IMPROVING PHOTOSYNTHESIS IN WHEAT

Dr. Gemma Molero Wheat Physiology

CIMMYT

Genetic improvement is achieved through selection

Directly, for a primary trait (such as grain yield) in a

target environment

and with the complementary use of physiological traits and

their markers

Conventional breeding

Physiological/molecular breeding

Understanding of relatively simple crop-physiological attributes that determine yield in a wide range of conditions may be instrumental for assisting future breeding

Physiological interventions in breeding:

Design conceptual models of improved adaptation

Develop precision phenotyping platforms

Explore genetic resources for new sources of traits

Facilitate gene discovery for molecular breeding:

• development of experimental populations

• high throughput phenotyping

Combine complementary traits through strategic

crossing and early generation selection

Bottlenecks to improve yield are identified through experimentation under targeted environments

SAWYT Y10-11, J. Pietragalla

DROUGHT

YIELD = WU x WUE x HI

HEAT

YIELD = LI x RUE x HI

YIELD POTENTIAL

YIELD = LI x RUE x HI

How to raise the yield potential?

Better performance under high temperature

Better performance under water limitation

Yield Potential (YP): is the yield obtained of an adapted cultivar when grown with the best

agronomical management and without any biotic or abiotic stress (Evans, 1993)

YP= LI x RUE x HI

LI: Light Intercepted

HI: Harvest Index (grain weight/total Biomass)

RUE: Radiation Use Efficiency (utilization of solar radiation per unit of dry matter production)

Conceptual model for yield potential

YIELD = LI x RUE x HI

Pre-grainfill (HI): •Spike Fertility

grain no./weight potential phenological pattern (Ppd/Vrn) Avoid floret abortion (?)

•Lodging resistance •Abort weak tillers

Grain-filling (HI/RUE): •Partitioning to grain (HI) •Adequate roots for resource capture (HI/RUE)

Pre-grainfill (RUE/LI): • Light interception (LI) • CO2 fixation (RUE)

Rubisco C4 type traits

Grain-filling (RUE/LI): • Canopy photosynthesis (RUE/LI)

light distribution N partitioning spike photosynthesis stay green

Adapted from Reynolds et al., 2012

WHEAT YIELD CONSORTIUM (WYC): An international collaboration to raise the

Yield Potential of Wheat

• WYC is an international partnership seeks to increase wheat yield potential by 50 percent within 20 years to address predicted demand for wheat in that timeframe

• Beginning of activities 2011 • 34 research organizations (from 21 different

countries) +NARS are sharing expertise, facilities, and seed to boost the crop’s yield potential using advanced science

34 PARTNERS FROM 21 DIFFERENT COUNTRIES + NATIONAL AGRICULTURAL RESEARCH SYSTEMS

WHEAT YIELD CONSORTIUM (WYC): An international collaboration to raise the

Yield Potential of Wheat

WHEAT YIELD CONSORTIUM (WYC): An international collaboration to raise the

Yield Potential of Wheat

Wheat Yield Consortium (WYC):

A Consortium to raise the Yield Potential of Wheat

Markers

Theme 1 :

Increasing

photosynthetic

c apacity and

e ffici ency

Theme 2 :

Optimising

partitioning and

lodging

resistance

Theme 3 : Accumulating and deploying

yield potential traits

Germplasm

Complementary approaches to raise the yield potential of wheat

Bottleneck to yield: RUE

• Photosynthetic capacity barely changed since wheat breeding began

• Basic research suggests substantial improvements in yield are theoretically possible (Long et al., 2006)

• C4 crops (e.g. maize, sorghum, millet) show up to 50% greater RUE than C3 species (wheat, rice, beans, potatoes, most vegetables)

SOLAR ENERGY

BIOMASS

ENERGY LOSS ENERGY LOSS

BIOMASS

CIMCOG 2 YEARS

Biomass (g m-2)

1200 1400 1600 1800 2000

Yie

ld (

g m

-2)

400

500

600

700

800

900

1000

r = 0.826***

Bread Wheat Durum Wheat

Increase 20% Biomass

Increase 20% Yield Biomass must be increased

to raise yield potential

How to increase Biomass?

Increasing photosynthetic capacity and efficiency

Relationship between yield and biomass

Theme 1: Increase photosynthetic capacity and efficiency in wheat (transgenic and non-transgenic)

Optimising and modelling canopy establishment, photosynthesis and duration

Phenotypic selection for photosynthetic capacity and efficiency Phenotypic selection for ear photosynthesis

Chloroplast CO2 pumps Increasing RuBP Regeneration Replacement of LS Rubisco

Improving the thermal stability of Rubisco activase

MODIFICATION OF METABOLISM

Summary of Photosynthesis

RuBP

PRKaseSBPase

FBPase

RubiscoCO2(ci)

CO2(ca)

Triose-P

ATPsyn

PSI

PSII

ATP

electrontransport

H+

PPFD

NADPH

Calvin Cycle PhotophosphorylationStomatastroma thylakoid membrane

guard cell (A)

epidermis mesophyll chloroplasts

A schematic representation of the main processes in C3

photosynthesis in higher plants

How to Improve Photosynthetic Capacity and Efficiency in Wheat?

(Parry et al., 2011. JXB 62(2): 453-67)

• Improving Rubisco efficiency and regulation Thermoestability / RUBP regeneration

• Duration of Photosynthesis Early ground cover / Stay Green / Grain Filling duration

• Interception of Radiation Amount / Composition / Area / Angle

• Extent of down regulation Photoprotection / Rubisco activase

• Rate of photosynthesis Net Photosynthesis m-2 / Chloroplasts CO2 pumps / Photorespiration

• Ear photosynthesis

Dohleman et al. 2009 Plant Physiol., 150:2104-2115

Long et al 2006. Plant, Cell & Environment 29, 315-330

•CO2

•Light

•Temperature

•Water availability

Ways to increase net photosynthesis

in current C3 crops

Modification Predicted Increase (%)

Time scale (years)

Increased RuBP regeneration 10 5

Increased conductance 5 5

Faster Rubisco with increased specificity

60 15

Faster Rubisco without oxygenase activity

100 25

Optimised Rubisco regulation 10 10

C4 single cell 10 10

C4 Kranz anatomy 50 20

Long et al 2006. Plant, Cell & Environment 29, 315-330.

Is C4 ‘wide-crossed’ wheat feasible?

• C4 chromatin has been introduced wheat but is unstable (Laurie, Bennett, 1989)

• A complete set of maize chromosomes has been introduced into oat (Kynast et al., 2001)

• C4 enzymes expressed in oat–maize chromosome addition lines (Knowles et al., 2008)

• Wheat is crossed routinely with maize to make DH; screening DHs for maize chromatin could provide a low cost proof of concept

Photosynthesis vs. Yield (Richards, 2000 JXB)

Olivares et al., 2007 (Richards, 2002 Crop Sci.)

i.e. Can breeders select for higher stomatal conductance and thus obtain higher yields?

• Genotypic differences have been reported for stomatal conductance in wheat (e.g. Condon et al. 1990; Fischer et al. 1998; Rebetzke et al. 2001), suggesting that this trait may be targeted for improving the adaptation of the crop

• Strong and Positive associations between leaf conductance and grain yield conducted under irrigated conditions in Mexico (Fischer et al. 1998) and the United States (Lu et al. 1998) have been reported

i.e. Can breeders select for higher stomatal conductance and thus obtain higher yields?

• Studies with Pima cotton have shown that selection of high-conductance F2 progeny from a cross between high- and low-conductance parents produces high-conductance F4 lines with higher lint yields than low-conductance lines have (Radin et al. 1994; Ulloa et al. 2000)

• These experiments indicate that high stomatal conductance could be used as a selection trait for high yields in irrigated crops (Barbour et al. 2000).

Develop precision phenotyping for increased photosynthetic capacity and efficiency

TIME

PRECISSION

NUM. OF GENOTYPES

RESOLUTION m mm

s min

1000’s 10’s

+ -

SPAD

IRGA

COST $ $$$

Target Environment

Stressed environment

Drought

Large and small populations

Light and dark fluorescence

Heat

Large

population

Light and dark fluorescence

Small population

Resources available*

Low

Light and dark fluorescence

High

Gas exchange and light and dark fluorescence

Yield potential

Large population

Light and dark fluorescence

Small population

Resources available*

Low

Light and dark fluorescence

High

Gas exchange and light and dark fluorescence

Where? When?

How? When?

Establish Standard Phenotyping Protocols

SPAD: chlorophyll area meter SPECTRORADIOMETER: pigment composition, water content…

CEPTOMETER: light intercepted by the canopy, LAI

CANOPY TEMPERATURE: transpiration, stomatal conductance

POROMETER: stomatal conductance

IRGA: photosynthetic rate, transpiration rate, stomatal conductance, Ci, …Fluoresncece

FLUOROMETER: flurescence of chlorophyll, ETR…

CO2 CO2

(Ci) (Ca)

NADPH

ATP

Photophosphorylation Thylakoid membrane

Calvin Cycle Stroma

Stomata

Leaf epidermis Mesophyll cell Chloroplast

CHO’s

PS II PS I ATP

Synthase

PQ

Cyt

complex

PC

FeS

NADP+

red Fed

H2O ½ O2

2 H+ H+

2 H+

ATP

ADP + Pi

NADP+ + H+

2 H+

e-

NADPH

Light dependent reactions

SPAD

SPECTRORADIOMETER FLUOROMETER

CEPTOMETER

RuBP

Rubisco

FBPase

SBPase

PRKase

Triose-P

NADPH

ATP

CO2 Dark Reactions

CO2 CO2

(Ca) (Ci)

Stomata

Leaf epidermis

CANOPY TEMPERATURE

POROMETER

IRGA

Photosynthetic Capacity and Efficiency (Theme 1)

G. Molero, S. Sukumaran, J. Evans, V. Silva-Pérez, T. Condon, R. Furbank, JL Araus, R. Sánchez-Bragado, MA Parry,

E.Carmo-Silva, L. Robledo-Arratia

First steps for the identification of genetic variation in gm and photorespiration of wheat plants

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

g m o

r g s

(m

ol C

O2 m

-2 s

-1 )

Stomatal conductance Mesophyll conductance

L. Robledo-Arratia et al.

For some genotypes of the Watkins collection, gm was almost 20% higher than in Paragon

MEX

PLA

T, 2

01

3-2

01

4

Genetic variation in Spike Photosynthesis, molecular markers and development of surogates

Genotypes Direct

Measurements

with LI-6400XT

G. Molero et al.

Genetic variation in Spike Photosynthesis, molecular markers and development of surogates

Molecular Markers for SP were identified in chromosome 3A, 3B, and 7A through linkage mapping

PVE = 10% PVE = 10% PVE = 24%

Photosynthetic contribution of the ear to grain filling inferred from carbon isotope signature

S. Sukumaran

G. Molero et al.

• BIOMASS

• Greenseeker - Normalized difference vegetation index (NDVI)

• WATER SOLUBLE CARBOHIDRATES

SURROGATES

YP traits considered in strategic crosses: YIELD = LI x RUE x HI

SINKS -pre-grainfill- (HI):

•Spike Fertility •grain number •kernel weight •spike index •avoid floret abortion

SINK (grain-filling)

•Harvest index

SOURCE (pre-grainfill):

• Light interception (LI)

• Canopy temp

• Growth rate

SOURCE (grain-filling):

• Canopy photosynthesis (RUE/LI) •Canopy temp •Stem WSC •stay green

Early generation selection methodologies

Visual selection ++

(Markers in parent selection) Spectral reflectance

Canopy temperature

Performance traits of 1st WYCYT under optimal crop management, NW Mexico, 2012

YIELD BIOM TKW HI Grains/ Spikes/ Grains/ Maturity Height Infertile

g/m2 g/m2 g m2 m2 spike d cm spklts

Avg NEW (n=5) 815 2220 46.1 0.37 17795 381 47.0 135 109 1.4

Avg CONV (n=5) 800 2050 48.4 0.39 16560 350 48.1 134 112 1.7

% difference 1.9 8.3 -4.7 -5.5 7.5 9.1 -2.3 1.3 -2.5 -16.9

NEW lines of 1st WYCYT

BCN/RIALTO//ROLF07 822 2130 39.8 0.39 20620 403 50.9 138 107 1.1 CMH79A.955/4/AGA/3/4*SN64/CNO67

//INIA66/5/NAC/6/RIALTO/7/ROLF07 815 2110 50.0 0.39 16485 359 46.0 133 109 2.2

NL623/W-78//ROLF07 822 2135 47.1 0.39 17375 373 46.8 135 110 1.1 WBLL1//YANGLING

SHAANXI/ESDA/3/ROLF07 810 2420 46.3 0.34 17425 404 44.0 136 112 1.2 WBLL1//YANGLING

SHAANXI/ESDA/3/ROLF07 809 2300 47.5 0.36 17065 367 47.5 135 108 1.7

Elite Conventional Checks TACUPETO

F2001/BRAMBLING*2//KACHU 836 2015 51.0 0.42 16330 300 55.1 136 109 1.6

QUAIU 786 2045 48.9 0.39 16310 370 44.4 133 115 1.4

SOKOLL 777 2110 47.2 0.37 16255 358 45.4 132 108 1.8

WBLL1*2/KUKUNA 806 1990 47.3 0.41 17115 319 54.0 132 117 1.7 BABAX/LR42//BABAX*2/3/KURUKU 796 2080 47.6 0.38 16795 401 41.8 135 111 2.2

LSD 83 364 5.6 0.05 2758 74 10.2 2.9 6.9 1.0

Yield (t/ha) for sites at: Bangladesh Jessore

China Inner Mongolia

India Indore

India Karnataka

India Ludhiana

Pakistan Islamabad

(Mega-environment -ME-) ME5 ME6 ME4 ME1 ME1 ME1

Local Checks (2) 5.44 2.04 4.12 4.15 6.14 3.64

CIMMYT CHECKS (3) 4.80 0.81 3.80 4.11 5.14 3.05

BEST 3 NEW 5.09 1.85 3.95 4.11 5.55 2.87

BEST 5 NEW 4.95 1.78 3.88 3.99 5.29 2.68

% of best 3 NEW/Local check -7 -9 -4 -1 -9 -21

% of best 3 NEW/CIMMYT checks 6 130 4 0 8 -6

% of best 5 NEW/CIMMYT checks 3 121 2 -3 3 -12

LSD for full trial 0.57 na 0.77 0.88 0.81 0.67

Yield of best performing NEW lines (at each site) v local and same 3 CIMMYT checks, 1st WYCYT 2013:

Sites where local check out-yielded NEW lines

Yield of best performing NEW lines (at each site) v local and same 3 CIMMYT checks, 1st WYCYT 2013:

Sites where NEW lines out-performed local check

Yield (t/ha) for sites at: Bangladesh Rajshahi

Egypt Sohag

India New Dheli

India Dharwad

India Ugar

India Varanasi

Iran Karaj(1)

Iran Karaj(2)

Nepal Bhairahawa

Pakistan Faisalabad

Pakistan Nowshera

Mexico El Batan

(Mega-environment -ME-) ME5 ME1 ME1 ME4 ME4 ME5 ME7 ME7 ME5 ME4 ME1 ME2

Local Checks (2) 3.51 10.09 5.02 2.87 3.40 3.84 6.57 4.14 2.76 2.52 3.46 5.68

CIMMYT CHECKS (3*) 3.25 11.87 4.90 2.55 4.57 3.83 6.04 4.84 2.14 2.25 3.39 6.33

BEST 3 NEW 3.93 13.06 5.44 2.98 4.98 4.71 6.94 5.13 2.87 2.74 3.71 6.96

BEST 5 NEW 3.80 12.94 5.39 2.96 4.82 4.60 6.82 4.99 2.76 2.63 3.59 6.80

% of best 3 NEW/Local check 12 30 9 4 45 23 6 24 4 9 7 23

% of best 3 NEW/CIMMYT checks 21 10 11 17 9 23 15 6 34 22 10 10

% of best 5 NEW/CIMMYT checks 17 9 10 16 6 20 13 3 29 17 6 8

LSD for full trial 0.76 0.26 0.83 0.71 1.30 0.53 1.61 2.20 1.04 0.67 1.20 1.00

*CIMMYT CHECKS: QUAIU, TACUPETO F2001/BRAMBLING*2//KACHU, WBLL1*2/KAKUNA

Biomass of best performing NEW lines (at each site) v local and same 3 CIMMYT checks, 1st WYCYT 2013:

All sites (where biomass measured)

Bangladesh Rajshahi

Bangladesh Jessore

India Dharwad

India Indore

India Karnataka

India Ludhiana

India Ugar

Nepal Bhairahawa Average

(Mega-environment -ME-) ME5 ME5 ME4 ME4 ME1 ME1 ME4 ME5

Biomass (t/ha)

Local Checks (2) 12.0 13.4 10.1 10.5 14.0 14.2 18.5 5.6 12.3

CIMMYT CHECKS (3) 13.6 14.3 9.8 11.2 14.9 13.8 20.7 5.5 13.0

BEST 3 NEW 16.6 18.1 10.6 12.4 15.8 15.1 21.8 6.6 14.6

BEST 5 NEW 16.5 17.8 10.3 12.1 15.2 14.6 21.5 6.5 14.3

% of best 3 NEW/Local check 38 35 5 19 12 7 18 19 19.1

% of best 3 NEW/CIMMYT checks 22 26 8 11 6 10 6 20 13.5

% of best 5 NEW/CIMMYT checks 21 24 5 8 3 6 4 17 10.9

LSD for full trial 3.1 2.8 2.8 2.7 2.1 3.0 2.9 1.5

RUE improved but partitioning and wide adaptation need fine tuning

• Considering individual sites, 3 best NEW lines showed on average 8% more yield and 20% more biomass (RUE) than local checks

• Considering average response of lines across all environments, NEW lines showed clear advantage in biomass but not necessarily yield. – Not unexpected when initiating novel crossing strategies, where local & broad

adaptation not selection criteria

• Excellent expression of RUE illustrates potential for yield improvement, IF adaptation to achieve favorable expression of partitioning is improved in tandem with RUE

• Differences at MEXPLAT often reflected in even larger benefits at international sites.

• Proof of concept that YP can be increased through strategic crosses of source & sink related traits using elite breeding material

Next steps

• Best performing NEW lines studied side by side with parents to identify and understand interaction among traits.

• Best crosses made into mapping populations to: – understand gene action

– identify candidates for gene discovery, cloning, and MAS

• Trait knowledge base expanded using: – Exotic sources such as primary synthetics

– Latest outputs from WYC and in the coming years from IWYP research

Conceptual models of YP traits: YIELD = LI x RUE x HI

SINKS -pre-grainfill- (HI):

•Spike Fertility •grain no. & weight potential •phenological pattern (Ppd/Vrn/Eps) •Avoid floret abortion

•Abort weak tillers •Lodging resistance (roots, stems)

SINK (grain-filling)

•Partitioning to grain (HI)

•Adequate roots for resource capture (HI/RUE)

SOURCE (pre-grainfill):

• Light interception (LI) • CO2 fixation (RUE)

•Rubisco/regulation •C4 type traits

SOURCE (grain-filling):

• Canopy photosynthesis (RUE/LI) • light distribution •N partitioning •spike photosynthesis •stay green

Expected outputs of WYC

• 10-50% increased biomass (10-25 years)

• Harvest index >/= 0.5

• Structural failure improbable in 90% of years

• Simultaneous expression of all characteristics

in most major wheat agro-ecosystems.

• Spill-over effects into marginal environments

(Lantican et al., 2003)