SEROLOGICAL
DETECTION OF SEEDBORNE COWPEA
VIRUSES IN UGANDA
Robert Amayo
Dry Land Legume Program
National Semi-Arid Resources
Research Institute (NaSARRI),
Serere
Authors
Amayo
Robert
(MSc.)
Edema
Richard
(PhD)
Arinaitwe
Abel B.
(MSc.)
Rubaihayo
Peter R.
(DSc.)
Settumba
Mukasa
B. (PhD)
Tusiime
Geoffrey
(PhD)
Content of Presentation
Item 1
Research Background
Item 2
Research Objectives
Item 3
Research Methodology
Item 4
Research Results and Discussion
Item 5
Conclusion and Recommendation
Item 5
Acknowledgement
Research Background
• Cowpea production in Uganda ranks 3rd
after beans and groundnuts.
• 90% of the crop is grown in Semi-arid region
of the country.
• Production level and yield of the crop has
continued to be low
• Biotic factors are major contributors to the
above.
• Diseases caused by viruses can cause
up to 100% grain yield loss.
• This is exacerbated by lack of or limited
knowledge on presence of the diseases.
Research Objectives
To estimate the prevalence and relative
importance of viruses causing diseases in
cowpea fields in Uganda.
Through:
•
•
•
•
Assessed the incidence and severity of virus-like
diseases in cowpea fields
Identified cowpea viruses that are seed-borne
Evaluated the effect of the virus diseases on
performance of selected cowpea lines
Assessed the seed transmission potential of three
major seed-borne viruses.
Research Methodology
Field survey and sample collection
Two surveys were carried out two
growing seasons in 7 districts as
shown in the figure.
•
Disease incidence and severity
were scored as described
(Gumedzoe et al., 1997; Madden
and Hughes, 1999)
Leaf and seed samples were
collected From at least 10
cowpea fields per districts.
•
•
Sampling was carried out as
described by Nutter et al. (1997).
The samples were bagged
separately for further assessment
in the laboratory and
screenhouse.
Symptom Expression
Research Methodology cont’d
Laboratory Work
•
Double Antibody Sandwich Enzyme Linked
Immuno-Sorbent Assay (DAS-ELISA) was used for
diagnosis.
•
•
Viruses extracts from crushed leaf samples and
finely ground seed samples were detected as
described by Clark and Adams (1977) and
Koenraadt and Remeeus (2006), respectively.
A modified Reverse Transcriptase-Polymorphic
Chain Reaction protocol (Gillaspie et al., 2001)
was used to confirm the presence of three
most common viruses.
The presence of 9 cowpea viruses were assessed namely; CMV, CPMMV,
CPMoV, CCMV, CYMV, CPSMV, CABMV, SBMV and CPMV
Research Methodology Cont’d
Virus infection effects Study
•
•
Seedlings for 4 cowpea lines
grown in plastic pots were
inoculated with different viruses
and virus combination.
Disease data was collected 14
DPI till maturity.
Seed transmission potential study
•
•
Seed samples that tested positive for 3 most important
viruses were used.
2 - 3 seedlings were maintained per pot. 21 DPG, leaf
samples from seedlings assessed for the viruses. This was
repeated twice at 28 and 35 DPG.
Incidences of cowpea viruses detected in leaf and
seed samples collected from farmers’ fields in
Eastern and West Nile regions of Uganda
CPMV
CPSMV
CCMV
+
+
+
+
+
-
+
+
CPMoV
+
SBMV
CYMV
Eastern Region
CMV
Virus
Incidence
(%)
CPMMV
Viruses detected
CABMV
Location
Pallisa
73.6 (42.8)
16(6)
4(2)
22(2)
0(2)
7(4)
4(1)
0(0)
20(1)
16(2)
Kumi
72.7 (37.0)
27(3)
4(2)
24(1)
0(0)
11(8)
13(1)
0(0)
18(1)
13(3)
Soroti
87.5 (58.8)
20(4)
4(7)
13(3)
0(2)
11(5)
11(1)
0(0)
16(2)
11(3)
+
+
+
+
+
+
+
+
7(0)
9(0)
0(0)
2(0)
7(0)
West Nile
Nebbi
87.6 (0.0)
11(0)
2(0)
4(0)
0(0)
Arua
47.5 (36.4)
22(0)
0(4)
2(0)
0(0)
4(0)
4(0)
0(0)
20(0)
0(0)
Yumbe
48.6 (85.7)
2(0)
0(1)
2(2)
0(0)
2(0)
11(0)
0(0)
2(0)
0(2)
Moyo
73.6 (50.0)
7(0)
11(3)
18(4)
0(0)
7(3)
9(0)
1(0)
2(0)
9(1)
MUARIK
66.1 (96.7)
29(23)
6(7)
8(31)
0(0)
17(0)
9(0)
1(0)
18(0)
10(1)
F. Prob.
< 0.01
1
2
3
4
5
6
1000
500
200
RT-PCR gel picture: Lower bands in Lanes 3, 4 and 6 are for CABMV,
while the upper bands in lanes 2 and 4 are for CMV. Lane 5 is for a
negative control and lane 1 is 1kb size marker.
Effect of single and multiple virus infections on plant height,
number of pods, weight, and the RAUDPC of cowpea plants
grown in screen house at MUARIK.
Yield and yield components*
Ht/cm at
5 WAE
Virus and combinations
Healthy (Control)
CMV
CPMMV
CPMoV
CCMV
CYMV
CPMV
CABMV
CMV+CPMMV
CMV+CPMoV
CMV+CCMV
CMV+CABMV
CCMV+CPMoV
CABMV+CPMoV
CCMV+CPMoV+CMV
CMV + CPMoV + CABMV
CMV + CPMMV + CCMV
CPMMV+ CPMoV + CCMV
CMV + CPMoV + CYMV + CCMV
59.75
46.67
54.50
49.92
65.25
63.42
57.92
39.75
51.58
42.17
50.25
43.58
49.67
50.50
45.00
48.92
52.83
47.50
52.33
CCMV+CMV+CPMoV+CABMV
CCMV+CYMV+CABMV+CMV
F. probability
43.67
31.67
<0.001
No. of
pods/
plant
5.92
1.75
1.58
1.75
2.58
2.92
2.33
1.25
2.17
1.33
1.67
1.50
1.83
1.83
1.25
1.58
1.67
1.08
1.42
1.50
0.67
<0.001
No. of
seeds/
plant
74.83
25.75
21.08
21.42
32.75
37.42
30.75
13.50
27.33
19.33
23.58
21.33
24.67
23.92
19.50
21.58
25.17
14.92
21.83
Yield(g) /
plant
19.67
8.83
<0.001
2.77
1.08
<0.001
9.10
3.05
2.48
2.35
3.65
4.46
3.72
1.49
3.05
2.34
3.04
2.54
3.24
2.92
2.95
3.02
3.13
2.05
3.12
RAUDP
C
0.01
0.20
0.17
0.08
0.27
0.19
0.20
0.20
0.31
0.23
0.16
0.22
0.23
0.26
0.43
0.36
0.40
0.36
0.26
0.30
0.43
<0.001
Percentage reduction in yield and yield
components
Ht/cm at Number
No. of
Yield (g)
5 WAE
of Pods/
seeds/
/ plant
plant
plant
0.00
0.00
0.00
0.00
21.89
70.42
65.59
66.48
8.79
73.25
71.83
72.75
16.45
70.42
71.38
74.18
-9.21
56.35
56.23
59.89
-6.14
50.70
49.99
50.99
3.06
60.57
58.91
59.12
33.47
78.87
81.96
83.63
13.67
63.38
63.48
66.48
29.42
77.47
74.17
74.29
15.90
71.83
68.49
66.59
27.06
74.65
71.50
72.09
16.87
69.02
67.03
64.40
15.48
69.02
68.03
67.91
24.69
78.87
73.94
67.58
18.13
73.25
71.16
66.81
11.58
71.83
66.36
65.60
20.50
81.70
80.06
77.47
12.42
76.05
70.83
65.71
26.91
47.00
74.65
88.73
73.71
88.20
69.56
88.13
Variation in yield and yield components of cowpea
varieties inoculated with different virus combinations.
Cowpea Variety
Yield and yield components*
Plant
No. of pods No. of
height (cm)
Seeds
at 5 WAE
46.78
1.32
16.64
Yield (g)
RAUDC
2.04
0.31
50.51
1.76
22.94
2.86
0.22
Secow 2W (Sec)
50.16
2.14
30.54
3.65
028
FE 69 (Fe)
51.95
2.32
30.70
3.93
0.17
Average mean
F. prob.
49.85
0.005
1.88
< 0.001
25.20
< 0.001
3.12
0.001
0.25
< 0.001
Ichirikukwai
(Ich)
Ebelat (Ebe)
Seed transmission levels of CMV, CPMMV and
CABMV detected in seed samples from farmers’ fields
in Uganda.
Cowpea
viruses *
Number of
infected seeds
planted
Number of seedlings
Tested
infected
Seed
transmission
(%)
CMV
110
87
20
23.0
CPMMV
165
133
27
20.3
CABMV
75
67
11
16.4
Conclusion and Recommendations
Several viruses infect cowpea in Uganda and
a large number of them are seed-borne.

Multiple virus infections resulted in a significant
decrease in yield and yield components.

There
was no significant difference in the seed
transmission potential of three important seedborne viruses.
There is need for the production and use of
virus-free seed, breeding for virus resistance and
adoption of efficient seed certification systems.

Acknowledgement
DANIDA
THANK YOU!!