PLANTLETS FRONT ENCAPSULATED MICROPROPAGATED BUDS OF M.26 APPLE ROOTSTOCK

In order to be considered usable as synthetic seeds, encapsulated expl ants sown under in vitro or ex vitro conditions must be able to produc e whole plantlets. Ninety percent of non-encapsulated M.26 apple roots tock single nodes produced a plantlet (i.e., a well-formed shoot with a root system) after 30 days of culture in vitro if the explants were previously given a 24-hour treatment with 24.6 mu M IBA and 15 g l(-1) sucrose in darkness. In contrast, when the single nodes were encapsul ated in a calcium-sodium alginate bead immediately after the same trea tment only 10% of the encapsulated explants formed a plantlet. Additio n of growth regulators to the artificial endosperm and culture of the single nodes for root primordia initiation for 3, 6 or 9 days in darkn ess before encapsulation allowed production of 58%, 60% and 66% of pla ntlets, respectively.