GENETIC ENHANCEMENT OF BETA-CAROTENE IN STORAGE ROOTS OF CASSAVA VARIETIES IN AFRICA

International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org

GENETIC ENHANCEMENT OF BETA-CAROTENE IN

STORAGE ROOTS OF CASSAVA VARIETIES IN AFRICA:

WHERE DO WE STAND?

A.G.O. Dixon, G.N. Ssemakula, B. Maziya-Dixon

and J.M. Ngeve

International Institute of Tropical Agriculture, PMB 5320 Ibadan, Nigeria.


Outline Of Presentation

Screening cassava germplasm for β-carotene

Evaluation of β-carotene-rich genotypes: agronomic

characteristics

Introduction of germplasm from within and outside SSA

Gene introgression for the improvement of β-carotene levels

Deployment of β-carotene-rich germplasm to NARS in SSA

Assessment of effect of processing on β-carotene retention in

cassava foods and profiling of cassava carotenoids.

Participatory on-farm trials and variety release

Opportunities and challenges and the way Forward


The Cassava Germplasm Development-

Africa Component of H+

Initiated at IITA in 2003

Global objective

Develop cassava varieties with high ß-carotene,

levels in the roots packaged in preferred

agronomic backgrounds, and make these

varieties available to farmers in SSA


Strategic objectives

- Increase micro-nutrient (pVAC, Fe, Zn) content in cassava

- Increase protein content in cassava

- Reduce hydrocyanic acid content in cassava


Tactical objectives

- Characterize cassava products for pVAC, Fe and Zn

- Characterize cassava products for protein quality

and quantity

- Characterize cassava products for levels of HCN

- Develop source populations for selection for these

traits


Screening traits of interest in

cassava germplasm

Development of sampling method: which portion of

the root? What maturity?

Longitudinal, distal, central, and proximal portions of

cassava roots

Sampling at 6, 9, and 12 MAP

Correlation between values from different portions


β-carotene 6 & 9 MAP df =24 T value = -7.96 p <.0001

β-carotene 6 & 12 MAP df =24 T value = -7.34 p <.0001

β-carotene 9 & 12 MAP df =24 T value = 2.53 p = .0182

Sampling at 12 MAP adopted

Visual rating for carotenoid concentration vs actual concentration

Mean micronutrient

concentrations 6, 9, &12 MAP

β-carotene (μg/g) Fresh root weight

MAP 6 9 12

Mean 0.33 3.08 2.09

SE 0.25 0.88 0.65


Year Total

No.

families

Total

No.

plants

Screening method Deep

yellow

selected

Light

yellow

selected

Min

TC

Max

TC

2004/05 476 16,832 Color chart 24 379 - 10.1

μg/g †

2005/06 982* 19,644 Color chart,

spectrophotometric

895 1386 2.8

μg/g

11.9

μg/g

2006/07 490 8743 Color chart,

spectrophotometric

667 158 1.23

μg/g

14.81

μg/g

2007/08 638 28,865 Color chart,

spectrophotometric

1548 >500 1.56 13.27

* Comprised of 133 families from CIAT, 59 from Brazil, and 790 local crosses from IITA Ibadan ;

†Obtained from 2005 clonal evaluation; Screening done at different stages of the breeding prog.

Carotenoids (fresh wt basis)

from screening cassava in 4 yrs


Selection stage

2009/10

Range of pVAC in

storage roots

Clonal Evaluations 0.2 – 10.4

Advanced Yield Trials 4.7 – 11.1

Uniform Yield Trials (UYT) 0.58 – 9.5

Levels of pVAC in different stages of selection in 2009


Levels of pVAC in genotypes advanced from

seedling nursery to clonal evaluation in 2009


Levels of pVAC in genotypes selected and

evaluated in advanced/UYT trials in 2009


G x E: carotenoid concentration FW basis)

AMMI:

High G –TC

G x E – highly

sig for TC

Carotenoid

concentration is

a stable trait

Single location

selection reliable


Resistance to pests &

diseases

Stem yield & architecture

Root number &

size/weight

Root quality

Stability - across locations

Seedling nursery

Clonal Evaluation

Preliminary Trial

Advanced Yield Trial

Uniform Yield Trials

OFAR Trials

Agronomic superiority for

acceptability


05/1601 1.0 2.0 36.5 38.9 9.4

05/1600 3.2 2.5 34.5 29.0 6.5

05/1570 1.0 2.0 33.3 41.9 2.4

05/0327 1.0 4.5 28.4 37.8 6.2

05/1862 1.2 2.5 27.1 39.3 4.5

05/0311 1.0 2.5 25.7 40.9 5.5

05/0099 1.0 2.0 25.1 38.9 5.8

05/1654 1.0 3.0 23.0 34.9 6.9

05/0476 1.0 3.0 19.7 40.3 4.0

05/1652 1.0 2.5 19.5 31.3 8.3

Agronomic characteristics and pest reactions

of promising micronutrient-rich clones

Clone CMD CGM Yield DM Carotene

(t/ha) (%) (µg/g)


G x E : fresh root yield

E effect highest for yield

G x E*** for yield


G x E : DM content

G effect highest for DM

G x E*** for DM


Source Form Quantity

Tanzania Landarace 18

Malawi Landarace 14

Zambia Landarace 11

Latin America ,

Thailand

Landarace ,

improved clones

44

CIAT Seed populations 207 families

(4754 seeds)

Brazil (thru CIAT) Seed populations 59 families

(8074 seeds)

Acquisition of β-carotene-rich and

African adapted germplasm


Introgression of genes to enhance carotene

levels in IITA germplasm

Season Families Seeds

2003/04 499 >16000

2004/05 790 19,644

2005/06 490 14,000

2006/07 859 33,548

2007/08 725 54,295

2008/09 166 9006

Total 3529 146,493


Virus-free certified tissue culture plantlets

Deployment of germplasm

Country Seed families No. of seeds

Guinea 71 >10,100

Congo DR 30 >10,000

Uganda 64 >10,100

Kenya 23 >23,000

Malawi 24 >24,000

Angola 23 >23,000

Mozambique 23 >23,000

Sierra Leone 23 >46,000

Ghana 17 >18,100

HS seed families


Colchicine induced

polyploidy >20 YR Clones

4x versus 2x counterparts

Effect of polyploidization on

carotene content

(carotene 4x>carotene2x)

Tetraploid x diploid crosses

for more productive triploids

Polyploid breeding for enhanced

carotene content


• Tetraploids had significantly higher concentrations of total carotene than diploids

• Mean dry matter content of tetraploids was significantly lower than of diploids

• Clone X ploidy level interaction was significant

• Some tetraploid clones had higher dry matter content over the mean

Comparative analysis for total carotene and dry matter

content of 20 artificially induced Tetraploids (4x)

vs their diploid counterparts (2x)

TC DM %

Parameter 2X 4X Mean 2X 4X Mean

Mean 4.7 5.4 5.03 36.78 33 35.5

SE 0.6 0.7 0.59 0.9 0.7 0.75

Min 0.4 0.7 0.57 27.19 28 29.67

Max 8.4 10 9.18 42.49 38 42.44

Pr>F (Ploidy level) *** ***

Pr>F (Clone) *** ***

Pr>F (Clone*Ploidy level) *** ***


Mutation breeding – (with IAEA)

TMS lines 01/1371, 98/0002 irradiated with gamma rays

Mutants cloned and total carotene (TC) determined

Worth of mutation breeding in enhancing nutrient concentration

Effect of irradiation with gamma rays/fast neutron on β-carotene

concentration

30, 600 seeds irradiated (100 families), nursery ~ 2, 797 seedlings harvested,

cloned and selfed

Parameter TC

Mean 6.09

SE 0.12

Min 3.55

Max 9.74

N 112


Crop Pot Plate Mouth Intestine

Nutrient loss during processing: an

inevitable and unfortunate reality


0

10

20

30

40

50

60

70

80

90

100

Boil Raw fufu Cooked fufu Gari chips

Processed product

% n

utri

ent r

eten

tion

Total carotene

β-carotene

Iron

Zinc

Highest nutrient retention in boiled roots

True micronutrient retention (%) of cassava products prepared from

fresh storage roots of three elite yellow-fleshed cassava clones


True micronutrient retention (%) of gari prepared

from 24 elite yellow-fleshed cassava clones

Micronutrient retention is genotype dependent

Genetic variation for micronutrient retention can be exploited via breeding

0

5

10

15

20

25

30

35

40

45

50

01/111

5

01/122

4

01/123

5

01/127

3

01/127

7

01/133

1

01/133

5

01/136

8

01/137

1

01/141

2

01/141

3

01/144

2

01/161

0

01/164

6

01/164

9

01/166

2

01/166

3

90/015

54

94/000

6

94/033

0

95/037

9

98/213

2

Total carotenoids in fresh roots (µg/g)

Total carotenoids in Gari (µg/g)

% True total carotenoids retention*


Carotenoids profile of 22 yellow-fleshed cassava genotypes

90% of carotenoids in cassava is β-carotene

> 50% of carotenoids in cassava is Trans- β-

carotene


Carotenoids species in yellow-fleshed cassava

clones evaluated at 5 locations in Nigeria, 2005/06


Shift in nutrient levels with conventional

breeding and selection for nutritional quality

Micro-nutrient Baseline 2003/2004 2004/2005 2005/2006 2006/2007 2007/2008 2008/2009

Total carotene 0.4 μg/g 4.8 μg/g 10.1μg/g 11.9 μg/g 14.8μg/g 13.3 μg/g 10.4 μg/g


Participatory on-farm evaluation and

release of yellow-fleshed cassava

Objectives

Assess performance of yellow-fleshed clones under

farmer managed conditions

pluses (+) and minuses (-) of the clones – farmers’

perspective

Farmer exposure to yellow genotypes

SE states: Abia, Imo, Anambra, Enugu, Ebonyi, Akwa

Ibom,& Cross River

SW states: Lagos, Ogun, Ondo, Ekiti, Oshun, & Oyo

Preferences

96/1089A, 01/1115, 01/1371, 01/1412,

01/1368, 98/2132, 30572, 01/1663,

01/1610, 01/1235, 01/1404

Selection criteria

Yield, processed product yield and

quality, tuber size, no need to fortify

gari with palm oil, color, recognition

Skeptical farmers- yellow cassava a

GMO?!Farmer carries a tuber of 01/1404; it

weighed more than 6 kg


98/2132 5.9 5.3 5.1 4.7 5.901/1368 5.4 5.2 5.0 4.8 5.794/0006 4.2 4.4 4.0 3.8 5.195/0379 4.7 4.6 4.0 4.6 5.096/1089A 4.3 4.8 4.3 4.7 4.901/1380 4.9 4.8 4.6 4.3 4.890/01554 4.5 4.4 4.1 4.3 4.801/1277 4.9 4.1 3.9 3.0 4.401/1649 4.7 3.9 3.9 3.7 4.401/1663 4.1 3.8 3.9 4.0 4.4

TME 1 1.3 2.1 2.6 2.0 1.630572 4.2 4.1 3.6 3.8 4.691/02324 5.3 5.2 4.7 4.7 5.7

Clone Color Texture Mealiness Starchiness Overall

acceptability

Scored on a

1-6 scale

where:

1=poor

6= very

good

Levels of acceptability of food from yellow

root cassava: Gari


1. Correlation of Total Carotene (TC) to Fresh root Yield

(FYLD) and dry mater content (DM) was negative and

significant for some trials.

2. Across all yellow root trials , the correlation remained

negative but was not significant

Trait Association


Status of germplasm introduced to target

NARS (Nigeria and DR Congo)

Nigeria• Improved seed populations have been planted in seedling nurseries

• Improved genotypes with high pVAC are in various selection trials

• Three high pVAC genotypes are in pre-release trials

DR Congo• Improved seed populations have been planted in seedling nurseries

• Improved genotypes with high pVAC are in various selection trials

• Germplasm collection of high pVAC genotypes is maintained at

Mvuazi

• Hybridization of high pVAC parents is ongoing

• Product and market development and sensitization key to

release of new pVAC varieties before 2012.


Nigeria: TMS 96/1089A - First ever Official release of

yellow-flesh cassava variety

DR Congo: TMS 94/0330 and TMS 01/1661

Official Releases in Africa

Yellow cassava in Nigeria (Gari) and DR Congo (fufu, chikwangue,

fresh roots) have higher price premium than white or cream ones

Yellow Gari

White Gari


Variety

Fresh

Yield

(t/ha)

Dry

matter

(%)

Starch

content

(%)

CMD CBSD Color

Total

carotene

content

(μg/g) FW

94/0330 27.8 40.5 21.5 1.3 1.0 Yellow 5.23

01/1661 39.6 28.8 14.0 1.0 1.0 Yellow 7.29

TME

41945.6 39.3 28.9 1.0 1.0 White

-

RAV

(check)14.0 31.3 20.3 3.0 1.0 White

-

Characteristics of YR varieties released in

DR Congo by INERA in June 2008.


Opportunities and challenges

Opportunities

High prospects of hitting the target level (15 μg/g) for

β-carotene

Some countries (Nigeria, DR Congo and Ghana) are

already exposed to and/or using yellow root cassava -

attitude may not be a major issue


Some of the high carotenoid clones are weak, probably

because they resulted from selfing

Often high carotenoid clones have low DM and low yield

Plateauing of Total Carotene

Will have to develop early bulking varieties since carotene

is lost with age in the ground, ie > 9 months

Challenges

Opportunities and challenges;

lessons learnt


Way forward

• Introduce diverse genotypes with higher levels of beta carotene (esp. mealy deep yellow/orange parents)

• Identify parents with high breeding values for deep yellow-fleshed roots, mealiness, high dry matter content, low CnPand resistance to CMD and CBSD for use in crossing blocks

• Develop source population for yellow-fleshed roots by crossing selected genotypes to locally adapted lines

• Multiply and distribute available beta-carotene and agronomically superior genotypes for selection under local environmental conditions

• Sensitize the population on the importance of consuming beta-carotene rich cassava varieties


• Investigating the underlying environmental and agronomic factors on pVAC trait expression

• Use of index selection for overcoming the negative association between pVAC and yield/DM


Acknowledgements:

HarvestPlus and IITA, NRCRI and INERA

Thank You!

GENETIC ENHANCEMENT OF BETA-CAROTENE IN STORAGE ROOTS OF CASSAVA VARIETIES IN AFRICA

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