A Flow Cytometry-Based Assessment of the Nuclear DNA Content and Ploidy Level of Wild Sunflower Species

Sunflower genus (Helianthus spp.), native to North America, includes 37 perennials and 14 annual species, many of which possess valuable genes related to biotic and abiotic stress tolerance that can enhance yield and yield-related traits in cultivated sunflower. However, it is crucial to characterize wild species to incorporate these beneficial traits into breeding programs. The study aim was to determine the nuclear DNA content of 133 sunflower accessions representing 52 species of the genus by flow cytometer and use the obtained information to determine their ploidy levels and verify their taxonomic identities. Based on flow cytometrical analysis, nuclear DNA content of the individual plants and the average values of accessions of the same species generally showed a high degree of similarity, except in some cases. However, the average 2C nuclear DNA content of Helianthus species was estimated to range from 5.61 pg (H. porteri) to 27.05 pg (H. tuberosus). The differences among the species were statistically significant. Based on the study results, it was determined that approximately 80% (41 species) of the wild species (15 annuals, 26 perennials) are diploid. The ploidy level of the remaining species exhibited variability, and 12 species were tetraploid (4x) while 2 species were hexaploid (6x). The study results indicated that some accessions of some species were either identified incorrectly or they are progenies of natural interspecific hybrids. The study's results confirm that flow cytometer can be used to characterize the sunflower genetic resources before including them in breeding programs.