SHOOT TIPS OF WHEAT AS AN ALTERNATIVE SOURCE FOR REGENERABLE EMBRYOGENIC CALLUS-CULTURES

Shoot tips of Triticum aestivum L. cvs. Turbo and Nandu, both summer w heat varieties, were excised from 4 and 10 day-old seedlings, and used for induction of embryogenic callus. A modified L3 medium, supplement ed with 10 mu M 2,4-dichlorophenoxyacetic acid (2,4-D) for culture ini tiation, and 5 mu M 2,4-D for subculturing, was optimal; 90% of 4 day- old 'Turbo' seedlings formed embryogenic callus. Optimal plant regener ation was achieved from callus incubated on a modified MS medium witho ut 2,4-D, but supplemented with 2.22 mu M 6-benzylaminopurine and 0.27 mu M naphthaleneacetic acid. Plantlets formed via embryogenesis from ail embryogenic 'Turbo' calli initiated from 4 day-old explants, with a mean number of 8 regenerants per explant. Regeneration occured via e mbryogenesis only. Results obtained using 'Nandu' were within the same range.