Ploidy Level and Genome Size of Several Diospyros Species.

Abstract

Callus cells induced from leaf primordia were used for a rapid and efficient determination of genome size and ploidy level of several Diospyros spp. including D. kaki. Nuclear DNA contents of nine Japanese persimmon (Diospyros kaki Thunb.) cultivars and other 12 Diospyros species were estimated by flow cytometry. Compared to the known nuclear DNA contents of chicken red blood cells and tobacco leaf cells, genome sizes of hexaploid cultivars (2n=6x, x=15) of D. kaki were estimated to be 5.00-5.24 pg/2C and those of nonaploid (2n=9x) to be 7.51-8.12 pg/2C. Nuclear DNA content of another hexaploid species, D. virginiana, was 5.12 pg/2C and that of a tetraploid, D. rhombifolia, was 3.76 pg/2C. Nuclear DNA contents of all the diploid species tested, except for D. montana, fell in the range of 1.57-2.31 pg/2C. Although D. montana is a diploid, its genome size was 3.48 pg/2C and about the same size as that of a tetraploid, D. rhombifolia. There was a strong positive linear correlation between the ploidy levels and the genome sizes of Diospyros spp. tested, except for D. montana. In this study, chromosome number was also counted, using callus cells to determine if ploidy levels can be deduced from flow cytometry. D. kaki cv. Miyazakitanenashi was nonaploid with chromosome number of 2n=135, D. kaki cv. Jiro and D. virginiana were hexaploid with 2n=90, and D. rhombifolia was tetraploid with 2n=60, and the other species tested, including four species whose ploidy levels had been unknown, were determined to be diploid. The results agreed with the deduced ploidy levels from flow cytometry except for D. montana.