Evaluation of six cultivars of white yam (Dioscorea rotundata) across three yam-growing areas in southeastern Nigeria

Abstract

SUMMARYA split split-plot experiment was conducted in the 1986 and 1987 cropping seasons in three major yam-growing areas in southeastern Nigeria to assess the performance and yield stability of six cultivars of white yam (Dioscorea rotundata Poir). Location, fertilizer and cultivar, as well as some of their interaction effects, significantly affected tuber yields.The best location for yam production, based on the overall performance of the cultivars, was the sub-humid Guinea savanna, followed by the humid forest-regrowth and then the transitional forestsavanna zone. Except for two cultivars, which performed best in their source locations, all other cultivars yielded best at a different location. Thus, at present, these cultivars are not grown in those areas to which they are best suited. This makes it desirable to test exogenous cultivars in new areas. In terms of yield stability, however, the two cultivars originating from the humid forest-regrowth area gave the most stable yields across the three diverse environments considered. Although they did not give the highest tuber yields at all the locations, their overall yields were above the mean yields forall the cultivars. The most suitable cultivars were recommended for each ecological zone, on the basis of the observed interaction effects.