SEROLOGICAL DETECTION OF SEED-BORNE COWPEA VIRUSES IN UGANDA

Robert Amayo

Authors

Item 5

Research Objectives

Research Methodology

Content of Presentation

Research Background

Research Results and Discussion

Conclusion and Recommendation

Item 1

Item 2

Item 3

Item 4

Item 5 Acknowledgement

Research Background

• Production level and yield of the crop has continued to be low• Biotic factors are major contributors to the above.

• Cowpea production in Uganda ranks 3rd after beans and groundnuts.• 90% of the crop is grown in Semi-arid region of the country.

• 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.

• 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 ObjectivesTo estimate the prevalence and relative importance of viruses causing diseases in cowpea fields in Uganda.

Through:

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.

Research MethodologyField survey and sample collection

Symptom Expression

• 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.

Research Methodology cont’dLaboratory Work

The presence of 9 cowpea viruses were assessed namely; CMV, CPMMV, CPMoV, CCMV, CYMV, CPSMV, CABMV, SBMV and CPMV

• 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.

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

Incidences of cowpea viruses detected in leaf and seed samples collected from farmers’ fields in Eastern and West Nile regions of Uganda

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200

500

1000

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.

Virus and combinations

Yield and yield components* Percentage reduction in yield and yield components

Ht/cm at 5 WAE

No. of pods/ plant

No. of seeds/ plant

Yield(g) / plant RAUDP

C

Ht/cm at 5 WAE

Number of Pods/

plant

No. of seeds/ plant

Yield (g) / plant

Healthy (Control) 59.75 5.92 74.83 9.10 0.01 0.00 0.00 0.00 0.00CMV 46.67 1.75 25.75 3.05 0.20 21.89 70.42 65.59 66.48CPMMV 54.50 1.58 21.08 2.48 0.17 8.79 73.25 71.83 72.75CPMoV 49.92 1.75 21.42 2.35 0.08 16.45 70.42 71.38 74.18CCMV 65.25 2.58 32.75 3.65 0.27 -9.21 56.35 56.23 59.89CYMV 63.42 2.92 37.42 4.46 0.19 -6.14 50.70 49.99 50.99CPMV 57.92 2.33 30.75 3.72 0.20 3.06 60.57 58.91 59.12CABMV 39.75 1.25 13.50 1.49 0.20 33.47 78.87 81.96 83.63CMV+CPMMV 51.58 2.17 27.33 3.05 0.31 13.67 63.38 63.48 66.48CMV+CPMoV 42.17 1.33 19.33 2.34 0.23 29.42 77.47 74.17 74.29CMV+CCMV 50.25 1.67 23.58 3.04 0.16 15.90 71.83 68.49 66.59CMV+CABMV 43.58 1.50 21.33 2.54 0.22 27.06 74.65 71.50 72.09CCMV+CPMoV 49.67 1.83 24.67 3.24 0.23 16.87 69.02 67.03 64.40CABMV+CPMoV 50.50 1.83 23.92 2.92 0.26 15.48 69.02 68.03 67.91CCMV+CPMoV+CMV 45.00 1.25 19.50 2.95 0.43 24.69 78.87 73.94 67.58CMV + CPMoV + CABMV 48.92 1.58 21.58 3.02 0.36 18.13 73.25 71.16 66.81CMV + CPMMV + CCMV 52.83 1.67 25.17 3.13 0.40 11.58 71.83 66.36 65.60CPMMV+ CPMoV + CCMV 47.50 1.08 14.92 2.05 0.36 20.50 81.70 80.06 77.47CMV + CPMoV + CYMV + CCMV

52.33 1.42 21.83 3.12 0.26 12.42 76.05 70.83 65.71

CCMV+CMV+CPMoV+CABMV 43.67 1.50 19.67 2.77 0.30 26.91 74.65 73.71 69.56CCMV+CYMV+CABMV+CMV 31.67 0.67 8.83 1.08 0.43 47.00 88.73 88.20 88.13F. probabilityGrand mean

<0.00149.85

<0.0011.88

<0.00125.20

<0.0013.12

<0.0010.25

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.

Cowpea Variety Yield and yield components*

Plant height (cm) at 5 WAE

No. of pods No. of Seeds

Yield (g) RAUDC

Ichirikukwai (Ich)

46.78 1.32 16.64 2.04 0.31

Ebelat (Ebe) 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 meanF. prob.

49.850.005

1.88< 0.001

25.20< 0.001

3.120.001

0.25< 0.001

Variation in yield and yield components of cowpea varieties inoculated with different virus combinations.

Cowpea viruses *

Number of infected seeds

planted

Number of seedlings Seed transmission

(%)Tested infected

CMV 110 87 20 23.0

CPMMV 165 133 27 20.3

CABMV 75 67 11 16.4

Seed transmission levels of CMV, CPMMV and CABMV detected in seed samples from farmers’ fields in Uganda.

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 seed-borne viruses.

There is need for the production and use of virus-free seed, breeding for virus resistance and adoption of efficient seed certification systems.

Conclusion and Recommendations

Acknowledgement

DANIDA

THANK YOU!!