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ARS Home » Northeast Area » Washington, D.C. » National Arboretum » Floral and Nursery Plants Research » Research » Publications at this Location » Publication #201619
Title: SSR Marker Analysis of Genetic Relationships within Hydrangea Macrophylla

Author
item Reed, Sandra
item Rinehart, Timothy - Tim

Submitted to: Journal of the American Society for Horticultural Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/5/2007
Publication Date: 5/15/2007
Citation: Reed, S.M. and Rinehart, T.A. 2007. SSR marker analysis of genetic relationships within Hydrangea macrophylla. J. Amer. Soc. Hort. Sci. 132:341-351.

Interpretive Summary: At least 200 cultivars of Hydrangea macrophylla, which is also known as bigleaf, garden, French and florist hydrangea, are currently available in the U.S. Some of these cultivars were bred in Europe during the first half of the last century. Others have been recently introduced from Europe and Japan, while others are of unknown origin. Many cultivars appear very similar, leading to speculation that they are genetically the same. Little is known about the parentage of most cultivars. The purpose of this study was to use molecular markers to study genetic relationship among H. macrophylla cultivars. Results of this study support the subspecies designation for serrata rather than the H. serrata epithet. The remontant, or reblooming, cultivars 'Endless Summer', 'Oak Hill', 'David Ramsey', 'Decatur Blue' and 'Penny Mac' were found to genetically very similar, but could be distinguished from each other using molecular markers. Some presumed synonyms were found to be valid ('Preziosa' and 'Pink Beauty', 'Rosalba' and 'Benigaku', 'Geoffrey Chadbund' and 'Mowe'), while others were not ('Harlequin' and 'Buttons 'n Bows', 'Nigra' and 'Mandschurica'). This study identified potentially unexploited sources of germplasm within H. macrophylla and relationships between existing cultivars of this popular shrub. This information should of value when selecting parents for breeding programs.

Technical Abstract: Genetic diversity studies using 39 SSR markers were carried out with 114 taxa of H. macrophylla. The SSR loci were highly variable among the taxa, producing a mean of 8.26 alleles per locus. Overall allelic richness was relatively high at 5.12 alleles per locus. Subspecies serrata contained nearly twice the allelic diversity of ssp. macrophylla. The majority of genetic diversity was found to reside within the subspecies, with only 12% of the total genetic diversity observed occurring between subspecies. Four cultivars that appeared to be hybrids between the two subspecies were identified. Genetic similarities were found among five remontant cultivars ('Endless Summer', 'Oak Hill', 'David Ramsey', 'Decatur Blue', 'Penny Mac') and several non-remontant cultivars, including 'General Vicomtesse de Vibraye', 'Nikko Blue', 'All Summer Beauty' and 'La France'. No close genetic relationship was found between the remontant cultivar ‘Forever and Ever’ and other remontant cultivars. Genetic similarities were found among variegated and double-flowered cultivars. Within ssp. macrophylla, cultivars with mophead inflorescences clustered separately from most lacecap cultivars. Some presumed synonyms were found to be valid ('Preziosa' and 'Pink Beauty', 'Rosalba' and 'Benigaku', 'Geoffrey Chadbund' and 'Mowe'), while others were not ('Harlequin' and 'Buttons 'n Bows', 'Nigra' and 'Mandschurica'). This study identified potentially unexploited sources of germplasm within H. macrophylla and relationships between existing cultivars of this popular shrub. This information should of value when selecting parents for breeding programs.