3 BLOCK 2 BLOCK 1 50 100 150 200 250 300 Chloride concentration in soil solution (mM) Soil depth (cm)

Sodium and chloride increase with depth, to half-strength seawater

Taking leaf samples for Na analysis

Relationship between soil salinity and yield of durum wheat cultivar Tamaroi with Nax2 gene

ECa (DS/m)

260 280 300 320 340 360 380 400 420 440 460 480

Grain yield (t/ha)

0.5 1.0 1.5 2.0 2.5 3.0 3.5 Block 1 Block 2 Block 3

+ Nax2

• Nax2

Yield data from different sites with different salinity

Site mean yield (t/ha)

1.0 1.5 2.0 2.5 3.0 3.5

Yield (% Tamaroi)

70 80 90 100 110 120 130

200 309 336 400 236 (ECa)

Yuluma 2009 Ashley 2008 Ashley2009 (Block 1) (Block 2) (Block 3)

Nax2 lines 5004 5042

High salinity Moderate to low salinity

James et al. Funct. Plant Biol (2012)

Field 2, Moree 2009 Field 1 Block 1 Block 2 Block 3 Grain yield (% Tamaroi) 80 90 100 110 120 Moree 2008

*

Munns et al, Nature Biotechnology (2012)

Benefit of Nax2 on grain yield in selected trial sites

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