Genomic analysis of Sweet potato feathery mottle virus from East Africa.

Sweet potato feathery mottle virus is a potyvirus that infect sweet potato. The genome of the virus was analysed to understand genetic diversity, evolution and gene flow. Motifs, nucleotide identity and a phylogenetic tree were used to determine phylogroup of the isolates. Gene flow and genetic diversity were tested using DnaSP v.5. Codons evolution were tested using three methods embedded in Datamonkey. The results indicate occurrence of an isolate of phylogroup B within East Africa. Low genetic differentiation was observed between isolates from Kenya and Uganda indicating evidence of gene flow between the two countries. Four genes were found to have positively selected codons bordering or occurring within functional motifs. A motif within P1 gene evolved differently between phylogroup A and B. The evidence of gene flow indicates frequent exchange of the virus between the two countries and P1 gene motif provide a possible marker that can be used for mapping the distribution of the phylogroups.

Farmers' practices and their knowledge of biotic constraints to sweetpotato production in East Africa.

Sweetpotato (Ipomoea batatas) is a vital crop for overcoming food insecurity in sub-Saharan Africa and its production is highest in East Africa where yields are high and the growing seasons are short. This cross-country study assessed farmers' local practices and their knowledge of the biotic constraints to sweetpotato production in Uganda, Rwanda, Kenya and Tanzania with the aim of providing empirical data that can ultimately be used to enhance sweetpotato production in these four countries. We collected data from 675 households using a standardized questionnaire integrated with a web-based mobile app. Survey results provided strong evidence that sweetpotato is valued as an important subsistence crop among smallholder farmers on pieces of land of less than 0.4 ha, and we observed that females were more involved than males in sweetpotato production. Sweetpotato was ranked as the second most important staple crop after cassava. Farmers noted an increase in sweetpotato production over the past five years in Uganda and Kenya but a decrease in Rwanda and Tanzania; the proportion of farmers who reported a decrease (33%) and an increase (36%) did not significantly differ. The main constraints to production were reported to be pests (32.6%), drought (21.6%), diseases (11.9%) and lack of disease-free planting materials (6.8%). Farmers recognized the signs and symptoms associated with sweetpotato diseases on leaves, root tubers, and whole plants, but most were unable to assign the disease type (bacterial, fungal or viral) correctly. We suggest that regional governments improve education, increase the provision of clean planting materials and strengthen breeding programs to improve disease resistance.