PLOIDY LEVEL AND GENOME SIZE OF SEVERAL DIOSPYROS SPECIES

Callus cells induced from leaf primordia were used for a rapid and eff icient determination of genome size and ploidy level of several Diospy ros spp, including D. kaki. Nuclear DNA contents of nine Japanese pers immon (Diospyros kaki Thunb.) cultivars and other 12 Diospyros species were estimated by flow cytometry. Compared to the known nuclear DNA c ontents of chicken red blood cells and tobacco leaf cells, genome size s of hexaploid cultivars (2n = 6x. x = 15) of D. kaki were estimated t o 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 l inear correlation between the ploidy levels and the genome sizes of Di ospyros spp, tested, except for D. montana. In this study, chromosome number was also counted, using callus cells to determine if ploidy lev els 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 tetrapl oid with 2n=60, and the other species tested, including four species w hose ploidy levels had been unknown, were determined to be diploid. Th e results agreed with the deduced ploidy levels from flow cytometry ex cept for D. montana.