Early seed development in hexaploid triticale

Abstract

The development of the embryo, endosperm, and antipodals was studied in five hexaploid triticale lines. The egg cell was fertilized 10–15 h after pollination. The first division of the zygote occurred 15–20 h later. Ninety-six hours after pollination there was a twofold difference among the lines in the number of embryo cells, which ranged from 17 to 31. The polar nuclei were fertilized 4–5 h after pollination and the first division of the primary endosperm nucleus took place 2–3 h later. At 60 h the lines examined fell into two groups with respect to endosperm development: one group included 6A190 and 6A250, both raw amphiploids, which had 1032 and 486 endosperm nuclei, respectively; and another which included Rosner, Armadillo 458, and 6517, all products of artificial selection, with 209, 201, and 98 endosperm nuclei, respectively. The first five or six endosperm divisions were highly synchronized while later a gradient was established. Cellularization of endosperm was first observed 96 h after pollination. No appreciable amount of mitotic abnormalities was observed in the endosperm nuclei. In all lines examined endosperm nuclei were found with DNA amount exceeding 6C.The number of antipodals, some of which were highly endopolyploid (up to 256C), ranged from 10 to 30 within and among lines. Disintegration of the antipodals began about 3 days after pollination in 6A190, at 4 days in Rosner, and at 5 days in the other lines. The rate of endosperm development and especially the disintegration of the antipodal complement seemed to be positively related with the amount of seed shrivelling observed in the lines studied.