Enhancing food security through improved seed systems of appropriate cassava, resilient to climate...
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Transcript of Enhancing food security through improved seed systems of appropriate cassava, resilient to climate...
ENHANCING FOOD SECURITY THROUGH
IMPROVED SEED SYSTEMS OF APPROPRIATE
CASSAVA, RESILIENT TO CLIMATE CHANGE IN
EASTERN AFRICA
Baguma Yona, Nuwamanya Ephraim, Magambo Stephen and Akoli Barbara
First Bio-Innovate Regional Scientific ConferenceUnited Nations Conference Centre (UNCC-ECA)
Addis Ababa, Ethiopia, 25-27 February 2013
Field screening of cassava for combined tolerance to elevated atmospheric
temperature and low soil moisture and farmer preferred attributes
Understanding the basis of tolerance
Morphological
• Leaf characteristics: Measurable/Observable
• Stem characteristics: Measurable/Observable
•Root characteristics: Measurable/Observable
•Others
Biochemical
•Photosynthetic enzymes assay
•Anti oxidant enzymes assay
•Carbohydrate and amino acid analysis
•Hormone and secondary metabolites
Physiological
•Photosynthetic capacity assessment
•Nutrient allocation studies
•Osmotic adjustment studies
•Transpiration mechanisms
•Water relations
Genetic
•Microarray analysis
•Gene chip analysis
•Quantitative reverse transcriptase PCR
•Others
3/4/2013 3
Newport Scientific Pty Ltd0
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Graphical Analysis Results - 20081010
Objectives
• Main Objectives To identify cassava varieties that are tolerant to moisture and heat stress
and understand mechanisms behind observed tolerance and /or resistance.
• Specific objectives1. Screen Ugandan cassava germ-plasm for accessions with tolerance to low
moisture stress
2. Screen Ugandan cassava germ-plasm for accessions with tolerance to elevated heat
3. Determine the effect of elevated heat, low moisture stress and their interaction on yield and yield components of cassava
4. Elucidate the genetic and biochemical basis of tolerance to heat and moisture stress in cassava
Materials and experimental Layout
• 20 Cassava varieties selected from different parts of country (Cassava selections for drought tolerance study.doc)
• Field experiment was set up in Kasese Western Uganda (Gmap Kasese)
• Expt Design: RCBD with 4 replications, 2 stressed and 2 control (irrigated) (exptal layout)
Results• Phenotypic data (collected on a bimonthly
basis) and spectral data (daily for 2 weeks) from trial
• Corresponding biochemical and physiological data was taken on leaves
• These datasets are being validated in second season trial
Grouping of varieties• Depending on their phenotypic and physiological
reaction to stress, varieties were grouped into those that
– Maintained a higher leaf area index (LAI) throughout stress as stay green varieties (SGV)
– Regained at least half of total number of leaves immediately after stress or early recovering varieties (ERV)
– Did not recover at all or took a long time to recover Susceptible varieties (SV)
Difference in cumulative leaf number observed for the twenty varieties
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-50
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400
Variations in leaf reflectance for variety groups
Variety Groups Intensity 09:00Hrs 12:00Hrs 15:00Hrs
Stay green Red (%) 30.99 29.84 29.57
Green(%) 43.89 42.04 42.83
Blue(%) 25.31 28.12 27.59
Av. Intensity 0.523 0.538 0.537
Early Recovery Red (%) 31.81 30.19 30.69
Green(%) 42.81 44.54 43.05
Blue(%) 25.36 25.27 26.26
Av. intensity 0.531 0.501 0.520
Susceptible Red (%) 31.07 30.30 29.38
Green(%) 42.43 42.63 42.73
Blue(%) 26.51 27.08 27.89
Av. Intensity 0.548 0.495 0.559
From 7-9 leaf lobes before the onset of stress to 5-4 leaflobes on mild stress, to 3-2-1 or
sometimes deformed at maximum stress and to leafless stems in some varieties on some
instances . This was followed by increase in sugar
concentration and secondary metabolites such as phenolics and tannins. Differences were
observed in the different varieties for all these properties
One of the methods used in selection was leaf lobe retention!!!!
6MAP
10MAP
9MAP
8MAP
Differences in the rates of recovery observed
y = 0.02x + 0.357R² = 0.477
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0.5
RS1(Wk1) RS2(WK3) RS3(WK5) RS4(WK7
A
y = -0.0718x + 0.6025
R² = 0.1433
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0.8
0.9
RS1(Wk1) RS2(WK3) RS3(WK5) RS4(WK7
B
y = 0.1104x + 0.2565
R² = 0.9271
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0.5
0.6
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0.8
RS1(Wk1) RS2(WK3) RS3(WK5) RS4(WK7
C y = -0.005x + 0.407R² = 0.016
0
0.05
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0.15
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0.25
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0.35
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0.45
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RS1(Wk1) RS2(WK3) RS3(WK5) RS4(WK7
D
A=Changes in Reducing Sugars among stay green varieties B=Changes in Reducing Sugars for Early recovering varieties C=Changes in Reducing Sugars for susceptible variety. D=Changes in reducing Sugars for all the varieties
Results: Free Reducing Sugars (RS)
Changes in Cyanide Content
y = 0.025x + 0.633R² = 0.016
y = -0.013x + 0.423R² = 0.023
0
0.2
0.4
0.6
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MC(WK1) MC(WK3) MC(WK5) MC(WK7) MC(WK9)
A
y = 0.0713x + 0.3497
R² = 0.1758
y = -0.003x + 0.399R² = 0.002
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0.2
0.4
0.6
0.8
1
1.2
MC(WK1) MC(WK3) MC(WK5) MC(WK7) MC(WK9)
B
y = -0.1034x + 0.9402
R² = 0.1097
y = -0.042x + 0.432R² = 0.108
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0.4
0.6
0.8
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1.2
1.4
1.6
MC(WK1) MC(WK3) MC(WK5) MC(WK7) MC(WK9)
C
y = -0.004x + 0.703R² = 0.000
y = -0.027x + 0.347R² = 0.093
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0.4
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0.8
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1.4
1.6
1.8
MC(WK1) MC(WK3) MC(WK5) MC(WK7) MC(WK9)
D
CnP Peel
A=Cyanide changes for all varieties throughout the stress period, B=Cyanide Change for stay green varieties, C= Cyanide change for early recoveringvarieties, D=Cyanide change for susceptible variety
Total Pigments; Chla, Chlb, Cart
y = 0.021x + 0.151R² = 0.732
y = 0.005x + 0.079R² = 0.300
y = -0.020x + 0.464R² = 0.324
0
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Harvest1 Harvest 2 Harvest 3 Harvest 4
Total pigment content
y = 0.013x + 0.176R² = 0.547
y = 0.004x + 0.080R² = 0.128
y = -0.040x + 0.514R² = 0.680
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Harvest1 Harvest2 Harvest 3 Harvest 4
Pigments for stay greens
y = 0.045x + 0.072R² = 0.977
y = 0.015x + 0.042R² = 0.961
y = 0.025x + 0.313R² = 0.868
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0.45
Harvest1 Harvest2 Harvest 3 Harvest 4
Graph for early recovering genotypes
y = 0.007x + 0.169R² = 0.029
y = 0.000x + 0.084R² = 0.000
y = -0.014x + 0.446R² = 0.045
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Harvest1 Harvest2 Harvest 3 Harvest 4
Pigments for susceptible
Chla
Chlb
cart
Changes in carbohydrate Profiles
y = 0.012x + 0.156R² = 0.308
y = 0.039x + 0.174R² = 0.432
y = -0.017x + 0.15R² = 0.6
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Harvest 1 Harvest 2 Harvest 3 Harvest 4
Total carbohydrate metabolite changes
y = 0.023x + 0.138R² = 0.377
y = 0.009x + 0.251R² = 0.015
y = -0.023x + 0.164R² = 0.743
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Harvest 1 Harvest 2 Harvest 3 Harvest 4
Carbohydrate profiles for Stay green
y = -0.011x + 0.197R² = 0.474
y = -0.006x + 0.216R² = 0.067
y = -0.013x + 0.126R² = 0.634
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0.05
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Harvest 1 Harvest 2 Harvest 3 Harvest 4
Carbohydrate profile for Early recovering
y = 0.015x + 0.162R² = 0.291
y = -0.005x + 0.278R² = 0.002
y = -0.016x + 0.137R² = 0.502
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0.05
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0.35
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0.45
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Harvest 1 Harvest 2 Harvest 3 Harvest 4
Carbohydrate profiles for susceptible varieties
Free RS
Bound RS
Starch Content
Recovery after stress: Understanding the mode ???
The phenomena was observed in 266 BAM and 72-TME 14 earlier even before the rains set in. By the time of harvest (12MAP), plants had already achieved leaf numbers higher than earlier
observed although massive remobilization of carbohydrates was observed in their roots. All
varieties had a recovery mechanism. Difference was in the time of recovery after stress !!!
The selection criteria
• A combination of phenotypic, physiological , spectral and biochemical indicators have been used
• These include
– Plant growth height and leaf/leaf lobe retention
– Diurnal changes in pigment concentration (esp chla)
– Relationships between absorbed spectra and pigment concentration (Diurnal changes in these)
– Carbohydrate metabolism
– Secondary metabolite changes
Some of the selected varieties at the end of peak stress
NASE 2 0686MH97/0067
266 BAM
NASE 1
72-TME 14
Stay green varieties
Early recovering varieties
Typical susceptible variety