Selection of New Pollinizer Variety ‘Nijitaro’ for ‘Rainbow Red’ Kiwifruit and Development of Techniques for Its Use

Abstract

Synchronization of the flowering period between male and female varieties is fundamental in kiwifruit cultivation without artificial pollination. The flowering period of the red-fleshed kiwifruit ‘Rainbow Red’ occurs earlier than that of conventional male varieties. We selected ‘Nijitaro’ as a pollinizer, a new male variety from the chance seedlings of ‘Rainbow Red’. The blooming stage of ‘Nijitaro’ nearly matched that of ‘Rainbow Red’ and its pollen fertility was similar to that of other conventional male varieties. The number of anthers and amount of pure pollen this variety produces were smaller than those of hexaploid varieties such as ‘Tomuri’. On the basis of the results of flow cytometry analysis and the rate of fertile seed development, this variety is a diploid type of Actinidia. Partial cane grafting of ‘Nijitaro’ on ‘Rainbow Red’ achieved a higher bearing rate than that of independent male trees distributed in the open pollination test field. Especially, ‘Nijitaro’ cane was present within a circle of 2 m, with both bearing and fruit enlargement suitably secured. Thus, the ‘Nijitaro’ variety is an unsuitable pollinizer for artificial pollination, but it is effective for open pollination of cultivated ‘Rainbow Red’.