Abstract
Glasshouses have been used to induce flowering in sweetpotatoes for the purpose of breeding. However, these structures are expensive to construct and/or maintain. This study investigated the effects of staking the sweetpotatoes in the field as a way of flower induction for purposes of pollination and testing cross-compatibility in sweetpotato. Two field experiments (staking and non-staking) were carried out at Ibadan from May 2010 and April 2011 using a randomized complete block design with three replicates. In the first experiment (non-staked), vine cuttings of 39 parent clones were evaluated for flowering while staking was done for the second experiment, which was also used as a crossing block. Vine cuttings of the 39 parent clones were planted on heaps at 1 m ×1 m with two 25 cm cuttings per heap, staked with 2 m wooden poles. The main vines were tied and trained up the stakes to induce flowering. Clones that flowered were crossed in a diallel. Dried fruits were harvested between 30 and 50 days after pollination. Seeds from these fruits were soaked in water and planted in polythene bags filled with top soil to test their viability. Results from these studies showed that 18 out of 39 clones readily produced flowers and that staking increased the number of flowers produced. Blesbok and 440168 clones had longer anthers than their stigma while it was the opposite in the other clones. In clone 440034 the anther and stigma were at the same height. Of the 324 cross-combinations conducted on the 18 clones that flowered, only 109 produced seeds. The mean percentage cross-compatibility for the 18 clones was 44.3%. Compatibility varied considerably among the clones ranging between 5.4% and 68.7%, with clone W-151 showing the highest level (68.7%). All flowering clones were observed to be self-incompatible except for clones Sauti and TIS 8441. The hybrid seeds obtained from the flowering clones had a mean percentage germination of 50.6%. These data suggest that stakes induced flowering in 18 parent stocks and therefore can be used to facilitate hybridization in sweetpotato for improved hybrid seed production. However, further work is needed to enhance success in flowering of clones.