Micropropagation of yam

A more efficient tissue culture technique for the micropropagation of two major purple yam varieties, VU-2 and Kinampay was developed. Nodal explants from greenhouse-grown plants were used. Steps involved were: a) sterilized nodal segments to minimize culture contamination; b) Establish stockplants as source of clean propagules for multiplication; c) Optimize culture conditions to ensure high percentage plantlet production and reduce micropropagation costs; and d) Establish potting out procedure to ensure survival of plantlets prior to use as planting materials for field establishment. Findings showed that the use of benomyl as dip and two-stage calcium hypochlorite (CaOCl2) treatments proved to be the most effective tissue sterilization method to minimize tissue contamination. The Marashige and Skoog (MS) basal medium induced shoot and root development. Benzylaminopurine (BAP) and indole acetic acid (IAA) at 0.25-1.0 mg/L as medium additives did not improve shoot and root formation of VU-2 nodal cultures. Instead the number of shoots and roots forming cultures decreased and shoot and root development were delayed. In Kinampay nodal cultures, BAP and IAA did not induce root formation but increased the number of shoot-forming cultures and the number of shoots produced,particularly at lower concentration of 0.25 - 0.50 mg/L. Single nodal segments of the stockplants can be used as starting explants for multiplication. No added advantage was obtained with the use of bigger plants. Increasing the sucrose level of the MS medium from the usual 2-5% enhanced shoot and root development of Kinampay nodal cultures. Sucrose supplement had no effect on VU-2. The use of table sugar as sucrose substitute decreased micropropagation cost by about 18% while the use of agarite, agar-agar or food-grade gulaman as substitute for Sigma agar decreased micropropagation cost by 32%. Combined use of gulaman and table sugar further decreased micropropagation cost by 39% relative to the use of Sigma agar and sucrose. These substitute compounds has no adverse effects in plantlet production. A 90-100% plant survival can be achieve for VU-2 using either garden soil or combination of garden soil and river sand at 1:1 ratio as potting medium while for Kinampay, 85-90%. Plantlets can be potted out one month after incubation