2018 ASHS Annual Conference

Asclepias is an important ecologic host and food source for many butterfly species that utilize nectar and foliage as a food source. It is also known for its attractive floral structures and performance in landscape environments with minimal fertilizer and irrigation inputs. Despite having ornamentally and ecologically valuable traits, cultivars of Asclepias spp. are not commonly found in the ornamental market as Asclepias spp. does not tolerate commercial growing protocols that incorporate high fertility and irrigation rates, and as a result grow to heights too large for efficient racking and shipping or suffer from pathogens. Another major challenge in developing hybrid cultivars is that hybrid fertilized embryos often undergo late-term abortion. This has deterred many ornamental breeding programs from attempting interspecific crosses within the genus. In this project, Asclepias tuberosa was used as the female parent, as this species is the most widely-grown taxa and possessed many traits superior to other species in the genus. The pollen donors were Asclepias speciosa, A. syriaca, A. viridis, A. incarnata, A. purpurascens, A. hirtella, and A. fascicularis. Each of the species used as pollen parents was selected to introgress beneficial traits that could improve yield commercially viable cultivars. For example, A. incarnata and A. hirtella thrive under wet soil conditions, similar to production environments and irrigated landscapes. A. fascicularis, A. incarnata, and A. viridis have naturally occurring branching, another trait valuable to the industry. A. viridis, A. purpurascens and A. fascicularis are diminutive in height, differing drastically from most species that range from 1.2 to 1.8 meters. Flower color of species used in this study is far different than A. tuberosa, ranging from white to green to pinks and purples, all of which could result in broadening the floral color palette of hybrids. To overcome late term abortion, embryo rescue protocols were established and used to increase the success rates of interspecific crosses that would normally undergo late-term abortion. Embryo rescue has not been attempted before and based upon parental selection could lead to Asclepias hybrids that have enhanced production/landscape tolerances and ornamental values. This would include shorter stature, better branching, improved floral display, and tolerance to consistently moist soils (and associated pathogen pressure). All information from this study will be used to establish working protocols for embryo rescue and vegetative propagation through tissue culture, stem cutting, and root cuttings. This information will provide the industry an avenue to increase production and distribution of Asclepias to the market.