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Groundnut rosette disease is the most destructive viral disease of peanut in Africa and can cause serious yield losses under favourable conditions. The development of disease-resistant cultivars is the most effective control strategy. Resistance to the aphid vector, Aphis craccivora, was identified in the breeding line ICG 12991 and is controlled by a single recessive gene. Bulked segregant analysis (BSA) and amplified fragment length polymorphism (AFLP) analysis were employed to identify DNA markers linked to aphid resistance and for the development of a partial genetic linkage map. A F(2:3) population was developed from a cross using the aphid-resistant parent ICG 12991. Genotyping was carried out in the F2 generation and phenotyping in the F3 generation. Results were used to assign individual F2 lines as homozygous-resistant, homozygous-susceptible or segregating. A total of 308 AFLP (20 EcoRI+3/MseI+3, 144 MluI+3/MseI+3 and 144 PstI+3/MseI+3) primer combinations were used to identify markers associated with aphid resistance in the F(2:3) population. Twenty putative markers were identified, of which 12 mapped to five linkage groups covering a map distance of 139.4 cM. A single recessive gene was mapped on linkage group 1, 3.9 cM from a marker originating from the susceptible parent, that explained 76.1% of the phenotypic variation for aphid resistance. This study represents the first report on the identification of molecular markers closely linked to aphid resistance to groundnut rosette disease and the construction of the first partial genetic linkage map for cultivated peanut.

Abstract AbstractThis study uses farmers who hosted on-farm trials and demonstrations involving three new groundnut varieties in Malawi to assess their acceptability and adoption potential. It also examines patterns of seed diffusion among trial farmers as well as among non-trial farmers who were members of seed banks. The study shows that trial follow-up surveys provide a cost-effective approach for assessing early adoption and providing feedback to researchers. Although this study is useful it needs to be perceived and designed as one of several studies that help researchers understand the complexity of farmers' adoption decisions. Résumé Résumé Résumé Résumé Résumé Evaluation du potentiel d'adoption de nouvelles variétés d'arachide au Assessing Adoption Potential of New Groundnut Varieties in Malawi

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Groundnut is an important food and cash crop in the Southern African Development Community (SADC ) region, and is grown largely by smallholder farmers under low input conditions. Constraints are many and varied, both between and within the member states, but diseases are generally regarded as major constraints to groundnut production throughout the region. A large number of fungal, viral, nematode, and bacterial diseases of groundnut have been reported. Most of the diseases are widespread, but only a few of them are economically important on a regional basis. In this paper, the current distribution and economic importance of leaf spots, web blotch, rust, gray mould, pod rots, blackhull, Sclerotinia blight, stem rot, seedling diseases, aflatoxin contamination, rosette, groundnut streak necrosis, pod nematode, and pod scab nematode diseases, and various options (chemical control, host-plant resistance and cultural practices) for their management, are briefly reviewed. Future research needs on groundnut diseases in the region are discussed.