1976 Volume 45 Issue 3 Pages 225-230
1. The present paper deals with the preliminary efforts to produce seedless fruits in Hyuganatsu and Hassaku using crosses of 2X×4X, a procedure which results in the formation of abortive seeds in many cases.
2. Two hundred flowers of Hyuganatsu (Citrus tamurana Hort. ex TANAKA) were emasculated and pollinated with pollen grains of the 4X Natsudaidai (Citrus natsudaidai HAYATA). The fruits thus obtained were normal in size, weight and skin color, but almost all the seeds degenerated into rudiments and traces at an early stage of development. They were virtually seedless.
3. The soluble solid and titrable acid contents in the juice of the ripe seedless fruits showed no difference from the control. The edible portion of these fruits increased by 15% as compared with the control.
4. The seedless fruits did not differ from the controls by date of dropping early or late. Also they displayed similar pattern of development of dry juice sacs after freezing in the winter. The fruits after harvest were stored in a carton box under room condition for about two months. They did not display any particular change in the contents of the soluble solids and titrable acids in the juice during storage. The seedless fruits seemed to soften a little faster than that of the control fruits.
5. The flowers of the Hassaku (Citrus hassaku HAYATA) were pollinated with pollen grains of the 4X Natsudaidai. The fruits thus obtained were virtually seedless and did not differ from the control in fruit growth and size or in other qualities. The results coincided with those for the Hyuganatsu×4X Natsudaidai cross.
6. Further investigations are under way for the purpose of finding the proper proportion of the 4X Natsudaidai tree to be planted as a pollinizer for Hyuganatsu.
