MICROSPORE EMBRYOGENESIS IN ANTHER CULTURE OF 3 SPECIES OF POPULUS AND REGENERATION OF DIHAPLOID PLANTS OF POPULUS-TRICHOCARPA

Microspore embryogenesis was induced from in vitro cultured anthers of Populus balsamifera L., Populus maximowiczii A. Henry, and Populus trichocarpa Torr. & Gray. Embryoids were formed at low frequencies on a modified Murashige and Skoog's medium, supplemented with 5 muM 6-benzylaminopurine, 5.1 mM L-glutamine, and 6% maltose. Growth regulator combinations (0-10 muM 6-benzylaminopurine and naphthaleneacetic acid) affected embryogenesis only slightly but formation of nonembryogenic callus from the anthers increased with increasing concentration of naphthaleneacetic acid. One donor clone of P. trichocarpa produced 54 embryoids from as many anthers during the two years of study. Adventitious shoots were obtained from 31 of these embryoids on woody plant medium with 2.5 muM 6-benzylaminopurine and 0.005 muM naphthaleneacetic acid. Adventitious shoots from 25 different embryoids were successfully rooted on woody plant medium containing 0.25 muM indole-3-butyric acid and transplanted to soil. Isozyme analysis confirmed microspore origin of all plants studied, and chromosome counts revealed that most of them had doubled their chromosome number spontaneously.