QUALITATIVE AND QUANTITATIVE PRODUCTION OF POTATO MICROTUBERS (SOLANUM-TUBEROSUM L) IN 2-PHASE SYSTEM

Potato microtubers obtained by in vitro culture on liquid media, prese nt hyperhydric formations, a physiological disorder of tissue-cultured plants. On the other hand, when microtubers are produced on solid med ia their weights is rather slow. The aim of this work was to avoid or to decrease these abnormalities without affecting microtubers weight. Nodal cuttings of cvs ''Spunta'' and ''Bintje'' were grown for 28 days on hormone-free Murashige-Skoog (MS) medium under 16 hs of photoperio d at 120 mu moles.m(2).s(-1) and 20-22 degrees C, then the solid propa gation medium was overlayered with different volumes of liquid MS or W hite-Nitsch-Morel (WNM) tuberization media supplemented with 10 g.1(-1 ) sucrose, 10 mg.1(-1) BAP and 600 mg.1(-1) of commercial cycocel. Pla ntlets were placed at continous darkness and 18-20 degrees C. Tuberiza tion percentages at 17 and 60 days from the beginning of the experienc e, microtubers weight, microtubers abnormal percentages, dormancy peri od and normal and abnormal microtubers weight loss after harvest were recorded. The present results indicate that a two-phase system (overla yering the 60 ml of solid propagation MS medium with 45 ml of modified MS tuberization liquid media) optimize the microtubers weight (769.5 mg for cv ''Spunta'' and 498.1 mg for cv. ''Bintje'') and decrease the percentages of the abnormalities for both cvs.