Floral biology in relation to hand pollination of white yam

Abstract

Flowering behaviour and the morphology of flowers in white yam,Dioscorea rotundata Poir. is described in relation to hand pollination. Plants flowered between June and September with flowering intensity depending largely on factors associated with shoot vigour in genotypes. The high predominance of male plants coupled with irregular flowering necessitate the establishment of many plants to ensure sufficient flowering individuals for a hybridization programme. In order to achieve good fruit set and seed yields, pollen should be collected from open male flowers around 14.00 h and mature female flowers pollinated within a week after they are bagged particularly during the early flowering months. Low fruit set in white yam (12%) is primarily due to inefficient pollination by insects. With hand pollination fruit set is improved three-fold.