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Interviews identified that most small-scale maize farmers in central Uganda and in the Southern Highlands of Tanzania plant home-saved seed of landraces or seed derived from various open-pollinated and hybrid varieties. Some farmers also bought a portion of their seed, either certified seed, locally traded seed or even maize sold for consumption. Selection for home-saved seed was generally among harvested cobs. Big cobs with many, regularly arranged, large, white, flint kernels were preferred. A maize cob may bear several hundred seeds, so a farmer needs to save <1% of cobs for seed. A form of resistance in which plants show only moderate symptoms and suffer only a small reduction in yield when infected has been incorporated in some released varieties. Because not all plants in most crops are infected and because plants uninfected with Maize streak virus (MSV) tend to produce bigger cobs than infected resistant plants, the few cobs selected by a farmer for seed may all be from the uninfected ‘escapes’, with no preferential selection of resistant types. On-station simulation of the farmers’ selection process in a crop of the MSV-resistant maize variety, Longe 1, confirmed this. An alternative very strong form of MSV resistance was identified. [ABSTRACT FROM AUTHOR]