This document provides information on cassava taxonomy, origin, cultivation, uses, and genetic diversity analysis using morphological and molecular markers. It discusses cassava's classification in the plant kingdom, top cassava producing countries, and its importance as a food source for over 500 million people. It also summarizes the use of phenotypic and biochemical markers, as well as molecular markers like RFLPs, SSRs, RAPDs, and AFLPs to study genetic diversity and identify cassava varieties with desired traits like cassava mosaic disease resistance.

2. Taxonomy
Kingdom : Plantae
Division : Magnoliophyta
Class : magnoliolpsida
Order : Malpighiales
Family : Euphorbiaceae
Subfamily : Crotonoideae
Tribe : Manihoteae
Genus : Manihot
Species : M. esculenta

3. Introduction
• Origin – Brazil
• Highly cross pollinated crop
• Duration – 7 months to 2 years
• Introduced to Africa and Asia from south
America
• Grown in 90 countries

4. Contd…
• Cassava ranks 4th after rice, sugarcane, and maize
• Extensively cultivated countries are Argentina,
Brazil, Colombia, and Paraguay
• Area under cultivation – 16 mha
• Provide food & livelihood for >500 million people in
the world
- Best and Henry, 1992

6. Contd…
Biochemical aspects
Root:
Roots are mostly contain carbohydrates
Also rich in vit.C, carotene, Ca, and K
Poor in protein
Leaf:
Rich in protein and vitamins
Consumed as a vegetable

7. Genome structure
• 2n = 36
• Genome size - 1.67 pg
772 M bp in the haploid genome

8. Germplasm
World germplasm collection held at CIAT, Colombia
Has around 5,724 accession
Brazil – 1,340 accessions
Colombia - 2,003 accessions
• Kenya
• Uganda
• Rwanda
• Burundi
• Congo
• Madagoscar

9. Wild species
Manihot anomala
M. caerulescence
M. epruinosa
M. flabellifolia
M. glaziovii
M. dichotoma
M. tristis
M. peruviana
M. maracasensis

10. Uses
Starch as raw material for
Paper industries
Textiles
Pharmaceuticals
Animal feed
Sago industries
and also used as a poultry feed

11. Markers
Phenotypic marker
• Graner (1942) described two morphological markers
Leaf shape
Root colour
• Hershey & ocampo (1989) described eight
morphological markers located on the stem, leaves,
and root.

12. cassava phenotypic markers
Organs Types
• Erect
Plant shape • Tall and spread
• Spread
1. Green
Colour of the 2. Yellow-green
young part of 3. Green and beginning of petiole red
the stem 4. Green and beginning of petiole red with red ribs
5. Green and red in equal area
6. Some traces of green
7. Entirely light red
• Green
Colour of the • coloured base and green scales
eye (bud) • Green base and coloured scales
• Entirely coloured

13. Emergence of eye (bud) • Deep
• Projecting
Alignment of internodes • Zigzag
(young part) • Straight
leaf shape • Palmipartite (normal shape)
• Palmisequate (the lobes totally
separate)
• Entirely green
• Yellowish green
Coloration of petiole • Vivid red
• Purple red
• Entirely purple
• Less than 3
Number of leaf lobes • 3 to 5
• 5 to 7
• 7 to 9

14. •Very narrow
•Parallel edge
Shape of lobes •Normal
•Wide
•Rounded with two widening points
•Proximal
Form of lobes defined by position of •Median
maximal widening point •Terminal
•White without chlorophyll
•Light green
Coloration of upper surface of lamina •Yellow-green
•Dark green
•Purplish
•Green
•Whitish-green
Coloration of underside of lamina •Yellow-green
•Purple of red
•Always green
•red of upperside of young leaves
Coloration of lamina nerves •red on underside of young leaves
•red on both side of young leaves

15. Leaf variation

16. Stem variation

17. Tuber variation

18. Inflorescence
1. Wide
Forms of sepals 2. Medium
3. narrow
1. Entirely green
Sepals colour in female 2. Green and coloured nerve
flower 3. Red and green
4. Red to purple
1. Always straight
Shape of 6 wings on the 2. Straight then sinous at maturity
ovary with 3 carpels 3. Sinous then straight at maturity
4. Always sinous
Ovary body colour 1. Green
2. Red

19. Root
1. Short ( < 40 cm )
Length of root 2. Normal ( 40 to 80 cm )
3. Long ( > 80 cm)
1. Conical
Shape of root 2. Fusiform
3. Cylindro-conical
4. cylindrical
1. Smooth
Texture of root surfaces 2. Medium
3. Rough
Appearance of external 1. Grey and thin
bark 2. Brown and thick
Colour of pulp 1. White
2. Yellow

20. Biochemical Marker
• Isozymes – fingerprinting and genetic diversity studies
(Hussain et al., 1987; Ramirez et al., 1987; Ocampo et al.,
1992; Lefevere & Charrier., 1993a)
• Applied to characterizing relationships among cassava
accessions (Lefevere & Charrier, 1993b; Wanyera et al.,1994)
• Alpha & beta esterase more informative,provide 22
alleles, which have complemented morphological
descroptors for identification of duplicates in cassava
germplasm (Ocampo et al., 1995)

21. Molecular / DNA Marker
• Independent to environment
• Stable
• Important to study the genes, genomes, and
genetic diversity.

22. Development of DNA markers
1st generation DNA markers
• RFLP (Grodzicker et al., 1974)
• VNTR (Jeffrey’s et al., 1985)
• ASO (Saiki et al., 1986)
• AS-PCR (Saiki et al., 1986)
• OP (Beckmann, 1988)
• SSCP (Orita et al.,1989)
• STS (Olsen et al., 1989)

23. 2nd generation DNA Markers
• RAPD (Williams et al., 1990)
• AP-PCR (Welsh and Mc Cleland, 1996)
• STMS (Becknann& Soller, 1990)
• RLGS (Hatada et al., 1991)
• CAPS (Akopyanz et al.,1992)
• DOP-PCR (Teknins, 1992)
• SSR (Akkaya et al., 1992)
• MAAP (Caetano-anolles et al., 1993)
• SCAR (1993)

24. New generation markers
IRAP ( 1998 )
REMAP ( 1999 )
MSAP ( 1999 )
MITE ( 2000 )
TE – AFLP ( 2000 )
IMP ( 2001 )
SRAP ( 2001 )
Others
۩ ISSR ۩ SAMPL ۩ AFLP/SRFA ۩ ASAP
۩ CFLP ۩ ISTR ۩ SSAP ۩ RBIP

25. Molecular / DNA Markers used in Cassava
• RFLPs (Botstein et al., 1980)
• SSRs (Litt & Lutly, 1989a,b)
• RAPDs (Williams et al., 1990)
• Minisatellites (jeffreys et al., 1993)
• AFLPs (Vos et al., 1995)

26. Relationship analysis of closely related species to
cassava based on microsatellite PCR’
To study phylogenetic relationship between cassava
and its closely related species from south America
Manihot esculenta ssp esculenta
M. esculenta ssp flabellifolia
M. esculenta ssp peruviana
M. pilosa
M. triphylla

27. Contd…
Multilocus markers are used
RAPD, AP-PCR, DAP, AFLP, & SSR
Recently oligonucleotide based SSR used
Two kinds of SSR data
Sequence data base
Specific genomic libraries

28. Contd…
Result
• Varied amplification
• No of band is varied from 1 – 15
• Fragment size varied from 200 – 3000 bp
• Scored as dominant marker
• Highest genetic diversity observed in M. esculenta ssp.
Flabellifolia followed by, M. esculenta ssp esculenta,
M. pilosa, M. esculenta ssp peruviana, M. triphylla

29. • CMD resistance conferred by dominant gene
• BSA – Identify a SSR markers linked to the CMD
resistant gene
• 186 SSR markers are used

30. Contd…
• Resistant gene – CMD 2
• Flanked by SSRY28 & GY1 @ 9 and 8cM respectively
• CMD resistant cassava – TME 3 X TMS 30555
• 158 individual was established invitro from embryo axes the
sub cloned
• Transfer the plants into a field with low CMD pressure
• CMD resistance evolved at 3 to 6 month old plant
• Scoring – 1 to 5

31. Genetic mapping of a CMD resistant gene
• 186 SSR markers – 80 SSR markers map positions
are known
• SSRY28 differentiate the CMD resistant genotype
from CMD susceptible genotype
• SSRY28 located on 17th chromosome of male-
parent-derived molecular genetic map
• Flanked by GY 1 & Ail 9b markers

33. Result
• All 10 plants of each resist genotype in all 3
replication are showed without any visible
symptoms
• Susceptible genotypes are always heavily infected
• SSRY 28 present in resistant genotypes and not in
susceptible genotypes.

34. • Most popular
• Dormaa, Wenchi, Nkoranza,& Asonafo
• 50 Genotypes are taken
• 4 primers (OPK-01, OPR-02, OPR-09, IOJ-14)
• 41 different bands detected
• Range of polymorphism % is 90% - 100%

37. 67 unlinked SSR loci assessed
283 accessions
Grouped into 14

42. 76 varieties are grown in Rewa
31 varieties – taken for AFLP analysis with some wild species
To assess:
Intravarietal diversity
Genetic variability in the local varieties

44. 78 accessions evolved
• 1- breeding stock (clone 58308)
• 5- improved lines
• 10 - CMD susceptible
• 62 - CMD resistant
36 SSR Markers are used

47. Institutes
• CIAT - Colombia
• IITA - Nigeria
• CDH - Africa
• CTCRI - India, Indonesia, Tanzania
• ESARC - Africa
• INEAC - Belgian Congo
• IRAT - West and Central Africa
• IRAM - Madagascar
• MARDI - Malaysia
• IICA - Venezuela, Mexico, Brazil,
Colombia, Costa Rica