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.