Cassava Morphological Characteristics Importance of Cassava cassava breeding approach importance of cassava trait evaluation at different breeding stages

1. Cassava Morphological
Characteristics and trait
evaluation at different breeding
stages
2015 AGRA Training Workshop for
Research Technicians in Breeding
Kulakow/Parkes/Aina
Cassava Breeding Unit, IITA

2. OUTLINE
• Importance of Cassava
• Cassava biology and taxonomy
• Production statistics
• cassava breeding approach
• cassava agronomical considerations
• Growth morphology
• Morphological characterization of cassava
• Class activity
• Format for different trial stages
• Data collection at different trial stages
• Selection index
• Take home tips

4. Importance of Cassava
• Cassava originates from Latin America and was introduced
into Africa over 400 years ago
• feeds more than 500 million people in Africa, Asia, and Latin
America (Roa et al., 1997)
• is an important food security crop in Africa and is fast
becoming a commercial crop
• Now recognized as a suitable commodity to drive Africa’s
economic development
• Used in various food forms, animal feed and industrial raw
material (starch, ethanol, adhesives etc),

5. Biology and taxonomy of Cassava
• perennial shrub that grows erect to heights between 1-4m
• propagated vegetatively using cuttings and through botanical
seeds for breeding activity
• shoot system: stem, leaves and reproductive inflorescence
• root system: fibrous or feeder roots and tuberous roots
class - Dicotyledoneae
family- Euphorbiaceae, (7,200 species)
genus - Manihot
species- M. esculenta (cultivated form),
M. flabellifolia and M. peruviana. (wild form)
family- Euphorbiaceae: Hevea brasilensis latex, while others
produce oil (Ricinus communis

6. Leaf and inflorescence
• palmate leaves bearing 3 to 9 lobes and covered with a shiny,
waxy epidermis.
• Cassava is monoecious, bearing separate female and male
flowers on the same plant, flowers are borne together in the
inflorescences, with the pistillate flowers beneath the
staminate with female flowers opening one to two weeks
before the male flowers on the same inflorescence
• The female flowers open for approximately one day, and the
stigma is receptive throughout that time

7. inflorescence
• Flowering may also be influenced by environmental factors
with some clones not flowering in some locations, flowering
in others while some do not flower at all
• Female flowers have 5 sepals, which can be red, yellow, or
purple, and a sticky stigma which secretes nectar on the day
the flower opens
• each male flowers has 10 stamens, borne in two rings and
smaller in size compared to female flowers, approximately 5
mm, but more numerous

8. more about cassava
• Cassava is grown on a variety of soils, and it tolerates marginal, low-fertility,
acid soils better than many other staple crops
• Cassava responds favourably to added fertilizer, especially k, but over-
fertilization, especially with nitrogen, can increase leaf growth at the
expense of root formation
• removes less nitrogen and phosphorous per tonne of dry matter (DM)
produced than other common crops
• Competition with weeds, PPD , flowering challenges and biotic constraints
are considered major limitation to cassava
• Disease control is mostly accomplished through the use of resistant
varieties, selecting planting materials from disease free plant and early
removal of diseased plants

9. Area under cultivation
Area Cultivated 2010 2011 2012 2013 %
(million ha)
World 19.5 20.5 20.8 20.7
Africa 13.0 13.8 10.0 14.2 68.4
Nigeria 3.5 3.7 3.9 3.9 18.6
DRC 1.9 2.2 2.2 2.2 10.6
Ghana 0.9 0.9 0.9 0.9 4.2
Angola 0.9 1.1 1.1 1.2 5.6
Mozambique 1.2 1.2 0.8 0.8 3.8
Tanzania 0.9 0.7 1.0 1.0 4.6
Uganda 0.4 0.4 0.4 0.4 2.1
Asia 3.9 4.1 4.2 4.2 20.2
Thailand 1.2 1.1 1.4 1.4 6.7
Indonesia 1.2 1.2 1.1 1.1 5.2
Vietnam 0.5 0.6 0.6 0.5 2.6
India 0.2 0.2 0.2 0.2 1.0
Latin America 2.4 2.3 2.3 2.1 10.3
Brazil 1.8 1.7 1.7 1.5 7.3
Colombia 0.2 0.2 0.2 0.2 1.1
Paraguay 0.2 0.2 0.2 0.2 0.9
Source: FAO,2014

10. Cassava Production (MMT)
Cassava Production 2010 2011 2012 2013 %
(million Mt)
World 243.05 261.76 269.12 276.72
Africa 134.4 147.41 149.4 157.98 57.1
Nigeria 42.53 52.4 54 54 19.5
DRC 15.01 15.02 16 16.5 6.0
Ghana 13.5 14.25 14.54 14.55 5.3
Angola 13.85 14.33 10.63 16.41 5.9
Mozambique 9.73 10.09 10.05 10 3.6
Tanzania 4.54 4.64 5.46 5.4 2.0
Uganda 5.28 4.75 4.92 5.22 1.9
Asia 74.95 80.47 88.97 88.22 31.9
Thailand 22 21.91 29.84 29.3 10.6
Indonesia 23.91 24 24.17 23.93 8.6
Vietnam 8.59 9.89 9.74 9.74 3.5
India 8.05 8.07 8.74 7.23 2.6
Latin America 31.94 32.09 29.19 28.77 10.4
Brazil 24.96 25.34 23.04 21.22 7.7
Paraguay 2.62 2.45 1.68 2.8 1.0
Colombia 2.08 2.13 2.25 2.48 0.9
Source: FAO,2014

11. Cassava Yield (t/ha)
Cassava Average Yield 2010 2011 2012 2013 %
(t/ha)
World 12.4 12.8 12.9 13.3
Africa 10.3 10.7 10.7 11.1 -16.5
Nigeria 12.2 14.0 14.0 14.0 5.2
DRC 8.1 6.9 7.3 7.5 -43.8
Ghana 15.4 16.0 16.7 16.7 25.3
Angola 15.6 13.4 10.0 14.1 5.3
Mozambique 7.8 7.8 13.2 12.8 -3.9
Tanzania 5.2 6.3 5.7 5.7 -57.4
Uganda 12.7 11.2 11.5 12.0 -9.9
Asia 19.3 19.7 21.0 21.1 58.1
Thailand 18.8 19.3 21.9 21.8 63.6
Indonesia 20.2 20.3 21.4 22.5 68.4
Vietnam 17.3 17.7 17.7 17.9 34.1
India 34.8 36.5 38.6 35.0 162.0
Latin America 12.9 13.0 12.9 12.9 -3.1
Brazil 13.9 14.6 13.6 13.9 4.3
Paraguay 14.8 13.5 9.8 16.0 19.9
Colombia 10.6 10.5 10.7 10.7 -19.7
Source: FAO,2014

12. Cassava Breeding Approach
1. Identify desirable parents – from available germplasm
collection and also from partners
IITA - over 2700 accessions of locally selected cultivars
CIAT- nearly 6000 accessions
2. Generate variation: Hybridization technique (controlled
crosses) Desirable parents selected for hybridization
3. Selection for desired trait characteristics meeting
specific end users objective: progenies with favourable
alleles selected at the seedling nursery and advanced
through various breeding stages CET, PYT, AYT, and UYT

13. Hybridization in cassava
Female and Male flower Bagging and pollination
Fruit Seedling nursery
seed
Clonal evaluation

14. Typical Cassava Breeding Cycle
Seedling nursery (SN)
(no replication)
Multi-location
Uniform yield trial (UYT)
(4 replications)
Clonal evaluation (CE)
(no replication)
Preliminary yield trial (PYT)
(2 replications)
Advanced yield trial (AYT)
(4 replications)
Crossing Blocks
–
Source
Populations
National Variety
Testing and
On-Farm Trials
Year 1
Year 2
Year 3
Year 4
Years 5 & 6
Multiplication
and Release
NARS/
PARTNERS
Years 7 & 8
RapidMultiplication
One-cycle of
recombination
in 8 years.
Potential to
shortened
breeding cycle
using genomic
selection

15. Summary of cassava varieties
Released in Nigeria (1976-2014)
S/No Year of release No. of
genotypes
released
1 1976 1
2 1984 1
11 1986 15
12 1988 1
13 2005 6
14 2006 5
15 2009 2
13 2010 4
14 2011 5
15 2012 3
16 2014 3
Total 46

16. agronomical considerations
• Age and length of planting materials
• Stem cutting
• Stem storage
• Timely planting
• Spacing and plant population
• Supply of missing plants
• Fertilizer application the ‘4Rs’
• Weed control
• Rouging of off-types
• Disease and pest control
• Field evaluation and data collection
• Laboratory analysis
• Reporting

17. land preparation and weed control in cassava field

18. Growth morphology
• Sprouting stage (5-15 DAP): First adventitious roots from the buds under
the soil within 1 week of planting (5-7 DAP), small leaves emergence at 10-
12 DAP and full leaf emergence achieved at 15 DAP
• Leaf development and root system formation stage (15-90 DAP): leaves
expansion with the initiation of photosynthetic process (30 DAP), growth of
fibrous roots begins to replace adventitious roots and actively functioning
in water and nutrient adsorption. Few fibrous becomes storage roots (60 to
90 DAP).
• Stems and leaves (canopy) establishment stage(90-180 DAP): leaves
intercept most of the incident light on canopy with maximum growth rates
of leaves and stems achieved with DM partitioned to leaves and stems, as
storage root continues to bulk.

19. growth morphology cont’d
• Assimilate translocation to roots stage (180-300 DAP):
Storage root bulking enhanced as assimilate is partitioned
from leaves to roots with the highest rate of DM
accumulation in storage roots
• Dormancy stage (300-360 DAP): Leaf production rate
decreased, leaf fall increases as shoot vegetative growth is
terminated. Translocation of starch to root is maintained.
Plant completes 12 month cycle, to be followed by a new
period of vegetative growth when moisture becomes
available

20. Cassava Morphological Descriptor
14: Root neck length:

21. Why characterization
• to determine the genetic diversity among cassava genotypes
• prerequisite for genetic improvement through the extent of
genetic variation present between cultivars
• Enables the selection of diverse parental combinations and
broaden genetic base of a breeding population
• high levels of diversity suggest a recombination and gene flow
which can play an important role in the preservation of
species diversity

22. Unexpanded leaf, petiole and stem color
98/0581
Dark brown silver green Silver green
Green purple; green green purple; green purple; red

23. Cassava Plant type
Umbrella Compact open

24. s/n Trait Time
schedule
Phenotypic class and
Score
1 unexpanded leaf color 1-3MAP 3= light green
5= dark green
7= purplish green
9= purple
2 1st
fully expanded leaf color 1-3MAP light green
green purple
purple
3 pubescence of young leaves 1-3MAP 0=absence
1=presence
4 flowering 3-6MAP 0= absence
1 =presence
5 anthocyanin distribution on
petiole
6MAP absent
top to bottom
totally pigmented
6 growth habit of stem 9MAP 1= straight,
2= zigzag
7 stem color 9MAP 1= Silver green
2= light brown/orange
3= dark brown
8 Plant type 12 MAP 4= compact
3= Open
2= Umbrella
1= Cylindrical

25. s/n Trait Time
schedule
Phenotypic class and
score
9 central leaf lobe shape 1-3MAP 1= ovoid
2= elliptic lanceolate
3= obovate lanceolate
4= oblong lanceolate
5= lanceolate
6= straight or linear
7= pandurate
8= linear pyramidal
9= linear pandurate
10= linear
hostatilobalate
10 petiole color 3-5MAP 1= yellowish green
2= green
3= reddish green
5= greenish red
7= red
9= purple

26. Evaluation for yield parameters at harvest
s/n Trait Mode of
evaluation
Remark/score
1 Number Harvested count reflect sprouting ability
2 Root number count suggest tuberization potential
3 Root Weight (Kg) weighing Low/medium/high fresh yld
4 Shoot Weight (Kg) weighing Useful in estimation of HI
5 Root Size visual small, medium, or large sized roots
3 = small, 5 = medium, 7 = large
Marketable and unmarketable root
distribution
6 Root Shape visual 1 = Conical, 2 = Conical-cylindrical
3 = Cylindrical, 4 = Fusiform
5 = Irregular, 6 = Combination

27. Schedule for scoring of vigor, sprout and diseases
Parameter Schedule Scoring scale
Sprout 1MAP Count
Vigor 1MAP 3, 5 & 7
CMD1 1MAP 1, 2,3,4 & 5
CMD3 3MAP 1, 2,3,4 & 5
CMD6 6MAP 1, 2,3,4 & 5
CBB3 3MAP 1, 2,3,4 & 5
CBB6 6MAP 1, 2,3,4 & 5
CGM1 & CGM2 6-9MAP 1, 2,3,4 & 5
CAD 9 9MAP 1, 2,3,4 & 5
Stay green 6-9MAP 1,3,5,7,9

28. Selection of parents for hybridization
S/N Trait Var1 Var 2 Var 3 Var 4
1 Stem color light green dark green purple
green,
brown
2 Petiole color Light green dark green purple red
3 Plant type compact open umbrella cylindrical
4 Stem growth
habit
upright upright Zig-zag upright
5 CMD resistance susceptible tolerant resistant tolerant
6 CBB resistance susceptible tolerant resistant susceptible
7 DM content high moderate low moderate
8 Fyld low moderate moderate low
9 Flowering ability present present present present
10 HCN potential high moderate low moderate
11 Poundability mealy Slightly mealy Non-mealy mealy
12 Pubescence little moderate high moderate
13 Root color white white yellow white
Class activity: Identify 5 specific breeding objectives and select potential
parents for possible hybridization activities

29. Format for different trial stages
S/N Trial rep loc Plot size spacing Design
1. SN nil single 20m block 1m x 0.25m
2 CET nil single 6X1 1m x 0.8m Augmented
3 PYT 2 1-2 7x2 1m x 0.8m RCBD
4 AYT 4 2-3 7x4 1m x 0.8m RCBD
5 UYT 4 4 7x6 1m x 0.8m RCBD
6 NCRP 4 8-10 6x6 1mx1m RCBD

30. Parameters evaluated at different trial stages
- Seedling Nursery
- Root number
- Dry matter on selected plants
- Plant type
- Mealiness on selected plant
- Yield (visual) high/low
- DM by mouth or feel
- Diseases score
- Total Carotene Chart
- Clonal evaluation
- yield trials (PYT, AYT, UYT)
- Sprout count and vigour at 1MAP
- Disease evaluation at 1MAP: CMD
- Diseases 3MAP: CMD, CBB
- Diseases 6MAP: CMD, CBB, CAD,
- Diseases 9 MAP: CAD, CGM
- Visual rating 6MAP
- Pre- harvest (1 week before harvest)
- Harvest at 12MAP
yield and yield related parameters)

31. Final genotype selection
• Use appropriate selection index to rank and select
desirable genotypes
• CBU, IITA uses selection index that incorporates the
following to generate index rank
- DYLD = 60%
- CMD =25%
- HI = 15%
This index rank is then compared with the pre-
harvest visual rating

32. Description Evaluation
time
Scoring scale and Description
Plant type 12MAP 1= Cylindrical, 2= Umbrella,
3= Open, 4= compact
Lodging 12MAP 1= about 90% of plant are erect with no sign of root
exposure
2=50% of plants not standing upright
3= 80% 0f the plant bent with roots exposed
Branching 12MAP 1= No branching at all
2= branching height above 1.5m
3= branching height at 1m to 1.5m
4= branching height at 0.5m - 1.0m
5= branching height at 0.5m

33. visual
rating
12MAP 1= excellent plant architecture, no sign of lodging and is CMD
free
2= very good architecture, CMD free, no lodging and good
vigour
3= desirable plant architecture, no visible sign of CMD, no
lodge and good vigour
4= undesirable plant architecture, moderate vigour,
moderate disease severity and moderate level of lodge
5= poor vigour, undesirable plant architecture,

34. Take home tips
• Be vigilant on the field
• Have the eye of a breeder
• Understand trial objective/s
• Ask qusetions when/if necessary
• Follow established protocol of activity
• Proper field labelling
• Do a check list before embarking on field activity
• Learn from previous mistakes and avoid such in future
• enhance your intellectual capability and capacity
• quality data capture helps to enhanced research
DSC_0505.AVI

35. Thanks for listening