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Improving and deploying markers for biotic stresses in cassava
GCP Project #: G7010.01.02
Chiedozie Egesi NRCRI, Nigeria
Biotic constraints of cassava in Africa Mapping and new QTLs for cassava mosaic disease
(CMD) Pyramiding of QTLs for CMD Validating QTLs for cassava brown streak disease
(CBSD) Mining for resistance genes for cassava bacterial
blight (CBB) and cassava green mite (CGM) Summary
Outline
Cassava brown streak disease Cassava bacterial blight
Cassava mosaic disease Cassava green mite
Each could cause yield losses of 30 to 100%
Major Biotic Constraints in African Cassava Productivity
To develop mapping populations for CMD
To identify and map QTLs for new sources of CMD
To develop populations for validation of QTLs for CBSD
To identify sources of resistance to CGM and CBB
Specific Objectives
New QTLs for CMD
Umudike: 97/2205 x 30555 N=340
Frequency distribution of severity scores for CMD in 2 mapping populations in Umudike and Otobi
Otobi: 96/1089A x 30555
Otobi: 97/2205 x 30555
Umudike: 96/1089A x 30555 N=141
Disease severity scores from 1 to 5. Plants with scores 1-2 are considered resistant.
Mean symptom severity scores for CMD in 2 mapping populations in Umudike and Otobi
Family Trial Severity scores of
parents Severity scores of
progenies 30555 97/2205 Check Lowest Highest F-value
97/2205x30555 Otobi 3 1 3.82 1 5 4.31***
N = 340 Umudike 3 1 2.76 1 4.04 2.72***
30555 96/1089A Check Lowest Highest F-value
96/1089Ax30555 Otobi 4 1 4.08 1 4 5.14*** N = 141 Umudike 2.6 1 2.5 1 4.08 1.39*
Linkage group size for SNP markers from family 97/2205 x 30555
Linkage group Number of markers
Average marker interval (cM)
Size (cM)
1 48 2.13 102.3 2 35 3.57 125.1 3 37 3.59 132.8 4 51 1.98 100.9 5 46 2.48 114.2 6 34 1.28 43.5 7 40 2.93 117.0 8 41 1.94 79.6 9 37 3.09 114.3
10 35 3.96 138.6 11 34 3.34 113.4 12 32 3.63 116.1 13 25 5.43 135.7 14 18 4.52 81.4 15 14 2.16 30.3 16 13 4.47 58.1 17 29 3.01 87.3 18 8 2.21 17.7
Total/Average* 577 3.1* 94.9*
SNP genetic linkage map of family 97/2205 x 30555
QTLs associated with resistance to CMD
Chr Position Left Marker Right Marker LOD
2 501 md076 md077 24.3743
4 1703 md168 md170 21.9322
8 636 md333 md334 18.4417
10 290 md402 md403 26.5707
13 358 md504 md506 23.5867
QTLs associated with resistance to CMD
Pyramiding of QTLs for CMD
Combining CMD2 and new QTLs to broaden resistance
Crosses derived from parents with new QTLs already being
phenotyped
ca. 100 progenies in multi-site trials for resistance to CMD
Integration of SSR and SNP maps and markers for
consensus maps/QTLs
Pyramiding of QTLs for CMD
Validating QTLs for CBSD
Populations developed and segregating for CBSD in Tanzania
Parents Number of F1 Seeds derived
Number of seedlings
established Resistant Susceptible Namikonga AR37-80 5551 621 Kiroba 3C83-13 926 334 Muzege Cheupe 657 111 B2C20-65 AR37-80 302 150 Total 7436 1216
Evaluation for the second year in Tanzania is nearing completion
Markers derived from a BMGF project to be used for validation
Frequency distribution for CBSD in 4 mapping populations
0
20
40
60
80
100
120
1 2 3 4 5
Muzege x Cheupe CBSD 6 MAP
0
20
40
60
80
100
120
1 2 3 4 5
Muzege x Cheupe CBSD 3 MAP
0
20
40
60
80
100
120
1 2 3 4 5
B2C20-65xAR 37-80 CBSD 3 MAP
0
20
40
60
80
100
120
140
1 2 3 4 5
B2C20-65 x AR 37-80 CBSD 6 MAP
0
100
200
300
400
500
600
700
1 2 3 4 5
Namikonga x AR 37-80 CBSD 3 MAP
0
100
200
300
400
500
600
1 2 3 4 5
Namikonga x AR 37-80 CBSD 6MAP
0
50
100
150
200
250
300
1 2 3 4 5
Kiroba x 3C83-13 CBSD 3 MAP
0
50
100
150
200
250
300
1 2 3 4 5
Kiroba x 3C83-13 CBSD 6 MAP
0
20
40
60
80
100
120
1 2 3 4 5
Muzege x Cheupe CBSD 9 MAP
0
20
40
60
80
100
1 2 3 4 5
B2C20-65 x AR 37-80 CBSD 9 MAP
0
100
200
300
400
500
600
1 2 3 4 5
Namikong x AR 37-80 CBSD 9 MAP
0
50
100
150
200
250
300
1 2 3 4 5
Kiroba x 3C83-13 CBSD 9 MAP
Mining for resistance gene donors in African cassava to cassava bacterial blight (CBB) and cassava green mite (CGM)
1. Leaf blighting, brownish vascular discoloration
2. Wilting
3. Die back & rapid defoliation=‘candle sticks’
1, 3 2
1 1
4 5
Cassava Bacterial Blight (CBB)
CGM
Cassava green mite (CGM) symptoms
Field evaluation for two years
Multi-site, replicated trials
Germplasm assessed for resistance to CBB and CGM
Population Type
Number of Accessions
Trait Assessed
Landraces 256 CBB, CGM Improved 183 CBB, CGM Total 439
23.0
74.2
2.7
0.0
10.0
20.0
30.0
40.0
50.0
60.0
70.0
80.0
R MS HS
Freq
uenc
y (%
)
R = Resistant; MS = Moderately susceptible; HS = Highly susceptible
21.46
52.79
25.75
0.00
10.00
20.00
30.00
40.00
50.00
60.00
R MS S
Freq
uenc
y (%
)
CBB CGM
Distribution of 256 African casssava landraces for resistance to cassava bacterial blight (CBB) and cassava green mite (CGM)
13.4
59.3
27.3
0.0
10.0
20.0
30.0
40.0
50.0
60.0
70.0
R MS HS
Freq
uenc
y (%
)
30.2
46.1
23.5
0
5
10
15
20
25
30
35
40
45
50
R MS HSFr
eque
ncy
(%)
CBB CGM
R = Resistant; MS = Moderately susceptible; HS = Highly susceptible
Distribution of 183 improved casssava genotypes for resistance to cassava bacterial blight (CBB) and cassava green mite (CGM)
NRCRI germplasm
CBB score
CGM score
IITA germplasm
CBB score
CGM score
NR/8010 1 1 188/023543 1 1 74/2 1 2 189/00748 1 1 74/640 1 2 TME-226 1 1 73/30 1 2 T983/00016 1 1 73/192 1 2 188/01226 1 1 73/404 1 2 088/00623 1 1 75/647 1 2 TME-236 1 2 75/726 1 2 TME-478 1 2 77/169 1 2 088/00378 1 2 TMX4009 1 2 087/00183 1 2
Disease and pest severity scores on the basis of 1 to 5 where 1 is no symptom and 5 is very severe symptoms
Clones identified with combined resistance to cassava bacterial blight (CBB) and cassava green mite (CGM)
New mapping populations for CMD and CBSD formed and
evaluated
QTLs for resistance to CMD identified
Pyramiding of different sources of resistance to CMD
commenced
New sources of resistance to CGM and CBB identified
Summary
Acknowledgements
NRCRI, Nigeria
Emmanuel Okogbenin
Joseph Onyeka
Others
CRI, Ghana
Elizabeth Parkes
Bright Peprah
Others
ARI, Tanzania
Geoffrey Mkamilo
Heneriko Kulembeka
Others
GCP
Xavier Delannay
Chunlin He
Others
Project Partners
Thank You!
