Abstract

A new method made up of different steps was established for micropropagation ofDioscorea alata. First plantlets were regenerated from shoots proliferating on nodal cuttings cultured on half strength Murashige and Skoog salt medium (MS/2) (basal medium) supplemented with 0.5 mg l^-1 BAP and 1 mg l^-1 NAA. These plantlets were used to induce microtubers on the basal medium supplemented with 1 to 5 mg l^-1 6-benzylaminopurine (BAP), kinetin (Kin) or α-naphthalene acetic acid (NAA) and 10 to 60 g l^-1 sucrose. BAP at 2 to 3 mg l^-1 combined with 20 to 30 g l^-1 sucrose was more effective than Kin and NAA. It gave rise to 92% plantlets producing microtubers and the highest numbers of microtubers per plantlet varied between five and six. Microtubers, when sectioned and cultured on the basal medium supplemented with different BAP/NAA or Kin/NAA ratios, differentiated into shoots that, when isolated and subcultured in the same media, gave rise to rooted plantlets. The highest percentage of microtubers that differentiated into shoots was 98.8%, the highest number of shoots per microtuber was 7.5 and hence the highest number of rooted plantlets regenerated from those shoots was induced with BAP/NAA ratio (3/2 mg l^-1)compared to that of BAP/NAA and Kin/NAA ratios. When the plantlets were acclimatized in different substrates, 97% survived in the mixture black soil/sand at equal volume (V/V) and this was the best result for the final step of the micropropagation of D. alata in this study. The different steps here described, allowed the regeneration of 45 and 16 plantlets from microtubers in about 251 days using BAP and NAA, respectively, and constituted a new and rapid method for the production of healthy seeds of this species.

Key words:  Growth regulators, micropropagation, microtubers, yam.

Abbreviation

2,4-D, 2,4-Dichlorophenoxy acetic acid; BAP, 6-benzylaminopurine;IBA, indole -3-butyric acid; Kin, Kinetin; MS, Murashige and Skoog; NAA, α-naphthalene acetic acid.