Yam (Dioscorea alata L.) microtuber formation in Temporary Immersion System as planting material

yam microtuber formation was developed in two culture stages. the type of culture system was defined and culture conditions were determined for microtuber formation, besides, the response of microtubers used as planting material in field conditions was evaluated. evaluations of morphological and physiological indicators determined to use the temporary immersion system during plant growth and microtuber formation stages. with an immersion time of 15 minutes every six hours, in 60 ml culture medium per in vitro plant and four culture medium renewals, 355 microtubers with a fresh weight equal or higher than to 0.5 g per temporary immersion system were formed. of these microtubers, 317 showed a fresh weight higher than 1.0 g and 121 of them presented a fresh weight equal or higher than 3.0 g. microtubers were directly planted in field conditions, although those with a fresh weight equal or superior to 3.0 g presented the highest sprouting (91.30%) and survival (96.50%) percentages. such plants showed the best responses in quantitative characters evaluated in the field. starting from these results, a scheme for microtuber production in temporary immersion system was proposed, as well as the use of microtubers as direct planting material in field conditions.