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 Conference
United 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
• Leaf characteristics: Measurable/Observable
• Stem characteristics: Measurable/Observable
Morphological
• Root characteristics: Measurable/Observable
• Others
Graphical Analysis Results - 20081010
320
100
• Photosynthetic enzymes assay 900
Viscosity RVU
240
Speed RPM
Temp 'C
80
• Anti oxidant enzymes assay 160
600
60
Biochemical • Carbohydrate and amino acid analysis 80
300
40
• Hormone and secondary metabolites 0
0 5 10 15
Time mins
Newport S c i enti fi c P ty Ltd
20 25
• Photosynthetic capacity assessment
• Nutrient allocation studies
• Osmotic adjustment studies
Physiological
• Transpiration mechanisms
• Water relations
• Microarray analysis
• Gene chip analysis
• Quantitative reverse transcriptase PCR
Genetic • Others
3/4/2013 3

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 objectives
1. 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
400
350
300
250
200
150
100
50
0
-50
-100
-150

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

One of the methods used in selection was leaf lobe retention!!!!
8MAP
6MAP
9MAP
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 10MAP
observed in the different varieties for all these
properties

Differences in the rates of recovery observed

Results: Free Reducing Sugars (RS)
0.5 A 0.9 B
0.8
0.4 0.7
y = 0.02x + 0.357
0.6 y = -0.0718x + 0.6025
0.3 R² = 0.477
0.5 R² = 0.1433
0.4
0.2
0.3
0.1 0.2
0.1
0 0
RS1(Wk1) RS2(WK3) RS3(WK5) RS4(WK7 RS1(Wk1) RS2(WK3) RS3(WK5) RS4(WK7
0.8 0.5
C y = 0.1104x + 0.2565
D y = -0.005x + 0.407
0.7 0.45 R² = 0.016
R² = 0.9271 0.4
0.6
0.35
0.5 0.3
0.4 0.25
0.3 0.2
0.15
0.2
0.1
0.1 0.05
0 0
RS1(Wk1) RS2(WK3) RS3(WK5) RS4(WK7 RS1(Wk1) RS2(WK3) RS3(WK5) RS4(WK7
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

Changes in Cyanide Content
1.2 B
1.4 A
1.2
1
y= 0.0713x + 0.3497
y = 0.025x + 0.633 R² = 0.1758
0.8
1 R² = 0.016
0.8 0.6
0.6 0.4
0.4 y = -0.003x + 0.399
0.2
R² = 0.002
y = -0.013x + 0.423
0.2
R² = 0.023 0
0 MC(WK1) MC(WK3) MC(WK5) MC(WK7) MC(WK9)
MC(WK1) MC(WK3) MC(WK5) MC(WK7) MC(WK9)
1.6 C
1.8 D
1.4
1.6
1.2 1.4
y = -0.004x + 0.703
1 1.2 R² = 0.000
y=- 0.1034x + 0.9402 1
0.8 R² = 0.1097 CnP
0.8 Peel
0.6 0.6
y = -0.027x + 0.347
0.4 0.4 R² = 0.093
y = -0.042x + 0.432
R² = 0.108 0.2
0.2
0
0 MC(WK1) MC(WK3) MC(WK5) MC(WK7) MC(WK9)
MC(WK1) MC(WK3) MC(WK5) MC(WK7) MC(WK9)
A=Cyanide changes for all varieties throughout the stress period, B=Cyanide Change for stay green varieties, C= Cyanide change for early recovering
varieties, D=Cyanide change for susceptible variety

Total Pigments; Chla, Chlb, Cart
0.6
Pigments for stay greens
0.5 Total pigment content
0.45 0.5
y = -0.020x + 0.464
y = -0.040x + 0.514
0.4 R² = 0.324
R² = 0.680
0.4
0.35
0.3
y = 0.021x + 0.151 0.3
y = 0.013x + 0.176
0.25 R² = 0.732
R² = 0.547
0.2 0.2
0.15 y = 0.004x + 0.080
y = 0.005x + 0.079
R² = 0.128
0.1 R² = 0.300 0.1
0.05
0
0
Harvest1 Harvest2 Harvest 3 Harvest 4
Harvest1 Harvest 2 Harvest 3 Harvest 4
0.45
Graph for early recovering genotypes
0.6
0.4 Pigments for susceptible
y = 0.025x + 0.313
0.35 R² = 0.868 0.5 y = -0.014x + 0.446
R² = 0.045
0.3
0.4
y = 0.045x + 0.072
0.25 R² = 0.977
Chla
0.3
0.2 y = 0.007x + 0.169 Chlb
R² = 0.029 cart
0.15 y = 0.015x + 0.042 0.2
R² = 0.961 y = 0.000x + 0.084
0.1 R² = 0.000
0.1
0.05
0
0
Harvest1 Harvest2 Harvest 3 Harvest 4
Harvest1 Harvest2 Harvest 3 Harvest 4

Changes in carbohydrate Profiles
0.4 Total carbohydrate metabolite changes 0.45 Carbohydrate profiles for Stay green
0.35 0.4
y = 0.039x + 0.174
y = 0.009x + 0.251
R² = 0.432 0.35
0.3 R² = 0.015
0.25 0.3
y = 0.012x + 0.156
R² = 0.308 0.25
0.2
0.2 y = 0.023x + 0.138
0.15 y = -0.017x + 0.15
R² = 0.377
R² = 0.6
0.15
0.1
0.1 y = -0.023x + 0.164
0.05 R² = 0.743
0.05
0
Harvest 1 Harvest 2 Harvest 3 Harvest 4 0
Harvest 1 Harvest 2 Harvest 3 Harvest 4
0.3 Carbohydrate profile for Early recovering
0.5 Carbohydrate profiles for susceptible varieties
0.25 0.45
y = -0.006x + 0.216
R² = 0.067 0.4
0.2 y = -0.005x + 0.278
0.35 R² = 0.002
0.15 0.3
Free RS
y = -0.011x + 0.197
R² = 0.474 0.25 Bound RS
0.1 0.2 Starch
y = -0.013x + 0.126 y = 0.015x + 0.162 Content
R² = 0.634 R² = 0.291
0.15
0.05
0.1 y = -0.016x + 0.137
R² = 0.502
0 0.05
Harvest 1 Harvest 2 Harvest 3 Harvest 4 0
Harvest 1 Harvest 2 Harvest 3 Harvest 4

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
Stay green
varieties
NASE 2 MH97/0067 0686
Early recovering
varieties
266 BAM 72-TME 14
Typical susceptible
variety NASE 1