Seed-borne viruses detected on farm-retained seeds from smallholder farmers in Zimbabwe, Burkina Faso, Bangladesh and Vietnam

The smallholder farming sector in much of the developing world
relies on the use of farm-retained seed. The availability of good
quality disease free seed is important in enhancing food security
but seed-borne viruses can be a major problem on farm-retained
seed. Seeds of tomato (Lycopersicon esculentum Mill.),
paprika (Capsicum annuum L.), cowpea (Vigna unguiculata
L. Walp), bambara [Vigna subterranea (L.) Verdc.] and
peanut (Arachis hypogaea L.) from smallholder farmers in
Zimbabwe, Burkina Faso, Bangladesh and Vietnam were tested
for seed-borne viruses using various techniques including
electron microscopy, Enzyme Linked Immunosorbent Assay
(ELISA) and biological assays. Tomato mosaic virus (ToMV)
was detected in 36% of tomato samples and in 8% of paprika
samples using indicator Nicotiana tabacum cultivars Xanthinc
and White Burley. Some 43% of cowpea samples were
infected with Cowpea aphid-borne mosaic virus (CABMV) and
7% were infected with the Blackeye cowpea mosaic strain of
Bean common mosaic virus (BCMV-BlCM). Peanut mottle
virus (PeMoV) was detected with an infection range of 5.4%-
12.5% in bambara samples tested using indirect antigen-first
ELISA, indicator IITA cowpea lines Tvu 3433, Tvu 1582, Tvu
401 and Tvu 2657 and Phaseolus vulgaris cultivar Topcrop.
No viruses were detected in the peanut samples. The lack of a
broad range of serological antisera limited the number of viruses
tested but results show that the bulk of the samples were
infected with seed-borne viruses. The results imply that
resources must be invested in improving the quality of seed
from the smallholder sector. National and international
germplasm collection centres should be equipped with capacity
to test for seed-borne viruses so as to minimize the movement
of infected germplasm in breeding materials or germplasm
exchange in international collections.