Nuclear and chloroplast DNAs reveal diverse origins and mis-identifications of Juniperus chinensis cultivars from Windsor Gardens, UK. Part 2 of 3
Résumé
Ploidy was determined for twenty four (24) plants labeled as Juniperus chinensis cultivars at the Windsor Gardens, UK and revealed 16 were tetraploids (2n=4x=44), 7 diploids (2n=2x=22), and one triploid (2n=3x=33). nrDNA (ITS) and cp DNA sequencing found one of the diploids was actually a cypress; J. chinensis cv Savill Sentinel was Cupressus gigantea. A second diploid, cv 'Spartan' was J. virginiana. Only three of the remaining 22 'chinensis cultivars' had both nrDNA and chloroplasts (cp) of J. chinensis: Iowa (=Globosa), Obelisk and Plumosa Aurea and these, having homozygous nrDNA, appear to be autotetraploids. Four other cultivars had J. chinensis nrDNA but cp of J. tsukusiensis. Two cultivars, Richeson and Fruitlandii, were determined to be J. xpfitzeriana. Two cultivars, Japonica and Japonica Variegata, had nrDNA and cp of J. chinensis var. sargentii. The remaining ten 'J. chinensis cultivars' had J. chinensis hybrid nrDNA. But, these 10 cultivars had 3 kinds of cp DNA: 7 had J. chinensis var. sargentii cp; 2 with J. sabina var. balkanensis cp; and one, Kek, had J. chinensis cp. The amount of hybridization among the parents of cultivars in botanic gardens makes it very difficult to identify cultivated junipers. In this sample of 24 'J. chinensis' cultivars, only 3 plants were 'pure, autotetraploid 'J. chinensis' by DNA. A DNA barcode system, if utilized, would greatly aid botanic gardens to screen current and incoming accessions to assign taxonomic names to junipers. Published on-line www.phytologia.org Phytologia 102(3): 106-115 (Sept 21, 2020).
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