Germination, Genetic Variation, and Phylogenetic Relationships Within and Among Populations of Echinacea Augustifolia

Echinacea angustifolia DC., the common coneflower of the western Great Plains, is difficult to propagate by achenes due to inherent seed dormancy. The effects of light and prechilling on seed germination were examined, alone and in combination with scarification (mechanical, acid) and ethylene (ethephon) treatments. The results showed that a two-week-prechill treatment in combination with ethephon and continuous light, followed by a two-week-germination period in light (16 hours per day) at 25°C, could induce over 95% seed germination in E. angustifolia. This was a significantly higher percentage of germination, over a shorter period of time than any other method examined, or previously described. This treatment also synchronized germination, with a majority of the viable seeds germinating in less than one week after being placed at 25°C in the light. This study also demonstrated the usefulness of nuclear DNA Restriction Fragment Length Polymorphism (RFLPs) in detecting genetic variation within populations and determining the distribution of the genetic variation among populations (population phylogeny) of Echinacea angustifolia. Collections of Echinacea from five different populations were assayed for RFLPs, with fifty cDNA probes. All probes were polymorphic. Genetic diversity values ranged from 0. 74 in the Kansas population to 0.87 in the Wyoming population. Inter-populational genetic diversity and phylogenetic analyses suggested monophyletic origins for Wyoming & South Dakota, and Nebraska & Kansas clusters (groups). Genetic similarity decreased as the geographical distance between populations increased. Although tetraploidy in Echinacea angustifolia has been reported, chromosome counts of random samples from North Dakota and South Dakota populations showed no sign of polyploidy