expressing the coat protein gene of cowpea aphid-borne
mosaic potyvirus predominantly convey the delayed symptom
R. Mundembe1,2*, A.
Matibiri3 and I. Sithole-Niang2
of Applied Biology, Kigali Institute of Science and
Technology, Avenue del’Armee, B. P. 3900, Kigali, Rwanda.
of Biochemistry, University of Zimbabwe, P. O. Box MP 167,
Mt Pleasant, Harare, Zimbabwe.
Section, Tobacco Research Board, Airport Ring Road, P. O.
Box 1909, Harare, Zimbabwe.
*Corresponding author. E-mail:
Phone: 0025003605195. Fax: 00250571927.
Cowpea aphid-borne mosaic virus (CABMV) is a potyvirus that
infects cowpea causing significant yield reduction. However,
there is no durable natural resistance to the virus within
the crop and genetic engineering for virus resistance was
not possible because of a lack of an efficient, reliable and
reproducible cowpea transformation and regeneration
protocol. Coat protein-mediated resistance to CABMV was
evaluated in Nicotiana benthamiana, a model host for
the virus. The CABMV coat protein gene from a Zimbabwean
isolate of the virus was optimised for expression in plants
under a CaMV 35S promoter and cloned into the Hind III site
of the binary vector plasmid pBI121 to result in the plasmid
pBI121-CPk. The plasmid pBI121-CPk was
used in Agrobacterium-mediated transformation of
N. benthamiana leaf sections following the
co-cultivation method. Regenerated plants were analysed by
PCR and Southern blot hybridisation. R1 seedlings were
assayed for kanamycin resistance and for presence of the
coat protein and challenged with CAMBV-infected sap. Lines
showing delayed symptom development were identified but no
line showing immunity was identified. Delayed symptom
development is significant resistance since it affords
protection to the plants during the crucial early stages of
development and exerts little evolutionary pressure on the
virus to evolve new strategies.
Cowpea aphid-borne mosaic virus, coat protein-mediated