Endosperm response to pollen irradiation in kiwifruit

Cytological details of endosperm development after pollination with irradia ted pollen were studied in Actinidia deliciosa (kiwifruit) cultivar Hayward . Pollinations were carried out involving five different sources of pollen (Matua, Tomuri, Burt, Berryman, and fruiting male) irradiated with gamma ra ys at doses of 700 and 900 Gy. Non-irradiated crosses were used as controls . Irradiated pollen induced development of approximately 25-30% of the ovul es. Two types of ovules were observed: (1) with both embryo and endosperm a nd (2) with endosperm only. No mitotic abnormalities were found in control or irradiated endosperms. Mitotic divisions were regular and nuclei spheric al and evenly spaced. However, the cells of irradiated endosperm usually co ntained low amounts of storage products. Ploidy level of the endosperms was evaluated by nuclear size (volume) with the use of image analyzis. Mean nu clear size in control and irradiated endosperms was 1598.3 and 750.9 mu m(3 ), respectively. It is concluded that endosperm produced after pollination with irradiated pollen is autonomous and represents the 2n level.