Matsubara S. et al., Scientific Reports of the Faculty of Agriculture, Okayama University 79: 37-44 (1992)
Summary
Most Chinese yam 'Ichouimo' (Dioscorea batatus Decne.) plants are known to be infected with virus, because of their vegetative reproduction. In general, seed bulbs are expensive due to low multiplication. However, to increase bulb size and yield, it is desirable to produce virus-free plants. In the present pai?er, conditions for the propagation of desease-free bulbs by multiple buds culture were studied. Plants were grown on the basal medium consisted of Murashige & Skoog (MS) medium plus various combinations of gelling agents, phytohormones and various concentrations of sucrose and incubated at 25°C under 16h daylength supplied with 20 f.lmol/s/ m' of artificial light.
Formation of multiple buds: Aerial bulbils grown on nodule of plants were cultured on the basal medium, and shoots with 3 - 4 leaves grown on them were used to obtain explants. Each nodular sections with a lateral bud were dissected as explants and cultured on the aqueous basal medium with 20mg/ £ ancymidol for 47days. Multiple buds were formed on the medium.
Multiplication of multiple buds: Multiple buds were separated and cultured in the basal medium with or without lOmg/ £ ancymidol by rotary or shaking culture for 40days. Multiple buds were further multiplicated in all lots, and multiplicating rate was high in the basal medium with ancymidol by shaking culture.
Seven cycles of subcu,lturing of multiple buds: Multiple buds were separated to a sigle bud, and cultured in the aqueous basal medium containing lOmg/ £ ancymidol and 2 % sucrose by shaking. They were subcultured at the intervals of 46days. Multiplicating rate at every subculture were about 30 times constatly, and the multiplied buds were also in the smilar size.
Acclimatization of multiple buds: Each bud separated from multiple buds was cultured on the basal medium containing 0. 6 or 1 % agar, or 0 .lor 0. 2% gelrite for 10, 20 or 30days, and they were then acclimatized. Plantlets in all lots were survived. The longer the culturing period, the faster the rooting. Rooting of plantlets on the medium with gelrite was faster than that on the agar medium.
Aerial bulbi! (s) formation on plantlets: Each bud separated from multiple buds was cultured on the basal medium containing 0.2% gelrite and 3% sucrose. Two and a tenth minitubers per shoot were formed at nodal section or shoot base after 2 - 3 month at room temperature. In winter season, shoots were died, and sprouting from minitubers started in spring season. After shoots grew, new minitubers were formed at stem section and shoot base. Plantlets of 307 were multiplicated from one bud by multiple buds culture and three minitubers were formed from one shoot during one year.