Genetic diversity of Croatian Dalmatian pyrethrum as revealed by newly developed genomic SSRs

Dalmatian pyrethrum (Tanacetum cinerariifolium (Trevis.) Sch. Bip.) is an endemic species of the eastern Adriatic from the family Asteraceae. The plant produces pyrethrin, a secondary metabolite that has been shown to an effective natural insecticide with little or no adverse effects on humans. To assess genetic diversity, samples were collected from 10 natural populations of Dalmatian pyrethrum along the Adriatic coast and on the islands representing the species' range in Croatia. Genetic diversity analysis was carried out using 12 newly developed microsatellite markers. A total of 121 alleles with an average of 10.08 alleles per locus were detected in the studied populations, indicating high genetic diversity. Allelic richness (Nar) varied from 2.86 (Biokovo) to 5.02 (Zlarin). A total of 36 private alleles were observed in 10 populations with the highest number observed in Konavle (7). Evidence of bottlenecks was found only in the Biokovo population. Analysis of molecular variance showed that most of the genetic diversity can be explained by differences between individuals within populations (87.03%). Bayesian analysis of population structure revealed the existence of two gene pools, the mainland gene pool and the island gene pool. At K = 3, the Biokovo population formed a separate gene pool. Spatial analysis revealed that only a small proportion of genetic differentiation was due to isolation by distance (0.7%), while 40.6% of genetic differentiation was due to isolation by environmental distance. The results of this research will contribute to the development of future breeding programmes and hopefully commercial varieties of T. cinerariifolium to revive Dalmatian pyrethrum production in Croatia and the region. Furthermore, these results will help to improve conservation strategies for the species.