Two alternative pathways of somatic embryo origin from polyembryonic mature stored seeds of Pinus koraiensis Sieb et Zucc.

Individual mature stored seeds of Pinus koraiensis sometimes contain several viable zygotic embryos originated through the processes of simple and cleavage polyembryony. To induce the embryonic process, isolated zygotic embryos were cultured on five different media all supplemented with 10 mu M 2,4-dichlorophenoxyacetic acid and 5 mu M 6-benzyladenine. Two alternative pathways of somatic embryo origin were revealed. The first pathway was associated with the production of a friable, translucent callus in the hypocotyl-cotyledon region of the dominant zygotic embryo. The second pathway was related to the proliferation of a translucent, moist, and mucilaginous tissue (termed embryonal-suspensor mass) in the suspensor region of the dominant zygotic embryo. Both types of tissues contained early somatic embryos. Regression analysis has shown a strong negative correlation between the frequencies of formation of embryogenic callus and embryonal-suspensor mass both at 3 and 8 weeks of culture (r = -0.85; p = 0.07 and r = -0.71; p = 0.17, respectively).