Location: Floral and Nursery Plants ResearchTitle: Molecular verification of Osmanthus armatus hybrids
|WU, XINGBO - Orise Fellow|
|HASSLER, SAMUEL - Tennessee State University|
Submitted to: Southern Nursery Association Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 4/8/2020
Publication Date: 7/1/2020
Citation: Alexander, L.W., Wu, X., Hassler, S. 2020. Molecular verification of Osmanthus armatus hybrids. Southern Nursery Association Proceedings. 64/74:84.
Interpretive Summary: Production and use of Osmanthus as a landscape plant is currently limited to USDA Hardiness Zones 7 – 10, and nursery growers wish to extend the range of Osmanthus species into colder climates. In an effort to improve cold-hardiness in Osmanthus, controlled and open-pollinated crosses were made using cultivars of the cold-hardy species Osmanthus armatus. A panel of eight SSR markers was used to confirm the parentage of controlled crosses and determine parentage of open-pollinated crosses. All controlled crosses of O. armatus ‘Longwood’ x O. heterophyllus ‘Rotundifolius’ were confirmed. Open-pollinated crosses of O. armatus ‘Longwood’ and O. armatus ‘Jim Porter’ were assigned parentage with high probability. All parents had unique identities based on eight microsatellite markers. This is the first report of O. armatus x O. heterophyllus, O. armatus x O. x fortunei, and O. armatus x O. fragrans hybrids.
Technical Abstract: Production and landscape use is currently limited to USDA hardiness zones 7 – 8 for sweet olive, zones 7 – 9 for holly tea olive, and zones 7 – 10 for fragrant tea olive. A recent field evaluation of Osmanthus in Tennessee showed large variation in cold tolerance among species and cultivars that could be exploited in a hybrid breeding program. The objective of this study was to make controlled and open-pollinated crosses among Osmanthus species and verify parentage of hybrids using molecular markers. Controlled crosses of Osmanthus armatus ‘Longwood’ and open-pollinated crosses of O. armatus ‘Jim Porter’ were made October 2016, collected February 2017, and germinated April – December 2017. DNA was isolated from leaf tissue of 72 putative hybrids and 24 candidate parents in June 2018. Previously tested SSR loci were amplified and sized via genotyping. Cervus 3.0.7 was used to calculate allele frequencies and assign parentage. All controlled crosses of O. armatus ‘Longwood’ x O. heterophyllus ‘Rotundifolius’ were confirmed. Male parents of open-pollinated O. armatus ‘Longwood’ included the O. heterophyllus cultivars Rotundifolius and Ogon. Male parents of open-pollinated O. armatus ‘Jim Porter’ included O. xfortunei, the O. heterophyllus cultivars Ogon, Rotundifolius, and Variegatus, O. armatus ‘Longwood’, and O. fragrans ‘Fudingzhu’. This is the first report of hybrids between O. armatus and other Osmanthus species. Evaluation of more Osmanthus accessions and subsequent hybridizations will be necessary to introgress favorable genes and generate the variation necessary to expand the genus into new markets.