Genotypic variation in fresh root colour, harvest period and
dry matter content of improved cassava genotypes
Njoku, D.N; Egesi, C.N; Vernon, G; Offei, S.K; Asante, I and Kulakow, P
Introduction
 White cassava varieties are low in beta-carotene but high in dry matter
content.
 Newly introduced yellow cassava varieties high in beta-carotene are
usually very low in dry matter content and this may affect adoption.
 development of higher B-carotene cassava in Nigeria will contribute to:
• 1. a sustainable solution of vitamin A deficiency already identified
among regular cassava consumers in Nigeria.
• 2. market potential of cassava as food and feed can be enhanced.
• 3. other by-products or value -added products of cassava such as chips,
starch, gari, bio-fuel and bio-fertilizer can provide employment
opportunity and economic empowerment to agricultural sub-sector in
Nigeria.
Objectives
This study was undertaken to screen some selected
genotypes in NRCRI cassava germplasm with a
view to:
• determine total carotene content
• dry matter content
• compare the spectrophotometric and standard
colour chart methods of total carotene content
determination available at NRCRI
Materials and Methods
8 cassava genotypes were planted at NRCRI Umudike in 2008. 5 genotypes have
yellow fleshed root while 3 were white fleshed root.
Harvesting were carried out at 11 and 13 MAP. Samples were prepared for analysis
according to Harvest-Plus procedure.
Visual observation using colour and total carotene content were determined
spectrophotometrically, using the formula:
TCC (μg/g) =
A x volume (ml) x 104
———————–
A1%1cm x fresh sample weight (g)
where A= absorbance; volume = total volume of extract
A 1%1cm = absorption coefficient of β-carotene in PE (2592).
The dry matter was done by oven drying about 30g of the sample at 700C until no
moisture remains and a constant weight was obtained.
%DMC =
dry weight of sample x 100.
fresh weight
Results and Discussion
8
7
TC ug/g
6
5
4
TC 11 MAP
3
TC 13 MAP
2
1
0
Genotypes
45
40
35
DMC (%)
30
25
20
DMC 11
15
DMC 13
10
5
0
Genotype
Fig 1: dry matter content of cassava genotypes at different harvesting periods
7
8
6
7
6
5
13 MAP
3
11 MAP
2
TC ug/g
Color chart
5
4
4
TC 11 MAP
3
TC 13 MAP
2
1
1
0
0
genotypes
Genotypes
9
8
y = -0.1176x + 7.467
R² = 0.2357
7
TC (ug/g)
6
5
4
3
2
1
0
0
5
10
15
20
25
30
DMC (%)
Fig 2: Relationship of total carotene with dry matter content
35
40
45
50
y = 2.6674x - 1.2034
R² = 0.2177
6
5
TC ug/g
4
3
2
1
0
0
0.5
1
1.5
CMD
Fig 3: Relationship of total carotene with CMD
2
2.5
Conclusion
Carotene content of cassava roots screened with
available standard colour chart and
Spectrophotometer readings were positively correlated
and also high.
This demonstrate the potential of yellow roots cassava
as contributing in overcoming vitamin A deficiency
(VAD) found especially among daily consumers of
cassava in Nigeria.
Although delay harvesting may lead to an increase in
carotenoid content, but it negatively affects dry matter
content which may also affect adoption by farmers. So,
there is need to overcome this challenge by breeders.
Acknowledgement
Mrs. Njoku, Sylver
Dr. Eke-okoro, ON
Dr. Ceballos, H
Mr. Alamu
Dr. Akinbo, O
Dr. Bunmi, O
Onwuka Samual
Ivory Chimaobi
Dr. T.O. Ezulike
References: Chavez et al, 2008; Esuma et al, 2012
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