Sweet-potato improvement in Rwanda
1982
Janssens, M.J.J. (Institut des Sciences Agronomiques du Rwanda, Butare)
Sweet potato is a staple food throughout most of Rwanda, but production is hampered by viruses, weevils, leaf caterpillars, environmental heterogeneity, the late maturity of the crop, intergenotypic competition, and taste requirements. These constraints are the focus of the sweet-potato-improvement program in Rwanda. A main breeding population was established for evaluation of yield potential under mid-elevation Rwandan conditions, and sub-populations were used for trials on drought and cold stress. The procedure comprised selection, preliminary yield trials, multilocality yield trials, and preextension trials. In trials so far, tuber yield was highly correlated with number of tubers, and top growth was an indicator of yield quality (high starch and dry-matter content). Saccharose and starch were negatively correlated. One superior clone, Rusenya, yielded 8.1 x 10 (3) kg/ha on average across seven environments. Groups of varieties with similar environmental adaptability could be identified. A system of multireciprocal recurrent population improvement is proposed that consists of a central breeding population, aimed at high and stable yield, and a set of interdependent breeding subpopulations corresponding to particular breeding goals.
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