Ploidy levels of 61 Actinidia accessions representing seven species and three interspecific crosses currently available in the United States were determined by flow cytometry. Accessions representing relatively cold-hardy germplasm were emphasized. One plant from each ploidy level was examined microscopically to confirm the flow cytometry ploidy estimate. There were 17 diploids, 40 tetraploids, and four hexaploids. All A. kolomikta and A. polygama accessions were diploid. All accessions of A. arguta (vars. arguta and purpurea), A. callosa and A. melanandra were tetraploid. An open-pollinated seedling of the A. deliciosa cultivar 'Hayward' was hexaploid. One accession of A. chinensis, Orange BOR 0919, was tetraploid. Two hexaploid accessions, DACT 0021.14 and DACT 0021.3, received as A. chinensis, are suspected to be A. deliciosa based on morphology and ploidy level. The A. arguta x A. polygama cross, 'Issai', was hexaploid and the A. arguta x A. melanandra crosses, 'Ken's Red' and 'Red Princess', were tetraploid. Because crossing success and hybrid fertility in Actinidia can be hindered by inter- or intraspecific ploidy differences between parents, the determination of the ploidy levels of these accessions should facilitate systematic breeding.
- Nuclear DNA content