Variations in microtuber formation among accessions of D. alata and D. rotundata plantlets conserved at IITA's Genetic Resources Center

The conservation of yam genetic resources using field genebanks, in vitro plantlets, pollen and seed storage are constrained by high losses and space requirements, maintenance cost and an irregular flowering, respectively. Microtubers produced from in vitro plantlets are proposed for conservation, as they have a longer shelf-life due to dormancy, and are also hardier and less bulky than plantlets. This study evaluated microtuber formation by in vitro plantlets of 65 and 320 accessions of D. alata and D. rotundata. Plantlets were evaluated for six microtuberization (MTZ) traits using the nested design. Data were subjected to ANOVA and regression at p=0.05 while accessions were clustered using the fastclus procedure of the SAS. Means were separated. Accessions of each species differed for all traits, while species differences were insignificant for MTZ frequencies. High root vigour increased MTZ frequencies in both species, but for D. rotundata, high shoot vigour reduced MTZ frequencies. Out of the 65 accessions of D. alata, 27 (equivalent to 41.54%) and 173 out of 320 D. rotundata accessions (equivalent to 54.06%) had at least 50% tuberization. Half of the accessions of both species had less than 10% tuberization. Microtuber production could be a viable strategy in yam germplasm conservation and propagation especially when dormancy can be adequately controlled.