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

80

160

240

320

40

60

80

100

300

600

900

00 5 10 15 20 2525

Time mins

Vis

cosi

ty R

VU

Tem

p 'C

Sp

eed

RP

M

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

-150

-100

-50

0

50

100

150

200

250

300

350

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

0

0.1

0.2

0.3

0.4

0.5

RS1(Wk1) RS2(WK3) RS3(WK5) RS4(WK7

A

y = -0.0718x + 0.6025

R² = 0.1433

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

RS1(Wk1) RS2(WK3) RS3(WK5) RS4(WK7

B

y = 0.1104x + 0.2565

R² = 0.9271

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

RS1(Wk1) RS2(WK3) RS3(WK5) RS4(WK7

C y = -0.005x + 0.407R² = 0.016

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0.45

0.5

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

0.8

1

1.2

1.4

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

0

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

0

0.2

0.4

0.6

0.8

1

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

0

0.2

0.4

0.6

0.8

1

1.2

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

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0.45

0.5

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

0

0.1

0.2

0.3

0.4

0.5

0.6

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

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

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

0

0.1

0.2

0.3

0.4

0.5

0.6

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

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

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

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0.45

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

0

0.05

0.1

0.15

0.2

0.25

0.3

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

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0.45

0.5

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