Partitioning assimilates to optimize crop yieldPartitioning assimilates to optimize crop yield

John FoulkesJohn Foulkes

2nd UK-CIMMYT Wheat Workers Meeting, John Innes Centre, Norwich, 26–27 June 2007

Talk OutlineTalk Outline

Historical perspective: genetic gains in HI and spike indexMechanisms influencing partitioning amongst plant organs Future avenues for optimizing assimilate partitioningConclusions

Changes in grain yield and harvest index with breeding

Recent changes in yield and DM partitioning at harvestChanges in grain yield and harvest index with breeding

UK breeding: linear progress in yield potential and grains mUK breeding: linear progress in yield potential and grains m--22

Rialto (1995)

Austin et al. (1989)

NonNon--linear progress in biomass and HIlinear progress in biomass and HI

Grain yield Grain number

Biomass Harvest Index

M. Huntsman (1972)

Harvest index

Potential limits to HI: 0.62?Potential limits to HI: 0.62?Austin (1980) predicted theoretical maximum HI of 0.62 assuming:

– Constant above-ground DM– Leaf lamina (physiological) & chaff (structural) DM cannot

be decreased– Stem & leaf sheath DM can be reduced by 50%– Chaff DM can be increased pro rata to accommodate extra

grain

Crop components

Austin et al. 4 most modern vars

Austin 1980 Theor. max.

g/m2 % g/m2 %

Grain 707 0.49 895 0.62

Chaff 143 0.10 181 0.13

Leaf lam. 139 0.10 139 0.10

St & Shth 453 0.31 226 0.15

AGDM 1442 1441

Austin et al. 1980 ( 730/3637, 989/10, Armada, Benoist 10483)

Sherman et al. 2005 (Riband, Haven, Brigadier Rialto)

Comparison of recorded harvest indices in the UK with theoretical maximum value of 0.62

Crop components

Austin et al. 4 most modern vars

Austin 1980 Theor. max.

Shearman et al. 4 most modern vars

g/m2 % g/m2 % g/m2 %

Grain 707 0.49 895 0.62 888 0.51

Chaff 143 0.10 181 0.13 171 0.10

Leaf lam. 139 0.10 139 0.10 151 0.09

St & Shth 453 0.31 226 0.15 536 0.30

AGDM 1442 1441 1746

Comparison of recorded harvest indices in the UK with theoretical maximum value of 0.62

Austin et al. 1980 ( 730/3637, 989/10, Armada, Benoist 10483)

Sherman et al. 2005 (Riband, Haven, Brigadier Rialto)

Crop components

Austin et al. 4 most modern vars

Austin 1980 Theor. max.

Shearman et al. 4 most modern vars

Consort (1996) Rm 97 & 98

g/m2 % g/m2 % g/m2 % g/m2 %

Grain 707 0.49 895 0.62 888 0.51 1103 0.56

Chaff 143 0.10 181 0.13 171 0.10 195 0.10

Leaf lam. 139 0.10 139 0.10 151 0.09 183 0.09

St & Shth 453 0.31 226 0.15 536 0.30 490 0.25

AGDM 1442 1441 1746 1979

Comparison of recorded harvest indices in the UK with theoretical maximum value of 0.62

Austin et al. 1980 ( 730/3637, 989/10, Armada, Benoist 10483)

Sherman et al. 2005 (Riband, Haven, Brigadier Rialto)

• Increased DM partitioning to the spike with Rht is due to less competition from the growing stem in dwarf wheats.

• Some evidence final partitioning at anthesis appears to be the consequence of an allometricunfolding of early differences

Fischer & Stockman 1986Aust. J. Plant Physiol.

Spike index

Grains/spike

Heightcm

Talls (mean) 0.188 53.3 99

Dwarfs (mean) 0.231 56.2 63

Mechanisms underpinning changes in grain partitioning: competition between stem and spike pre-anthesis

Spike index (dwarfs) Spike index (talls)

Early events during stem elongation may important in affecting Early events during stem elongation may important in affecting ear partitioning at anthesis ear partitioning at anthesis

Siddique et al. 1989 FCR

‘Ear: stem ratio in old and modern Australian wheat varieties’

Predicted stem dry weight (mg) at ear dry weight = 1 mg

AP tall 73.0AP semidwarf 50.3KC tall 95.1KC semidwarf 76.0

• Semi-dwarfs had higher ratio ofear: stem growth rate than talls.

• Constant ratio between relative growth rates of ear and stem.

• Difference between tall and Rht isolinesevident soon after TS.

• Greater ear: stem ratio at anthesis forRht mainly due to a bigger intercept ofregression of In ear DM vs ln stem DM.

Ln stem dm vs ln ear dm during stem elongation

UK Breeding Progress 1972 – 1995: anthesis partitioning

M. Huntsman (1972)

Avalon (1980)

Rialto(1995)

Norman (1981)

Riband(1989)

Haven(1990)

Ear index Rialto (1996) = 0.149

Ear index M. Huntsman (1972) = 0.124

Growth and partitioning: UK reference crop cv Consort (released 1996)

Data: mean of 6 site seasons: ADAS Rosemaund,Boxworth& Sutton Bonington 97-98

Grain Yield (85% DM): 10.9 t/ha HI = 0.521

Ear index (at anthesis): 0.155

Anthesis partitioning: Consort UK (released 1996) and Bacanora CIMMYT (released 1988)

4

21

39

20

16GS61 GS61+3d

21

Ear

SolSt

Strst

LamIn shts

39

20

16

4 127

45

7

20

Consort mean 6 UK site-seasons 97-98; Bacanora mean 3 CIMMYT C. Obregon 04-06

Consort yield : 9.26 t/ha (HI 0.52)

Bacanora yield: 6.88 t/ha (HI0.41)

Future avenues for increasing ear Future avenues for increasing ear indexindexReduce partitioning to competing sinks: – Roots– Infertile tillers– Stems

• stem soluble CHO reserves• shorter peduncle

– Awns

Restricted scope to reduce leaf partitioning?

Optimising root partitioningOptimising root partitioning

Effects of genotype?– Rht ~ no effect of semi-dwarfs on root dry weight ratio

consistently observed across environments – IBL.1RS ~ ↑ root DW ratio– Phenology ~ earliness ↓ root DW ratio

Root distribution with depth may be more important than root dryweight ratio (synthetic derivatives)

0

0.1

0.2

0.3

0.4

Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep

Roo

t wt./

tota

l pla

nt w

t.

Gregory et al. 1976 J. Agric. Sci

Quantifying assimilate losses in nonQuantifying assimilate losses in non--surviving surviving (NS) shoots(NS) shoots

GS39ALL NS

GS61ALL NS

Brigadier 1191

Rialto 994 83 1525 33

Spark 1114 200 1521 21

Soissons 814 43 1486 5

Mean 1028 158 1503 25

SED (df 6) 107.7 36.5 85.5 11.7

421482307

• Some genetic variation in potential amount of dry matter wasted by non-surviving shoots.

• Cultivars for which shoot death was both greatin number and late flowering resulted in a netloss of >100 g m-2.

• Non-surviving shoots for cultivars withmore economic patterns of tillering ~ net loss ofdry matter less at 10–50 g m-2.

Sutton Bonington 1996 &1998Berry et al. 2003 FCR

DM (g m-2) in All or Non-surviving Shoots

L14 (Tin)

Rialto (-Tin)

L14 (+Tin)

Effects of tiller inhibition genes?Effects of tiller inhibition genes?

x

Collaboration M. Reynolds CIMMYT

PhD Study Reshmi Gaju

Dry weight in non-surviving shoots versus spike index at GS61 + 7 days in 16 L14 x Rialto DH lines (Obregon2006, irrigated)

Optimization of soluble stem carbohydrate reserves

Imaging MALDI spectrometery used to analyse hexosedissachride cross and longitudinal sections from stems of cv. Spark GS61+ 22d. Robinson et al. 2006 New Phytol.

• Stem storage1: -peduncle 22%- penutimate internode 29%- lower internondes 49%

Reported genetic ranges in % stem WSCt ha -1

0

2

4

6

8

10

Apr May Jun Jul Aug Sep

total

water soluble

Cv Mercia Boxwoth 1995

Range% WSC

Country No.. Genotypes

Source

24-43 UK

Australia

20-28 USA 12 Ehdaie& Waines 20061

Mexico

17 Foulkes et al. 1998

11-21 20 Ruuska et al. 20062

5-26 12 Reynolds et al. 2007

• Enzymes involved2:- sucrose 1-fructosyltransferase- sucrose : fructan 6-fructosyltransferase - fructan : fructan 1-fructosyltransferase - 1-fructan exohydrolase- 6-ketose exohydrolase

Stem water sol. CHO at GS61+75oCd (base temp. 0oCd) vs grain yield

Beaver x Soissons DHsRialto x Spark DHs

Beaver x Soissons 2001/2Rialto x Spark 2000/1

R2 = 0.13, P< 0.10, y = 0.32x + 8.1

R2 = 0.22***, y = 0.47x + 6.1

Relationship between stem soluble CHO reserves and yield in 2 UKDH populations

ADAS Gleadthorpe UK

Stem water sol. CHO at GS61+75oCd (base temp. 0oCd) vs grain yield

R2 = 0.13, P< 0.10, y = 0.32x + 8.1

Relationship between stem soluble CHO reserves and yield in CIMMYT L14 x Rialto DH population

L14 x Rialto DHs

Obregon 2006 (fully irrigated)

Beed et al. 2007 J. Ag. Sci, Camb.

Changes in dry weight for shoot components with shading during GS39-GS55

Controlg m-2

Shadingg m--22

Response to shade g m-2

SED

Leaf lamina 11 -31 -42

-81

-104

-35

-262

34

Structural stem 182 101 37

Soluble stem 68 -36 22

Ear 83 48 17

Total 344 82 67

Responses to shadeResponses to shade

ADAS Terrington

Mean 94-96

Genetic variation in peduncle length relative to plant height: Genetic variation in peduncle length relative to plant height: Avalon x Cadenza DH population

20

30

40

50

60 80 100 120

Plant height cm (to tip of ear)Pe

dunc

le le

ngth

cm

20

30

40

50

60 80 100 120

Plant height cm (to tip of ear)

Pedu

ncle

leng

th c

m

Rosemaund 2004 High Mowthorpe 2004

Avalon x Cadenza DH population

Data: permission of P. Berry (ADAS)

Reduction in structural stem DM Reduction in structural stem DM sink: shorter peduncle? sink: shorter peduncle?

Effects of awnsEffects of awnsAwns can double the net assimilation rate of the ear (Evans & Rawson 1970)Advantage of awns under drought related to xeromorphicstructure and high ratio between carbon exchange rate and transpiration rate (Blum 1986)Few and inconsistent effects of awns on bread wheat fertility reported when awnless and awned isolines compared (McKenzie, 1972; Weyhrich et al., 1994)

Above-ground dry matter, grain yield (85% DM), stem water soluble carbohydrate (WSC) at GS61+75oCd (base temp 0oC) in irrigated and unirrigated treatments in groups of awned and unawned doubled-haploid lines in the Beaver x Soissons population in 2001 and 2002. 2001 2002 Significance Irrigated Unirrigated Irrigated Unirrigated Year Irr ±Awns Year x

±Awns Irr x ±Awns

Awns2 Unawned Awns Unawned Awns3 Unawned Awns Unawned AGDM 100% DM t ha-1 15.65 15.74 12.65 12.42 13.47 12.46 11.23 10.03 * ** *** NS NS Grain yield t ha-1 85% DM 8.86 9.16 6.12 6.24 7.73 7.36 5.97 5.80 * *** *** 1 NS Stem WSC t ha-1 - - - - 3.39 3.06 2.67 2.45 - * *** - NS 1 = p≤ 0.10. 2 2001: Awned 20 lines and unawned 13 lines. 3 2002: Awned 24 lines and unawned 21 lines.

Foulkes et al. 2007 FCR

GAI Flag leaf areacm2

RUEPARg MJ-

Stem WSC t ha-

1

M. Huntsman 1972 5.72 40.9 2.482.412.662.84

0.22

1.71Hobbit 1978 4.89 39.0 2.06Mercia 1983 5.14 32.1 1.91Weston 1996 5.16 27.4 2.63

SED 0.52 0.55 3.0 0.26

Pre-anthesis RUEPAR and canopy traits at flowering. Mean of 4 site-seasons (Rosemaund & Terrington, 2000 & 2001)1

Changes in flag leaf traits … correlated with pre-anthesis RUE

1Foulkes et al. Phytopathology 2006

Shearman et al. 2005

Contribution of alien genes to optimized assimilate partitioning

• Agropyron 7DL.7Ag translocation ~ ↑ spike index (link with ABA?)

• Novel large spikes (Agropyron/Polonicum/ Morocco) ~ ↑ spike index (physiological basis?)

• Synthetic derivatives ~ effects on spike index?

• Rice Gn1 cytokinin oxidase (lateral meristem activity) ~ orthologuein wheat?

Novel parent L14: + 0.04 spike index cf. check Bacanora

Rational applications of Genomics to traits

Traits underlying spike index

Biochemical: Stem: fructan metabolism

Genomics platforms

Spike: cytokinin metabolism

Cellular: ABA conc in spike/floret

Plant/crop: Roots: ↑ root density at depthPhenology: advance GS31Tillers: ↑ tiller survivalStruct. stem: ↓ peduncle lnthLam: ↓ Flag leaf size/↑sp. wt

Transformation (overexpress genes); markers (QTLs, small map pops)Directed mutagenesis; transformation

Transcriptomics (Affymetrix array);Molecular mutational approaches; Candidate gene approaches (models)

Markers (QTLs, synteny); combinedmarker/transcriptomics; candidategene approaches (models)

AcknowledgementsAcknowledgements

Funders:

Collaborators:

Nottingham group: Reshmi Gaju (Post doc)

Liz Lloyd, John Alcock (technical staff)

Roger Sylvester-Bradley

Matthew Reynolds

John Snape