Post on 26-Aug-2018
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):
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?
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)