Etiology of sprouting in purple yam (Dioscorea alata L.) tubers
2002
Quevedo, M.A. (Leyte State Univ., Baybay, Leyte 6521-A (Philippines). Philippine Root Crop Research and Training Center Bautista, O.K.
Purple yam, locally called ube, is used to provide color and flavor in ice cream and other food products and occasionally used as a staple food in the Philippines. Despite its importance, supply of good-quality tubers is a problem due in part to lack of planting materials. Whole tubers are bulky to use as a propagating material and only 1-2 sprouts appear from one tuber. Unlike potato, there are no buds or nodes identifying where the new plants will arise, except at the topmost part. Therefore farmers utilize whole small tubers or the uppermost part of big tubers as propagating material or seedsett to make sure that sprouts will arise. There is no study yet on the origin of the sprouts and factors affecting sprout formation in purple yam, hence this study. Sprouts can arise from any piece of a tuber that is cut even as small as 2.5 g. Low percentage sprouting was obtained from 2.5 g and 5 g pieces compared to 10 g seedsetts. Seedsett size that could result in 100% sprouting was 50 g. Longer and earlier sprouts arise in seedsett nearer the stem end because the cells are older. Seedsetts that were allowed to lose water to a moisture content of about 60% before planting sprouted better and earlier. Generally, the sprout comes out in the upper one third part of the seedsett, that is, the part toward the stem end, regardless of its size and the portion of the tuber from which they were cut. Seedsetts cut horizontally had higher percentage sprouting than those cut vertically. Tubers can be cut into 8-10 g or heavier pieces to give satisfactory sprouting. One kg tuber therefore can be a source of 112 seedsetts with more rapid sprouting of seedsetts taken from the upper part of the tuber
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