Kingdom : PlantaeDivision : MagnoliophytaClass : magnoliolpsidaOrder : MalpighialesFamily : EuphorbiaceaeSubfamily : CrotonoideaeTribe : ManihoteaeGenus : ManihotSpecies : M. esculenta

Taxonomy

Origin – Brazil

Highly cross pollinated crop

Duration – 7 months to 2 years

Introduced to Africa and Asia from south America

Grown in 90 countries

Introduction

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

Contd…

- Best and Henry, 1992

Roots are mostly contain carbohydrates

Also rich in vit.C, carotene, Ca, and K

Poor in protein

Rich in protein and vitamins

Consumed as a vegetable

Biochemical aspects

Leaf:

Contd…

Root:

2n = 36

Genome size - 1.67 pg

772 M bp in the haploid genome

Genome structure

Brazil – 1,340 accessionsColombia - 2,003 accessions

World germplasm collection held at CIAT, Colombia

Has around 5,724 accession

Kenya Uganda Rwanda Burundi Congo

Madagoscar

Germplasm

Wild species

Manihot anomala

M. caerulescence

M. epruinosa

M. flabellifolia

M. glaziovii

M. dichotoma

M. tristis

M. peruviana

M. maracasensis

Paper industries

Textiles

Pharmaceuticals

Animal feed

Sago industries

Starch as raw material for

and also used as a poultry feed

Uses

Phenotypic marker

Graner (1942) described two morphological markers

Hershey & ocampo (1989) described eight morphological markers located on the stem, leaves, and root.

Markers

Leaf shapeRoot colour

cassava phenotypic markers

Organs Types

Plant shape1. Erect2. Tall and spread3. Spread

Colour of the young part of the stem

1. Green2. Yellow-green3. Green and beginning of petiole red4. Green and beginning of petiole red with red ribs

5. Green and red in equal area6. Some traces of green7. Entirely light red

Colour of the eye (bud)

1. Green2. coloured base and green scales3. Green base and coloured scales4. Entirely coloured

Emergence of eye (bud) 1. Deep2. Projecting

Alignment of internodes (young part)

1. Zigzag2. Straight

leaf shape 1. Palmipartite (normal shape)2. Palmisequate (the lobes totally

separate)

Coloration of petiole

1. Entirely green2. Yellowish green3. Vivid red4. Purple red5. Entirely purple

Number of leaf lobes1. Less than 32. 3 to 53. 5 to 74. 7 to 9

Shape of lobes

1.Very narrow2.Parallel edge3.Normal4.Wide5.Rounded with two widening

points

Form of lobes defined by position of maximal widening point

1.Proximal2.Median3.Terminal

Coloration of upper surface of lamina

1.White without chlorophyll2.Light green3.Yellow-green4.Dark green5.Purplish

Coloration of underside of lamina

1.Green2.Whitish-green3.Yellow-green 4.Purple of red

Coloration of lamina nerves

1.Always green2.red of upperside of young leaves3.red on underside of young leaves4.red on both side of young leaves

Leaf variation

Stem variation

Tuber variation

Forms of sepals

1. Wide

2. Medium

3. narrow

Sepals colour in female

flower

1. Entirely green

2. Green and coloured nerve

3. Red and green

4. Red to purple

Shape of 6 wings on the

ovary with 3 carpels

1. Always straight

2. Straight then sinous at maturity

3. Sinous then straight at maturity

4. Always sinous

Ovary body colour 1. Green

2. Red

Inflorescence

Root

Length of root

1. Short ( < 40 cm )

2. Normal ( 40 to 80 cm )

3. Long ( > 80 cm)

Shape of root

1. Conical

2. Fusiform

3. Cylindro-conical

4. cylindrical

Texture of root surfaces

1. Smooth

2. Medium

3. Rough

Appearance of external bark

1. Grey and thin

2. Brown and thick

Colour of pulp 1. White

2. Yellow

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)

Molecular / DNA Marker

Independent to environment

Stable

Important to study the genes, genomes, and genetic diversity.

Development of 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)

1st 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)

2nd generation DNA Markers

IRAP ( 1998 )

REMAP ( 1999 )

MSAP ( 1999 )

MITE ( 2000 )

TE – AFLP ( 2000 ) IMP ( 2001 )

SRAP ( 2001 )

New generation markers

۩ ISSR ۩ SAMPL ۩ AFLP/SRFA ۩ ASAP ۩ CFLP ۩ ISTR ۩ SSAP ۩ RBIP

Others

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)

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 esculentaM. esculenta ssp flabellifoliaM. esculenta ssp peruvianaM. pilosaM. triphylla

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

Contd…

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

Contd…

Result

CMD resistance conferred by dominant gene

BSA – Identify a SSR markers linked to the CMD resistant gene

186 SSR markers are used

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

Contd…

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

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.

Result

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%

67 unlinked SSR loci assessed

283 accessions

Grouped into 14

76 varieties are grown in Rewa31 varieties – taken for AFLP analysis with some wild speciesTo assess:

Intravarietal diversity

Genetic variability in the local varieties

78 accessions evolved

36 SSR Markers are used

1 - breeding stock (clone 58308) 5 - improved lines10 - CMD susceptible 62 - CMD resistant

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

Institutes