HIGH FREQUENCY SHOOT REGENERATION FROM LEAVES OF THE APPLE ROOTSTOCK M26 MALUS-PUMILA MILL

Regeneration of shoots was achieved from in vitro leaves of M26 at frequencies close to 100% on a medium based on MS salts and LS vitamins, containing 4.4 .mu.M BA and 0.5 .mu.M NAA. Dark and red light gave the best results in inducing shoot regeneration. White light at high intensity helped development of regenerated shoots. Inorganic nitrogen could be reduced by 75% without negative effect, and the presence of NH4+ was necessary for regeneration. Leaves were able to regenerate after a 3 kR irradiation (gamma rays), not after 4 kR. Optimal dose should be between 1 and 2 kR.