The systematic value of nuclear genome size for “all” species of Tulipa L. (Liliaceae)

Abstract

Nuclear genome size, as measured by flow cytometry with propidium iodide, was used to investigate the relationships within the genus Tulipa L. (Liliaceae). More than 400 accessions representing 123 taxa from mainly wild-collected plants were investigated. Most species of Tulipa have the same basic chromosome number, 2n = 2x = 24. However, the somatic DNA 2C value (2C) is shown to range from 32 to 69 pg for the diploids. The largest genome contains roughly 3.4 9 10 10 more base pairs than the smallest and has chromosomes that are more than twice as large. These large differences in the amount of nuclear DNA predict that the hybrids, if any arise, are usually sterile. Depending on the size of the total genome, 1 pg amounts to several thousand genes. Moreover, genome sizes are evaluated here in combination with available morphological, geographical, and molecular data. Therefore, the taxonomy proposed here is not a single-character taxonomy based on genome size alone. The genus Tulipa, as here determined, has 87 species, 29 more than accepted by van Raamsdonk et al. [Acta Hort (ISHS) 430:821-828, 1997], but including 25 species that were not available to them. Of these 87 species, 28 were not seen by Hall (The genus Tulipa, The Royal Horticultural Society, London, 1940) in a living state and placed by him in an addendum.Species of the subgenus Clusianae (Baker) Zonn. differ strongly in nuclear DNA content (DNA 2C value), 32 versus 40-68 pg for all other tulips, and are placed here in a separate subgenus. Also Orithyia, the only group with a style and with only 38-39 pg is placed in a separate subgenus. Therefore, all tulips are attributed to four subgenera, Clusianae (Baker) Zonn., Tulipa, Eriostemones Raamsd., and Orithyia (D. Don) Baker and divided further into 12 sections. Seven of the eight series of section Eichleres (A.D. Hall) Raamsd. are now placed in four sections: (1) section Lanatae (Raamsd.) Zonn., mainly confined to species from the Pamir-Alay and including series Lanatae Raamsd., (2) section Multiflorae (Raamsd.) Zonn. (including series Glabrae Raamsd.), (3) section Vinistriatae (Raamsd.) Zonn. (including series Undulatae Raamsd.), and (4) section Spiranthera Vved. ex Zonn. and Veldk. Triploids, tetraploids, and pentaploids were found in several species. DNA content confirmed the close relationships of the species within the different sections. The rather similar looking and therefore often confused T. armena Boiss.

Genome sizes of Eucomis L’Hér. (Hyacinthaceae) and a description of the new species Eucomis grimshawii G.D.Duncan & Zonneveld

“…Primitive angiosperms are now supposed to have had small genomes; increases up to a factor of 1,000 have occurred independently in various modern taxa (Leitch et al 1998). Flow cytometry was successfully used to measure the 2C-value for the genera Hosta Tratt., Helleborus L., Clivia Lindl., Nerine Herb., Agapanthus L'Hér., Galanthus L., Narcissus L., Gasteria Duval., Tulipa L., etc., by Zonneveld ( , 2008Zonneveld ( , 2009), Zonneveld and Van Iren (2001), Duncan (2003, 2006), Zonneveld and Van Jaarsveld (2005) and . In this paper it is shown that genome size alone is not sufficient to discriminate all species of Eucomis.…”

Tulipa kolbintsevii Zonn., a new species from Eastern Kazakhstan

“…The genus Tulipa L. (Liliaceae) has at least 87 species (Zonneveld 2009). These are divided in four subgenera, Tulipa, Clusianae (Baker) Zonn., Eriostemones (Boiss.)…”

“…These are divided in four subgenera, Tulipa, Clusianae (Baker) Zonn., Eriostemones (Boiss.) van Raamsd., and Orithyia (D. Don) Baker, and twelve sections (Zonneveld 2009). Genome size and the presence of nearly complete crossing barriers between the sections (Van Raamsdonk 1992;Van Raamsdonk and De Vries 1995) confirmed the close relationships of the species within the different sections.…”

“…Most species have the same basic chromosome number, 2n = 2x = 24. However, the somatic DNA 2C value is shown to range from 32 to 69 picogram for the diploids (Zonneveld 2009). They are popular spring-flowering garden plants, millions of bulbs are sold annually and over 5000 cultivars have been registered (Van Scheepen 1996).…”

“…The main reason is that many character states are polythetic-there is hardly any that is not variable even within a species, only combinations define them: flowering time, the absence or presence and type of hairs on the inside of the bulb tunic, leaf/stem hairiness, flower colour, the absence or presence of a black blotch at the base of the tepals with or without a yellow edge, and whether hairs are present at the base of the filaments. In a previous study DNA 2C value (nuclear DNA content) was used for analysis of more than 400 different accessions representing nearly all recognized species (Zonneveld 2009).…”