In Vitro Induction Of Autotetraploid Actinidia Plants And Their Field Evaluation For Crop Improvement

Autotetraploid plants of Actinidia chinensis 'Hort16A', a diploid, 2n=58, were regenerated from colchicine-treated cultures derived from both leaf discs and petioles of fruiting diploid vines. Ploidy levels in the regenerated plants were determined by flow cytometry. Seventy-seven autotetraploid plants were evaluated under field conditions, and compared with known diploid plants. Flow cytometry showed no change in ploidy over four years in the autotetraploids. Autotetraploid plants had thicker leaves and flatter flowers and could be grouped into two main groups on fruit characteristics. One type had large fruit, 160-180 g, with occasional fruit up to 250 g: their fruit were similar morphologically to fruit of the original diploid 'Hort16A', which had fruit averaging 90-120 g. The other type of autotetraploid fruit was fasciated and smaller (90-120 g). Within each group of autotetraploid fruit, there was also variation in fruit characteristics. A large number of autotetraploids may have to be raised for selection of desirable plant types.