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

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

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


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

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

Carotenoids (fresh wt basis)
from screening cassava in 4 yrs

Year Total Total Screening method Deep Light Min Max
No. No. yellow yellow TC TC
families plants selected selected
2004/05 476 16,832 Color chart 24 379 - 10.1
μg/g †
2005/06 982* 19,644 Color chart, 895 1386 2.8 11.9
spectrophotometric μg/g μg/g
2006/07 490 8743 Color chart, 667 158 1.23 14.81
spectrophotometric μg/g μg/g
2007/08 638 28,865 Color chart, 1548 >500 1.56 13.27
spectrophotometric

* 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.


Levels of pVAC in different stages of selection in 2009

Selection stage Range of pVAC in
2009/10 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 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


Agronomic superiority for
acceptability

 Resistance to pests &  Seedling nursery

diseases
 Clonal Evaluation
 Stem yield & architecture
 Preliminary Trial
 Root number &
size/weight  Advanced Yield Trial

 Root quality  Uniform Yield Trials

 Stability - across locations  OFAR Trials

Agronomic characteristics and pest reactions
of promising micronutrient-rich clones
Clone CMD CGM Yield DM Carotene
(t/ha) (%) (µg/g)

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

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


Acquisition of β-carotene-rich and
African adapted germplasm
Source Form Quantity
Tanzania Landarace 18
Malawi Landarace 14
Zambia Landarace 11
Latin America , Landarace , 44
Thailand improved clones
CIAT Seed populations 207 families
(4754 seeds)
Brazil (thru CIAT) Seed populations 59 families
(8074 seeds)

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

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
Virus-free certified tissue culture plantlets
HS seed families

Polyploid breeding for enhanced
carotene content
 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

Comparative analysis for total carotene and dry matter
content of 20 artificially induced Tetraploids (4x)
vs their diploid counterparts (2x)

TC DM %
Parameter 2X 4XMean Mean 2X 4X
Mean 4.7 5.45.03 35.5 36.78 33
SE 0.6 0.70.59 0.75 0.9 0.7
Min 0.4 0.70.57 29.67 27.19 28
Max 8.4 10
9.18 42.44 42.49 38
Pr>F (Ploidy level) *** ***
Pr>F (Clone) *** ***
Pr>F (Clone*Ploidy level) *** ***
• 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

Mutation breeding – (with IAEA)
Worth of mutation breeding in enhancing nutrient concentration
Effect of irradiation with gamma rays/fast neutron on β-carotene
concentration
 TMS lines 01/1371, 98/0002 irradiated with gamma rays
 Mutants cloned and total carotene (TC) determined
Parameter TC
Mean 6.09
SE 0.12
Min 3.55
Max 9.74
N 112
 30, 600 seeds irradiated (100 families), nursery ~ 2, 797 seedlings harvested,
cloned and selfed

Nutrient loss during processing: an
inevitable and unfortunate reality

Crop Pot Plate Mouth Intestine


100
90 Total carotene
80 β-carotene
% nutrient retention

70 Iron
60 Zinc
50 Highest nutrient retention in boiled roots
40
30
20
10
0
Boil Raw fufu Cooked fufu Gari chips

Processed product

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
50
45 Total carotenoids in fresh roots (µg/g)
40 Total carotenoids in Gari (µg/g)
35 % True total carotenoids retention*
30
25
20
15
10
5
0
01 5

01 4

01 5
73

01 7

01 1

01 5

01 8

01 1

01 2
13

01 2

01 0

01 6

01 9

01 2
90 63

94 6

95 0

98 9
32
4
55
1

2

3

7

3

3

6

7

1

4

1

4

4

6

0

3

7
/1 1

/1 2

/1 2

/1 2

/1 2

/1 3

/1 3

/1 3

/1 3

/1 4

/1 4

/1 4

/1 6

/1 6

/1 6

/1 6

/1 6

/0 0

/0 3

/0 3

/2 1
/0 1
01

01

01

94
Micronutrient retention is genotype dependent
Genetic variation for micronutrient retention can be exploited via breeding

90% of carotenoids in cassava is β-carotene
> 50% of carotenoids in cassava is Trans- β-
carotene

Carotenoids profile of 22 yellow-fleshed cassava genotypes

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

Preferences
Objectives
 96/1089A, 01/1115, 01/1371, 01/1412,
 Assess performance of yellow-fleshed clones under
01/1368, 98/2132, 30572, 01/1663,
farmer managed conditions
01/1610, 01/1235, 01/1404
 pluses (+)
Selection criteria and minuses (-) of the clones – farmers’
 perspective
Yield, processed product yield and
 Farmer size, no need to fortify
quality, tuber exposure to yellow genotypes
gari with palm oil, color, recognition
 Skeptical farmers- yellow cassava a Enugu, Ebonyi, tuber of 01/1404; it
SE states: Abia, Imo, Anambra,
Farmer carries a
Akwa
GMO?! Ibom,& Cross River weighed more than 6 kg
SW states: Lagos, Ogun, Ondo, Ekiti, Oshun, & Oyo

Levels of acceptability of food from yellow
root cassava: Gari
Clone Color Texture Mealiness Starchiness Overall
acceptability

98/2132 5.9 5.3 5.1 4.7 5.9
01/1368 5.4 5.2 5.0 4.8 5.7 Scored on a
94/0006 4.2 4.4 4.0 3.8 5.1
1-6 scale
95/0379 4.7 4.6 4.0 4.6 5.0
where:
96/1089A 4.3 4.8 4.3 4.7 4.9
1=poor
01/1380 4.9 4.8 4.6 4.3 4.8
6= very
90/01554 4.5 4.4 4.1 4.3 4.8
good
01/1277 4.9 4.1 3.9 3.0 4.4
01/1649 4.7 3.9 3.9 3.7 4.4
01/1663 4.1 3.8 3.9 4.0 4.4

TME 1 1.3 2.1 2.6 2.0 1.6
30572 4.2 4.1 3.6 3.8 4.6
91/02324 5.3 5.2 4.7 4.7 5.7


Trait Association

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


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.

Official Releases in Africa
Nigeria: TMS 96/1089A - First ever Official release of
yellow-flesh cassava variety

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

White Gari

Yellow cassava in Nigeria (Gari) and DR Congo (fufu, chikwangue,
fresh roots) have higher price premium than white or cream ones

Characteristics of YR varieties released in
DR Congo by INERA in June 2008.
Total
Fresh Dry Starch
carotene
Variety Yield matter content CMD CBSD Color
content
(t/ha) (%) (%)
(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 -
45.6 39.3 28.9 1.0 1.0 White
419
RAV -
14.0 31.3 20.3 3.0 1.0 White
(check)


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


Opportunities and challenges;
lessons learnt
Challenges

 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


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 CnP
and 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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