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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