Winter wheat: Selection for weed competitiveness in ... · Winter wheat: Selection for weed...

1

Winter wheat: Selection for weed competitivenessin organic and low-input cropping systems

Prof. Dr. Ulrich Köpke,

Institute of Organic Agriculture, University of Bon n, Germany

Reunion FSOV Adventice September 17, 2007, Paris, France

IOL

www.iol.uni-bonn.de

WECOF -Strategies of weed control in Organic FarmingSite specific strategies

Breeder manual


2

Basic growth conditions ( compared with mainstream agriculture):

Limited soil-nutrient availability esp.nitrogenNo split - application of nitrogenN :f ( precrop, rotation, retarded mineralisation ) Retarded early developmentLimited tilleringLimited LAILimited LADLimited crop ground coverLimited WUELimited light interceptionLimited yield

Mechanical weed controlSuboptimal spacing

Direct control of pathogens limited

IOL


Main topics mentioned:

Nutrient management / efficiencyCompetitiveness against weedsPathogensProduct quality

All related to morphological features

Crop ideotypes for organic cerealcropping systems

IOL


3

Target goals

Wax coating

Target area

Baking quality

Microbiological hygienicquality

Mycotoxins

Product quality

Yield performance

Utilisation

Uptake

Drought resistance

N-EfficiencyRoot-length-density

Root surface

Rooting depth

Nutrient uptake / -efficiency

Cereal ideotypes ( Wheat ) for organic Agriculture

Shading ability

Weed competitivenessPlant morphology

Soil covering

Tillering

CompetitivenessLeaf inclination

I OL

Morphological

features

Plant height

Distance: flagleaf -ear

Distance: flagleaf – F - 1

Pathogenes

Septoria disease

Fusarium disease

Target goals

Wax coating

Target area

Baking quality


Mycotoxins

Product quality

Baking quality


Mycotoxins

Product quality

Yield performance

Utilisation

Uptake

Drought resistance


Root surface

Rooting depth


Yield performance

Utilisation

Uptake

Drought resistance


Root surface

Rooting depth



Shading ability


Soil covering

Tillering


Shading ability


Soil covering

Tillering


I OLI OL

Morphological

features

Plant height



Pathogenes

Septoria disease

Fusarium disease

Plant height



Pathogenes

Septoria disease

Fusarium disease

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During phase of tillering (GS 25): Breeding targets

Competition against weeds mainly based on shoot growth rate and speed of development.

f (root growth)

number of crown roots: f (tiller number*plant-1)

• Early prostrate growth beneficial under conditions of summerdrought ( WUE increased )

• Early shaders are often also later shaders

• Allelopathic exudates may be beneficial

Rapid early development, high crop coverage:

High tillering ability


4

Apera spica venti as affected by winterwheat cultivars

Rapid early development, plant height and allelopathic exudatesmay be beneficial

Controlling weeds - Cereals: normally not hoed ! Problem weeds need to be hoed

Spacing suboptimal

.

: Adapted morphology

Optimized distribution of limited leaf areaPlanophile leaf inclinationTaller crop /longer culms

Competitiveness against weeds limited

�

Breeding target

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5

Relationship among leaf angle, solar radiation at leaf surface and light response curve for a red clover leaf

Source: GARDNER, Franklin P.,Physiology of crop plants‘ IOL


Relationship among leaf orientation, leafphotosynthesis, LAI and total plot photosynthesis

Leaf angle From

Horizontal

Leaf Photosynthetic Rate

(mg CO2 * dm-2 * hr-1)

LAI to Intercept Most Light 1)

Total Plot Photosynthesis (mg CO2 * dm-2 Bodenfläche * hr-1)

0 33 1 33 60 31 2 62 75 26 4 104 85 12 10 120

1) Assuming perfect leaf placement – this would also correspond to critical LAI.

(GARDNER et al. 1985)

6

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Leaf inclination influencing rate of photosynthesis (GS 39-75)

Erectophile: beneficial for LAI > 3.5 Planophile: beneficial for LAI < 3.0

(DE WIT 1965)

Optimize leaf area distribution by using planophile typeswhen LAI limited esp. when spacing suboptimal.

Selection criteria: Use ‚crop ground cover‘in breeding program


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7

Light measurement in a winter wheat plot with a Line Quantum Sensor LI-191SA and a LI-190SA Sensor (Reference)

EISELE 1992

(Site: Wiesengut,1989)

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SPERBER (erectophile)CAROLUS (planophile)

607:50 8:40 9:20 10:20

Time

11:20 12:20 13:20 14:40 15:50

70

80

90

100

Cultivar

Shading [ % ]

Daily course of ground shading measured on soil surface under the cultivars Sperber and Car olus

8

EISELE 1992 (Wiesengut 1990, EC 33)

Unkrautregulation/ KonkurrenzkraftReunion FSOV Adventice September 17, 2007, Paris, France

Lepidium sativum in boxes under winterwheat cultivars Carolus (planophil, bottom) and Sperber (erectophil, top), grown from 3.May - 15.June 1990

Dry weight production of Lepidium sativum L. in relationto total shading at growth stages EC 30-70

(EISELE & KÖPKE 1997) erectophile planophile

% Total shading (3.5.-15.6.)

Dry weight (g 0.1m-2)

95 95.5 96 96.5 97 97.5 98 98.5 990

2

4

6

8

10

Y = 178.7-1.80X

R2 = 62.30 %**

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9

Dry weight production of Lepidium sativum L. in relationto total shading at growth stages EC 30-70

(EISELE & KÖPKE 1997) erectophile planophile

% Total shading (3.5.-15.6.)

Dry weight (g 0.1m-2)

95 95.5 96 96.5 97 97.5 98 98.5 990

2

4

6

8

10

Y = 178.7-1.80X

R2 = 62.30 %**

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(KÖPKE & EISELE 1997)

Weed ground covering under two winter wheat cultivars

0

5

10

15

20

25

30

35

40

Carolus planophile

Sperber erectophile

% Weed ground covering

12 cm 24 cm

a b b c

Row distance


Compensating sub-optimal spacing with planophile type

10

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Jae7.htm 24/09/01 CD

Weed ground cover (BBCH 33-37) as a function of wheatcoverage (BBCH 30= (1998)

R2 = 0,48**

0

5

10

15

20

25

30

35

20 30 40 50 60 70

Wheat ground cover

Wee

dgr

ound

cove

r

Apollo 12cm

Apollo 17cm

Carolus 12cm

Carolus 17cm

Piko 12cm

Piko 17cm

Xanthos12cm

Xanthos17cm



Cultivar´s growth habiterectophile versus planophile

11

Morphological differences in wheat varities

Plant height : Pegassos > Astron > Greif

Ground Cover (%) : Pegassos > Astron > Greif IOL

INSTITUT FÜR ORGANISCHEN LANDBAUUNIVERSITÄT BONN

Drews 1/03


0

20

40

60

80

100

120

Greif Astron Pegassos

Plant height (cm)

ac

b

0

20

40

60

80

100

120


Plant height (cm)

ac

b

a

0

20

40

60

80


Ground cover (%)

ba

c

a

0

20

40

60

80


Ground cover (%)

ba

c

Wheat cultivars: Light interception und weed ground cover (WG 2 - EC 55)

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Drews 1/03


60

70

80

90

100


PAR-Absorption (%)

ac b

60

70

80

90

100


PAR-Absorption (%)

ac b

0

2

4

6

8

10

12

14


Weed ground cover(%)

abb

a

0

2

4

6

8

10

12

14



abb

a

12

0

2

4

6

8

10

12

14



abb

a

0

2

4

6

8

10

12

14



abb

a

60

70

80

90

100


PAR-Absorption (%)

ac b

60

70

80

90

100


PAR-Absorption (%)

ac b

Wheat cultivars: Light interception und weed ground cover (WG 2 - EC 55)

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Drews 1/03


Cultivars´ effect on weed ground coverIOL- core trials, EC 49-65, five sites

* without KL 1 (63 % weed ground cover)

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a

0

5

10

15

20

25

WG 1 WG 2 VE 2 WG 3 LU 3


Weed ground cover (%)

a

ba

abab

ab

ab

ab a

bb

ab

Site:

a

0

5

10

15

20

25

WG 1 WG 2 VE 2 WG 3 LU 3



a

ba

abab

ab

ab

ab a

bb

ab

Site:

13

0

2

4

6

8

10

12

14

16

18

12 cm 24 cm



abb

a

n.s.

Row distance

Crop morphology: cultivar choice especially useful for

wide row distances (WG 2 - GS 55)

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Drews 1/03

pe


Cv. GreifCv. Pegassos

Different growth habits of winter wheat

Präsentation_Driebergen_Jan_2005.ppt CD 11/01/05

planophile erectophile


Row distance 24 cm

14

70

75

80

85

90

95

100

12 cm 17 cm 24 cm


Influence of row distance on the shading abilityof cultivars (WG 2 - EC 55)

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PAR-Absorption (%)

Row distance

Drews 1/03


70

75

80

85

90

95

100

12 cm 17 cm 24 cm


Influence of row distance on the shading abilityof cultivars (WG 2 - EC 55)

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PAR-Absorption (%)

Row distance

Drews 1/03


15

Ideotype Growth stage Row width Crop height LAI k (m) (m) (m2 leaf)/ (m2 ground) Planophile 13-21 0.05 0.04 0.3 1.20 31 0.09 0.20 0.9 1.14 49 0.13 0.60 3.5 0.67 65 0.24 0.85 4.5 0.66 Erectophile 13-21 0.03 0.06 0.3 1.00 31 0.06 0.30 1.2 0.95 49 0.10 0.80 4.0 0.61 65 0.15 0.85 5.5 0.63 Planophile2 13-21 0.05 0.04 0.3 1.20 31 0.09 0.20 1.2 1.14 49 0.13 0.60 4.0 0.67 65 0.24 0.85 5.5 0.66 Erectophile2 13-21 0.03 0.06 0.3 1.00 31 0.06 0.30 0.9 0.95 49 0.10 0.80 3.5 0.61 65 0.15 0.85 4.5 0.63

The row width, crop height, leaf area index (LAI) a nd extinction coefficients (k) for the ideotypes at the key growth stages


Topp et al 2004

Ideotype Growth stage Light intercepted by the crop (%)

12 cm 17cm 24 cm Planophile 13-21 0.06 0.04 0.03 31 4.07 2.88 2.05 49 47.62 36.08 25.71 65 88.89 89.00 89.09 Erectophile 13-21 0.07 0.05 0.03 31 4.62 3.28 2.33 49 54.08 38.16 27.11 65 100.00 91.92 65.20 Planophile2 13-21 0.06 0.04 0.03 31 6.19 4.38 3.12 49 55.67 42.19 30.06 65 100.00 100.00 100.00 Erectophile2 13-21 0.07 0.05 0.03 31 2.98 2.12 1.50 49 45.98 32.45 23.05 65 84.33 73.56 52.19

Topp et al 2004

The percentage of light intercepted by the crop at the key growth stages

16

Ideotype Growth stage Light intercepted by the crop (%)

12 cm 17cm 24 cm Planophile 13-21 0.06 0.04 0.03 31 4.07 2.88 2.05 49 47.62 36.08 25.71 65 88.89 89.00 89.09 Erectophile 13-21 0.07 0.05 0.03 31 4.62 3.28 2.33 49 54.08 38.16 27.11 65 100.00 91.92 65.20 Planophile2 13-21 0.06 0.04 0.03 31 6.19 4.38 3.12 49 55.67 42.19 30.06 65 100.00 100.00 100.00 Erectophile2 13-21 0.07 0.05 0.03 31 2.98 2.12 1.50 49 45.98 32.45 23.05 65 84.33 73.56 52.19

Topp et al 2004

The percentage of light intercepted by the crop at the key growth stages

Yield performance

Utilisation

Uptake

Drought resistance


Root surface

Rooting depth


Yield performance

Utilisation

Uptake

Drought resistance


Root surface

Rooting depth



I OLI OL

Target goals

Wax coating

Target area

Baking quality


Mycotoxins

Product quality

Shading ability


Soil covering

Tillering


Morphological

features

Plant height



Pathogenes

Septoria disease

Fusarium disease

Target goals

Wax coating

Target area

Baking quality


Mycotoxins

Product quality

Baking quality


Mycotoxins

Product quality

Shading ability


Soil covering

Tillering


Shading ability


Soil covering

Tillering


Morphological

features

Plant height



Pathogenes

Septoria disease

Fusarium disease

Plant height



Pathogenes

Septoria disease

Fusarium disease


17

Shoot morphology ( plant height) of spring wheat: Shading ability and weed pressure

0

20

40

60

80

EC 23 EC 31 EC 57 EC 74 EC 85

PAR (%)

cv „Star“ short

cv „Nandu“ long

Shoot morphology ( plant height) of spring wheat: Shading ability and weed pressure

0

20

40

60

80

100

EC 24 EC 31 EC 56 EC 75 EC 95

Weed mass (%)

(KORR et al. 1996)

18

IOL

Competitiveness during GS 31-75 influenced by shoot parameters:

• Crop ground cover• Shoot mass • LAI• Crop height • light interception

All negatively correlated with weed parameters.


Soil cover

Plant height

Shoot mass

LAI

EC 39

0.40***

0.44***

0.17

0.24*

Absorption PAR

EC 55

0.63***

0.54***

0.46***

0.53***

EC 32

0.65***

0.67***

0.57***

0.64***

n= 72 ; Siginificance: * α = 0.05 / ** α = 0.01 / *** α = 0.001

EC 65

0.57***

0.46***

0.34**

0.29*

Trial WG 1 Trial WG 2

EC 59

0.31**

0.40***

0.02

0.12

EC 32

0.57***

0.21

0.28*

0.35**

Trial VE 2

Winter wheat: correlation of light absorption and cro pmorphology

1/03


19


Relationship between crop ground cover (%) at EC50 and weed ground cover at EC50 (upper figure) and post-harvest (lower figure).

Crop ground cover (%) at EC50

Berdun Marius Texel

2nd Trial “La Bomba”

20

2002/2003

Cultivar

5,3 a4,5 b^^4,9 ab5,60 a4,09 b4,23 b32

Tillering (tillers/plant)4,5 a3,7 b4,5 a2,92 a2,46 b2,84 a67

37,6 b32,7 b63.8 a---67

124,4 b119,9 b153,2 a61,28 a56,67 b66,78 a32Weed Density (plants m-2)

35,67 a

44,41 a

902,34 b

430,35

4,45 a

6,18

68,67 a

42.97 b

-

92.83 b

-

61.72 a

Texel

22,01 b

25,28 b

950,49 a

548,53

3,83 b

5,95

66,54 b

54.24 a

-

94.50 a

-

62.15 a

Marius

20,13 b

22,98 b

982,19 a

523,35

3,80 b

5,91

54,39 c

42.58 b

-

88.87 c

-

50.41 b

Berdun

24,4 b20,7 b44,4 a67

28,2 b22,9 b41,6 a32Weed Biomass (g m-2)

1277,7 ab1346,7 a1233,7 b67

418,7 b481,9 a396,3 b32Crop biomass (g m-2 d.m.)

4,754,584,2367

6,91 a7,24 a5,95 b32LAI leaves

98,4 b106,4 a77,2 c67

40,4 b47,6 a34,6 c32Crop Plant Height (cm)

93,1 a92,2 a84,9 b67

94,2 b96,8 a91,9 c32Light Interception across(intercepted PAR (%))

55,5 a50,2 b43,1 c67

66,162,257,232Crop Ground Cover (%)

TexelMariusBerdun

2001/2002GS

2002/2003

Cultivar

5,3 a4,5 b^^4,9 ab5,60 a4,09 b4,23 b32

Tillering (tillers/plant)4,5 a3,7 b4,5 a2,92 a2,46 b2,84 a67

37,6 b32,7 b63.8 a---67

124,4 b119,9 b153,2 a61,28 a56,67 b66,78 a32Weed Density (plants m-2)

35,67 a

44,41 a

902,34 b

430,35

4,45 a

6,18

68,67 a

42.97 b

-

92.83 b

-

61.72 a

Texel

22,01 b

25,28 b

950,49 a

548,53

3,83 b

5,95

66,54 b

54.24 a

-

94.50 a

-

62.15 a

Marius

20,13 b

22,98 b

982,19 a

523,35

3,80 b

5,91

54,39 c

42.58 b

-

88.87 c

-

50.41 b

Berdun

24,4 b20,7 b44,4 a67

28,2 b22,9 b41,6 a32Weed Biomass (g m-2)

1277,7 ab1346,7 a1233,7 b67

418,7 b481,9 a396,3 b32Crop biomass (g m-2 d.m.)

4,754,584,2367

6,91 a7,24 a5,95 b32LAI leaves

98,4 b106,4 a77,2 c67

40,4 b47,6 a34,6 c32Crop Plant Height (cm)

93,1 a92,2 a84,9 b67

94,2 b96,8 a91,9 c32Light Interception across(intercepted PAR (%))

55,5 a50,2 b43,1 c67

66,162,257,232Crop Ground Cover (%)

TexelMariusBerdun

2001/2002GS

Core trial La Bomba (LB)Core trial La Bomba (LB)

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Generally:

Breeding programs performed under the typical (specific) growing conditions resulted in well adapted cultivars


21

IOL

Plant height (late phase)

• Tall plants often realize higher crop ground cover &higher competitiveness against tall weeds (grasses e.g. Br. tectorumor Apera spica ventii )

• Breeding progress based on increased harvest indexStraw needed in mixed farms for bedding Lower grain yield level not effected by straw-length

• Dwarf types less competitive for controlling weeds


Effect of variety height on undersown clover

relatively minor

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Trend for shorter cultivars to encourage clover biomass

D. YOUNIE


0.226.21.275.7Long

0.246.31.165.1Medium

0.345.91.455.1Short

Clover biomass

(kg D.M ha-1)

Grain yield 15%

D.M.(t*ha-1)

Clover biomass

(kg D.M ha-1)

Grain yield 15%

D.M.(t*ha-1)

Cereal strawlength

Spring oatsSpring barley

0.226.21.275.7Long

0.246.31.165.1Medium

0.345.91.455.1Short

Clover biomass

(kg D.M ha-1)

Grain yield 15%

D.M.(t*ha-1)

Clover biomass

(kg D.M ha-1)

Grain yield 15%

D.M.(t*ha-1)

Cereal strawlength

Spring oatsSpring barley

22

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Grain yield

• Planophile types can realize higher flag leaf area resulting in higher photosynthesis rate and yield performance also with low LAI

• should be based on high 1000-seed weight

Bigger grains result in competitive vigorous seedlings as a function of

• earlier emergence • higher root-length density, root surface • seed health enhanced


Weed competitiveness as influenced by seed size

30

25

20

15

10

5

014 Apr 9 Juneth 17 Juneth 13 July

LSD 10%

LSD 5%

n.s.

% Weed covering

Seed size >2.5 mm

Seed size >3.0 mm

Seed quality

Seed size >2.5 mm

Seed size >3.0 mm

Seed quality


23

150

250

300

350

400

3.5 4.0 4.5 5.0 5.5

2 - 2.5

2.5 - 2.75

2.75 - 3

> 3

2 - 2.5

2.5 - 2.75

2.75 - 3

> 3

See

dsi

zein

mm

See

ding

den

sity

/m²

LSD 5%

LSD 5%

t * ha-1(PIORR 1991)

Winter wheat c.v. Granada: grain yield as affected by seed size and seeding density


Problem weeds


24

Galium aparine as affected by winter wheat cultivarsSperber (erectophile) and Granada (planophile)

EISELE 1992

Effects by shading I

05

10152025303540


Blütentriebe/m²

n.s.Galium aparine

• Scrambling weed

Shading sensitivity: low

(corr. with wheat -PAR: r= -0.08)

• But: sensitivity high in dry soil (dwarf G. aparine plants) (SEAVERS & WRIGHT 1999)

• Scrambling weed

Shading sensitivity: low

(corr. with wheat -PAR: r= -0.08)

• But: sensitivity high in dry soil (dwarf G. aparine plants) (SEAVERS & WRIGHT 1999)

0

510

15

20

2530

35

40


Rispen/m²

ab b

0

510

15

20

2530

35

40


Rispen/m²

ab b

EC 55

EC 71

Drews 1/03


• Shorter than wheat during vegetative growth, flowering shoots higher

• Long vegetative phase, late floering

shading sensitivity: high

(corr. mit wheat-PAR: r= -0,41***)

• Shorter than wheat during vegetative growth, flowering shoots higher

• Long vegetative phase, late floering

shading sensitivity: high

(corr. mit wheat-PAR: r= -0,41***)

Apera spica-venti

25

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II

⇒ sensitivity to shading: f ( plant height of weed relat ive to wheat

a

0

5

10

15

20

25

30


a

b

c

Blütenköpfchen/m²

a

0

5

10

15

20

25

30


a

b

c

Blütenköpfchen/m² Matricaria recutita

• Shorter than wheat during vegetation time

Shading sensitivity : high (corr. With wheat – PAR: r= -0.62***)

• Shorter than wheat during vegetation time

Shading sensitivity : high (corr. With wheat – PAR: r= -0.62***)

EC 55

Drews 1/03


Effects by shading

Bewertung der beiden Standard-Winterweizensorten ‘B atis’ und ‘Ritmo’nach Angaben in der Beschreibenden Sortenliste

Quelle: NIEMANN, P., BBA-Berichte, Heft 72 - 2000Bewertung Batis und Ritmo.cdr, FT, 4.12.00

Merkmal Batis Ritmo

Vermehrungsfläche 1998 3.800 ha (3. Sorte) 7.300 ha (1. Sorte)

Qualitätsgruppe A B

Kornertrag 6 7

Mehltauanfälligkeit 3 5

Lagerneigung 5 3

Tausendkorngewicht 7 5

Auswinterungsneigung 5 3

Unkrautunterdrückung 1) 8 4

1) nach eigenen Bonitierungen (NIEMANN, 2000)

(BUNDESSORTENAMT, 1999)

26

Bewertung der interspezifischen Konkurrenzkraft von Winterweizensorten nach verschiedenen Kriterien

Quelle: NIEMANN, P., BBA-Berichte, Heft 72 - 2000interspezifische Konkurrenzkraft.cdr, FT, 4.12.00

Sorte Deckungsgrad Höhe Wachstum Note

Orestis ++ 0 + ++

Pagode ++ 0 - ++

Obelisk ++ 0 + ++

Boheme + 0 + +

Rektor + 0 0 +

Astron + 0 0 +

Kanzler 0 + 0 0

Andros + 0 0 0

Contra 0 - + 0

Tristan 0 + 0 0

Sperber -- + 0 -

Kraka -- + - -

Slejpner - -- - --

+ hohe, 0 mittlere, - niedrige Ausprägung

(VERSCHWELE und NIEMANN, 1993)

Target goals

Wax coating

Target areaBaking quality


Mycotoxins

Product quality

Yield performance

Utilisation

Uptake

Drought resistance


Root surface

Rooting depth


Shading ability


Soil covering

Tillering


Morphological

features

Plant height



Pathogens

Septoria disease

Fusarium disease

Cereal ideotypes (Wheat) for Organic Agriculture

27

Plant health / resistance - quality


Produktqualität


28

Infection of the flag leaf with Septoria nodorumEC 63 - 67 (r) EC 74 - 76 (r)-0,34 -0,40

-0,64** -0,71**

-0,52** -0,61**

Insertion heigt FlagleafDistance 2. Leaf - FlagleafDistance 3. Leaf - Flagleaf

Resistance: shoot morphology prevents ear diseases


Distance ear - flag-leaf (cm)

Fus

ariu

m+M

.niv

ale

(% in

fest

. gra

in)

Fusarium spp and Microdochium nivale:Grain infestation as a function of the ear to flag-leaf distance


29

0

10

20

30

40

50

60

0

10

20

30

40

50

60

INT INT+F OA INT OA0

100

200

300

400

500

600

0

100

200

300

400

500

600

INT OA INT OA

Deo

xyni

vale

nol

[ µg/

kg T

M ] DON-Fusarium spp.Fusarium spp.

1997

INT+F

1998INT+F1997

INT+F1998

0

10

20

30

40

50

60

0

10

20

30

40

50

60

INT INT+F INT

Infe

sted

grai

ns[ %

]

0

100

200

300

400

500

600

0

100

200

300

400

500

600

INT INT

Deo

xyni

vale

nol

DON-content

1997

INT+F

1998INT+F1997

INT+F1998

OA= Organic Agriculture Int= Integrated Agriculture +F= Fusarium-Fungicide applied

Fusarium infestation and Deoxynivalenol (DON) mycotoxin content of winter wheat grains derived from organic and int egrated cultivation

Fusarium Fusarium infestedinfested grainsgrains and DON and DON contentcontent LowerLower in Organic Agriculturein Organic Agriculture


IOL

Breeding aim: Leaf area duration (LAD)

Accounting for about half of the variation in grain yields performed by

• healthy cultivars ( leaf diseases ,e.g. DTR)• Nitrogen efficency (utilization)• Extended ‘post-floral phase’


30

Thank you

for your attention !

Reunion FSOV Adventice September 17, 2007, Paris, Fr ance

www.iol.uni-bonn.de

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