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UMR Environnement et grandes cultures (EGC)
INRA Grignon , France

Effects of septoria on nitrogen metabolism
and senescence in french bread wheat
during grain filling
Ben Slimane Rym

Septoria workshop
20-28 april 2015

Agronomic context
N Fertilisation
(Late application of
N fertilizers)

Lowering the use of pesticides
Wheat quality (%Pi)
Late foliar diseases
Septoria leaf blotch

Septoria damage
When the 3 uppermost leaves are
attacked at the end of stem extension

Improving grain protein
content

Context: increasing inputs Vs late foliar diseases (Septoria)

The need for a reliable prediction of damages caused by
the pathogen (Zymoseptoria tritici)
The need for a solid knowledge of the effects of pathogens
on crop functionning in a modelling scheme

Joint use of experiments and modelling
Collaboration

Studying processes

Rym Ben Slimane
Pierre Bancal
Marie-Odile Bancal

Research

• Decorrelation
• Hierarchical classification
•Integration in models

Identification of key elements

Experiments at a big scale
Operational recommendations
Integration in models

Development
Philippe Gate

Modelling septoria damage
Quantitative damage

Qualitative damage

Biomass loss/ yield loss

Quality loss (protein content)

Modelling in progress
Published studies

Lack of understanding
Protein content : N/C

(Shtienberg, 1992; Cornish et al.,
1992; Robert et al., 2004)

N

or

(Dimmock et
Gooding,2002)

C

To clarify the effects of septoria on N metabolism in order to
elaborate a model of N functioning in diseased plants

N functionning and senescence in healthy and diseased plants
during grain filling
Healthy plant (case of wheat)

Septoria tritici
Grain N

N Remobilisation

+

(from vegetative organs)

(70%)

Leaf senescence



Post-anthesis N Absorption
(20-30%)

Green leaf area

Apical senescence
?
Decorrelation

Disease symptoms

2. Effect of septoria disease on the determinants of
nitrogen grain filling in wheat
Septoria tritici
Grain N
N Remobilisation
(from vegetative organs)

+

(70%)

Post-anthesis N Absorption
(20-30%)

 Working separately on the different vegetative organs:
Leaves, sheaths, stems, glumes
 Working per leaf layer
 Working with kinetics instead of the balance method

Outline
1. Effects of septoria disease on apical senescence
2. Effect of septoria disease on the determinants of
nitrogen grain filling in wheat
3. Which gains for nitrogen flux modelling in diseased
plants?
4. Remaining questions upon the mode of action of
septoria disease on the host N metabolism

1. Effects of septoria disease on apical senescence
Varieties * isolates

Inoculation of L1 in greenhouse
2 cm²
105
spores/ml

Soissons

Apache

Caphorn

Koréli

i1

++++

++++

+++

+

i2

++++

++++

+++

+

i3

++++

+++

+

+

i4

+

+

-

-

Inoculation of L1 and L2 in natural conditions
Susceptible variety: Soissons

•Increasing the inoculated surface

One isolate

•Inoculum concentration= 106 spores/ml

Dose and dates of N fertilisation

7

6

6

5

2008.1
2008.2

5

[N] (%MS)

GLAI (m2/m2)

Natural epidemics

4
3
2
1

2008.3

4
3
2
1
0

0

GLAI

[N] F1

[N] F2

Non destructive monitoring

1153 °j

1058 °j

1003 °j

932 °j

768 °j

636 °j

Artificial inoculations

512 °j

405 °j

1. Effects of septoria disease on apical senescence

Evolution of apical
senescence

Evolution of
inoculated region

Natural epidemics
Evolution of an inoculated leaf in greenhouse

Destructive monitoring
Weekly sampling of
average plants

Scanning the leaves

Image analysis

Is apical senescence accelerated by septoria disease?
Kinetics of senescence and
disease

Correlation between the rates of apical
senescence and disease surfaces

S malade
S apicale

0,8%
0,7%

Surface sénescente (%Stot)

40%

Logistic Adjustement
Disease S.: y=M/(exp(r*(t-T))
Exponential Ajustement
Apical S.: y= a.exp(R.t)

30%
20%
10%
0%
0

200

400

600

800

1000 1200

t (°j post inoculation)

Taux de Sapi (%dj-1)

50%

0,6%

r2=0.07

A
C
K
S

0,5%
0,4%
0,3%
0,2%
0,1%
0,0%
0,0%

1,0%
2,0%
3,0%
Taux de S. malade (%dj)

Non significant Relationship
Apical senescence is not accelerated by septoria disease
We can exclude acceleration of apical senescence in the
modelling framework of N fluxes (N remobilisation) in
diseased plants

2. Effect of septoria disease on the determinants of nitrogen
grain filling in wheat
Experiment in natural conditions
2

bread wheat varities: Soissons, Bastide

rates of N fertilisation

2008.2

6

5

5
4
3
2
1
0

2008.3

4
3
2
1
0

GLAI

 2 levels

2008.1

6

[N] (%MS)

 Variation of dates and

GLAI (m2/m2)

7

[N] leaf 1

of disease: treated or not against septoria

Sampling from heading to maturity
Measurements
 Green leaf area
 Total N in all organs: leaves, stems, sheaths, grains
 Enzymatic dosage from leaves: GS, NR, GDH, endoproteases

[N] leaf 2

Dividing the effect of septoria disease on green leaf area into phases

L2

Defining the phases from a
new creterion
L3

L4

Phase 1: diseased S. < 15%
Phase 3: green area (NT) # 0%

Phase delay


Delay of senescence
between leaf layers

S verte (cm² /brin)

20

1

10

3

2

0
0

200 400 600 800

40
S verte (cm² /brin)

L1

Leaf 1

30

-200

Leaf 2

30
20

3

2

1

10
0

-200

0

200 400 600 800

40
S verte (cm² /brin)

Loss of green leaf area

Indicator of disease development

40

Leaf 3

2

30

3

20
10
0

-200

0

200 400 600 800

40
S verte (cm² /brin)

Soissons ITK 2008.3 depending on the leaf layer

Leaf 4

30
20

2

3

10

-200

0
0

200 400 600 800

*1: no difference
*2: a more speedy decrease in
diseased leaves
*3: N blocked in diseased leaves

6
4
T
2

NT

0
0

200

400

600

800

t (°j post floraison)

N feuille 2 (mg/brin)

Three phases of the N decrease in diseased
leaves in comparison to healty ones

N F1

8

-200

N F2

8
6
4
2
0

- 200

0

200

400

600

800

t (°j post floraison)

N feuille 3 (mg/brin)

The defined phases from green area
could be applied to N kinetics per
leaf layer

N feuille 1 (mg/brin)

Dividing the effect of septoria disease on N kinetics into phases

N F3

8
6
4
2
0

-200

0

200

400

600

t (°j post floraison)

800

From all vegetative parts, only leaf nitrogen was affected by septoria
disease
12

Leaf N
N des balles (mg/brin)

N des feuilles (mg/brin)

20

15

10
T
5

NT

0

-200

0

200

400

600

8
6
4
2
0

-200

800

Glume N

10

0

200

t (°j post floraison)

10

Stem N

septoriose

0
0

200

400

600

800

t (°j post floraison)

N des gaines (mg/brin)

N des tiges (mg/brin)
-200

6

2

600

800

Sheath N

8

8

4

400

t (°j post floraison)

-200

6

4

2

0
0

200

400

600

800

t (°j post floraison)

In diseased plants, grain nitrogen is reduced at the end of grain filling
Leaf N
Grain N
15

2

50
10

N des grains (mg/brin)

N des feuilles (mg/brin)

20

T
5

NT

0

-200

0

200

400

600

800

t (°j post floraison)

3

40
30
20
T
10

NT

0
200

0

200

400

600

t (°j post floraison)

N des p.a ériennes (mg/brin)

Post-anthesis absorption

-200

60
55
50

septoriose

45
40
T

35

NT

30
25
0

200

400

600

800

t (°j post floraison)

800

At the metabolic level…
AA
αKG

transaminases
Glu GOGAT
LATS

NR
NO3-

NiR
NO2NH4+

Glu

αKG

Gln
GS2

GDH

Proteins

?

NH4+

Proteases
Amino acids

Gln
AA translocation

IHATS

Vegetative stage / N Assimilation

Glu
GS1

New cytosolic
GS

Senescence / N Remobilisation

NR, GS (GS1, GS2), GDH, proteases
good metabolic indicators of the impact of foliar diseases on N metabolism

How do these indicators behave in the case of septoria leaf blotch?

Effects of septoria on nitrogen metabolism indicators in leaves
Soissons and Bastide for all leaves per ITK
N total
GS
GDHd
Proteases
NR

=
=
=
>
<
S1 S2 S3 B1 B2 B3
---------- Phase 1 ----------

<
<
<

>

S1 S2 S3 B1 B2 B3
---------- Phase 2 ----------

>

<
<
=

S1 S2 S3 B1 B2 B3
---------- Phase 3 ----------

3. Which gains for nitrogen flux modelling in diseased plants?
0-50%: Post-anthesis absorption
Early decrease of NR activity in diseased leaves

Grain N

50-100%: N Remobilisation

N in leaves (mg/culm)

Defining phases of N fluxes in vegetative organs under
septoria disease (total N; metabolic indicators)
T
NT

15
10
5
0
0 200 400 600 800
Time (°Cd after anthesis)

Apical senescence not accelerated by septoria disease

4. Remaining questions upon the mode of action
of septoria disease on the host N metabolism
 Decrease of apparent absorption in phase 2 and 3
But
 Decrease of NR activity since phase 1
What about the other assimilation enzymes involved in
phase 2 and 3?
 N blockage in leaves
•Plant N not available?
• N assimilated by the fungus?
• Fungal enzymatic activities?

4. Remaining questions upon the mode of action of
septoria disease on the host N metabolism
Leaf senescence



Green leaf area

Apical senescence
?
Decorrelation

Disease symptoms

? local senescence +

Pycnidia

Merci de votre attention

5. Which perspectives in the case of Tunisia?



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