Early Seed Development in Wheat×Rye Crosses Following Pollination with Irradiated Rye Pollen

Abstract

Early seed development was studied in wheat×rye crosses, in which irradiated (0-50 Gy) rye pollen was used for pollination. The number of cells and nuclei in the embryos and endosperms were scored daily for 6 and 3 days after pollination (DAP), respectively. Embryo and endosperm growth rates in the 2 Gy treatment were similar to the control (no irradiation). In other treatments, pollen irradiation greatly reduced the growth rates in both the tissues. The 2 Gy and control ovules had 7 to 10 times more embryo cells and 2 to 3 times more endosperm nuclei than the other treatments at 6 and 3 DAP, respectively. Several abnormalities were observed in the developing ovules of pistils pollinated with irradiated pollen. Degeneration of the endosperm began 3 DAP in the 5 Gy and higher radiation treatments but later in the 2 Gy treatment. Embryo abortion also occurred at a later stage in the 2 Gy treatment than in the higher radiation treatments. These studies indicate that gamma radiation doses beyond 2 Gy are quite deleterious to the developing ovule and in most cases the embryo sac succumbs to higher radiation treatments.