|Trueblood, Clara - North Carolina State University|
|Ranney, Thomas - North Carolina State University|
|Lynch, Nathan - North Carolina State University|
|Neal, Joseph - North Carolina State University|
Submitted to: HortScience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/2/2010
Publication Date: 8/1/2010
Citation: Trueblood, C.E., Ranney, T.G., Lynch, N.P., Neal, J.C., Olsen, R.T. 2010. Evaluating fertility of triploid clones of hypericum androsaemum L. for use as non-invasive landscape plants. HortScience. 45:1026-1028.
Interpretive Summary: Invasive ornamental plants are a growing problem for managed landscapes, natural habitats, and the nursery industry. The development of non-invasive forms of ornamental plants is a viable option to increase sustainability of cultivated landscapes. Triploid, ornamental forms of Hypericum androsaemum were evaluated for both male and female fertility in controlled pollinations and natural conditions. The reduction in fertility varied among different triploid clones; however, all showed significant reductions in pollen viability. Nine out of ten triploids produced no viable seed, with one plant producing two seedlings that soon died. This research documented high levels of male infertility and no measureable female fertility among triploid hypericum. This will facilitate the introduction of infertile hypericum clones to the nursery industry for mitigating concerns over invasiveness.
Technical Abstract: Hypericum androsaemum is a valuable landscape plant that is potentially invasive in certain parts of the U.S. Infertile, non-invasive, cultivars of H. androsaemum with desirable ornamental features would be ecologically beneficial and valuable for the horticultural industry. Male and female fertility of ten triploid H. androsaemum, developed with a combination of variegations and foliage colors, was investigated under greenhouse (controlled pollinations) and field conditions (natural pollination). Male fertility was evaluated based on pollen viability tests (pollen staining and pollen germination). Female fertility was based on fruit set, seed set, germination capacity of seeds, and number of seedlings produced for each flower. Values for different measures of fertility varied among triploid clones; pollen germination was significantly reduced for all triploids and nine of the ten triploids produced no viable seed representing 100% failure of approximately 171,000 potential fertilization events (based on fertility levels of diploid controls). The remaining triploid clone produced 2 seedlings per flower (compared with 260 for the controls), but those seedlings died shortly after germination. This research documented that these triploid H. androsaemum are highly infertile with no measurable female fertility. These clones will provide ideal alternatives to fertile forms of H. androsaemum where naturalization is a concern. These methods also provide a rigorous protocol for evaluating fertility of other taxa that are selected or developed as non-invasive cultivars of potentially weedy species.