Total DNA Content and Ploidy Levels in Linnaeoideae with a Focus on Abelia

Abstract

The Linnaeoideae subfamily was created in Caprifoliaceae to represent the close relationship among the monophyletic genera Abelia, Diabelia, Dipelta, Kolkwitzia, Linnaea, and Vesalea. These closely related genera could possibly be a new source of ornamental traits for Abelia, an economically important genus of woody ornamental shrubs. Breeding among these genera could be challenging as only a few genera and species have a reported total DNA content, ploidy level, and chromosome number. The objective of this research was to fill that gap in the literature. We determined the total DNA content and DNA ploidy levels and estimated chromosome numbers of the species Abelia chinensis (two genotypes), Abelia macrotera var. engleriana, Abelia ×grandiflora, Abelia schumanii, Diabelia serrata, Vesalea floribunda, Zabelia tyaihyonii var. mosanensis, and the Abelia cultivars Edward Goucher, Francis Mason, Lavender Mist, Raspberry Profusion, and Rosy Charm® by flow cytometry. Raphanus sativus ‘Saxa’ was used as an internal standard for holoploid 2C total genome size estimation. For DNA ploidy and chromosome number, A. ×grandiflora (2n = 2x = 32) and Z. tyaihyonii var. mosanensis (2n = 36) were used as internal standards. We also measured the pollen size and stomata length of the species A. chinensis (two genotypes), A. macrotera var. engleriana, V. floribunda, A. ×grandiflora, A. schumanii, and D. serrata, and the Abelia cultivars Francis Mason and Raspberry Profusion. All genotypes have a 2C holoploid total DNA content between 0.87 and 0.95 pg DNA (∼850–930 Mb), except for V. floribunda and Z. tyaihyonii var. mosanensis, which have 1.94 and 1.91 pg DNA, respectively (∼1880 Mb). All genotypes are diploid with 2n = 2x = 32, except for V. floribunda and Z. tyaihyonii var. mosanensis, which have 36 chromosomes (2n = ?x = 36). We observed significant variability in stomata sizes and pollen diameter independent of and not correlated with genome size or chromosome number. A. ×grandiflora has a high percentage of dead pollen (∼30%), as does V. floribunda (43%). This high percentage of dead pollen in the natural species V. floribunda could be the result of aneuploidy. This is the first report of total DNA content in A. chinensis, D. serrata, and Z. tyaihyonii var. mosanensis; total DNA content and estimated chromosome number in V. floribunda; total DNA content and DNA ploidy levels in A. ×grandiflora, A. macrotera var. engleriana, and A. schumanii; and total DNA content, estimated chromosome number, and DNA ploidy levels in the Abelia cultivars Edward Goucher, Francis Mason, Lavender Mist, Raspberry Profusion, and Rosy Charm®.