S. Kumudini, C. Godoy, J. Board, S. Kumudini, C. Godoy, J. Board, and J. Omielanand J. Omielan

Developing a Yield Loss Prediction Model for Asian Soybean Rust; A Crop Physiology Approach

OutlineMultidisciplinary study - Develop yield loss prediction modelYield equationHow does SBR impact soybean yield

Study – the role of defoliation injuryStudy – the impact of SBR lesions on plant productivity

Summary

Rust causing premature defoliation

Pirapó, Paraguay – 2001

TreatedTreated ControlControl

MATO GROSSO, Brazil

ChallengeDevelop a yield loss prediction model for soybean rust

Project Website

Objective

To develop yield loss prediction model for soybean rust

Yb = ∫ (Q X Ia X ε) dt

Yg = Yb X HI

Yield

ObjectivesObjectives

I. Check assumption: Is SBR-induced yield loss due to defoliation injury?

II. Model building: Develop a model that can effectively predict SBR-induced yield loss

Yb = ∫ (Q X Ia X ε) dt

Embrapa Soja, Londrina, Brazil

Objective: Determine the role of defoliation injury on SBR-induced yield loss

Role of Defoliation injury in yield loss? Londrina, Brazil

04 February 2006First flower

Cultivar BRS 154 (MG VII) Rows 45 cm (~18 inches)Planted 20 December, 2005

1 st. fungicide application 02 February 2006 (Tetraconazole - Eminent 0.4L/ha - marketed in US as Domark)

Materials and Methods

RCBD design, 6 replicationsFive treatments

1. SBR - R1

Materials and Methods

RCBD design, 6 replicationsFive treatments

1. SBR - R12. Mimic “SBR” at R1

Materials and Methods

RCBD design, 6 replicationsFive treatments

1. SBR - R12. Mimic “SBR” at R13. SBR - R5

Materials and Methods

RCBD design, 6 repsFive treatments

1. SBR - R12. Mimic - R13. SBR - R54. Mimic - R5

Materials and Methods

RCBD design, 6 repsFive treatments

1. SBR - R12. Mimic - R13. SBR - R54. Mimic - R55. Control

Materials and Methods

Measured Leaf Area IndexDisease severityYield

Results and Discussion

Disease severity over time

0102030405060708090

100

40 50 60 70 80 90 100

Days After Planting (d)

Dis

ease

Sev

erity

(%)

ControlSBR at R1Mimic SBR at R1SBR at R5Mimic SBR at R5

R5R1

Plants infected at R1, leaf area over time

R2 = 0.94

R2 = 0.96

R2 = 0.92

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

45 55 65 75 85 95Days After Planting (d)

Leaf

Are

a In

dex

(m2 m

-2)

Control

SBR at R1

Mimic SBR at R1

R5R1

Plants infected at R5, leaf area over time

R5R1

R2 = 0.99

R2 = 0.96

R2 = 0.98

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

45 55 65 75 85 95Days After Planting (d)

Leaf

Are

a In

dex

(m2 m

-2)

Control

SBR at R5

Mimic SBR at R5

Role of defoliation injury in yield loss?

VS.

SBR-infected plot (SBR at R1) Mimic SBR at R1Fungicide treated, and manually defoliated to mimic SBR- plots

Plants at R5

Role of defoliation injury in yield loss?

VS.

Mimic SBR at R1Fungicide treated, and manually defoliated to mimic SBR- plots

SBR-infected plot (SBR at R1)

Plants around R6

Impact of SBR on yield

0

500

1000

1500

2000

2500

SBR at R1 SBR at R5 Control

Yiel

d (k

g ha

-1)

SBR Manual defoliation

Yield

Ye = Yb X HI

Yb = ∫ (Q X Ia X ε) dt

Relationship between LAD and yield

R2 = 0.4821ns

0

20

40

60

80

100

120

140

0 20 40 60 80 100 120

Leaf Area Duration (m2 d)

Yiel

d (g

m-2

)

1 year dataAssumption SBR-induced yield loss due to defoliation injury ?

VS.

SBR- plots at R6 (infected at R1) Fungicide treated, and manually defoliated to mimic SBR- plots

Close look at SBR-infected plot

Non-abscised SBR-infected leaf

Healthy leaf area index (HLAI)HLAI = LAI minus % diseased leaf area

Relationship between healthy leaf area index (HLAI) and yield

R2 = 0.7492*

0

20

40

60

80

100

120

0 20 40 60 80 100 120

Healthy Leaf Area Duration (m2 d)

Yiel

d (g

m-2

)

What is the role of necrotic lesions on plant productivity?

Objective: Impact of SBR Lesions on plant productivity

Preliminary study in Quincy FloridaNorth Florida Research and Education Center

Cultivar DP 72200-RRRow widths 36”Fungicide: Headline SBR

MeasurementsSelected leaves that showed a variation in disease severity

2nd or 3rd central trifoliolate from the topMost control were obtained from fungicide treated plotsHigh disease severity were obtained from non fungicide treated plots

Growth stage R6Net photosynthetic rate

400 CO2 reference side1500 µmoles m-2s-1 (PPFD)30oC temperature

Results and Discussion

W10 100%100% Full photosynthetic capacity

– 75%75% Full photosynthetic capacity

% of healthy leaf (x9) 50% Full photosynthetic capacity

w300 = 35% of healthy leaf35% Full photosynthetic capacity

X20 = 1% of healthy leaf3% Full photosynthetic capacity

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

Rel

ativ

e Ph

otos

ynth

etic

rate

(%)

0 0-1% 2-3% 4-5% 6-7% 8-9% 10-11%

12-14%

20-21%

Necrotic lesions (% of area)

Impact of necrotic lesions on photosynthesis

Impact of SBR Lesions on plant productivity (preliminary)

SBR-induced necrotic lesions reduce plant productivity, and will likely be important in yield reduction

Impact of SBR lesions on plant productivity appears to be GREATER than that due to reduced light interception alone.

SummarySBR-induced yield loss was dependent on plant growth stage

SBR can cause severe defoliation injury and even limit achievement of maximum LAI

Lesions on non-abscised leaves have an important impact on yield

0

500

1000

1500

2000

2500

SBR at R1 SBR at R5 Control

Yiel

d (k

g ha

-1)

SBR

R2 = 0.94

R2 = 0.96

R2 = 0.92

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

45 55 65 75 85 95Days After Planting (d)

Leaf

Are

a In

dex

(m2 m

-2)

Control

SBR at R1

Mimic SBR at R1

Overall Summary

Based on 1 year of data

Yield is a function of healthy leaf area duration

Yield loss models must account for both defoliation injury and rust-induced lesions on non-abscised leaves

R2 = 0.7492*

0

20

40

60

80

100

120

0 20 40 60 80 100 120

Healthy Leaf Area Duration (m2 d)

Yiel

d (g

m-2

)

Acknowledgments

Funding USDA, Risk Mangement AgencySouthern Soybean Research Program

Project website:http://www.uky.edu/Ag/Agronomy/Department/sbr/index.htm