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Abstract Detail


Economic Botany: Evolution of Cultivated Plants

Renner, Susanne S [1], Schaefer, Hanno [1], Kocyan, Alexander [1].

Phylogenetics of Cucumis (Cucurbitaceae): C. sativus (cucumber) belongs in an Asian/Australian clade far from C. melo (melon).

Cucumis, as traditionally conceived, is geographically centered in Africa, with C. sativus and C. hystrix thought to be the only Cucumis species in Asia. This taxonomy forms the basis for all ongoing Cucumis breeding and genomics efforts. We tested relationships among Cucumis and related genera based on DNA sequences from chloroplast gene, intron, and spacer regions (rbcL, matK, rpl20-rps12, trnL, and trnL-F), adding nuclear internal transcribed spacer sequences to resolve relationships within Cucumis. Analyses of combined chloroplast sequences (4,375 aligned nucleotides) for 123 of the 130 genera of Cucurbitaceae indicate that the genera Cucumella, Dicaelospermum, Mukia, Myrmecosicyos, and Oreosyce are embedded within Cucumis (Kocyan et al., MPE in press). Phylogenetic trees from nuclear sequences for these taxa are congruent, and the combined data yield a well-supported phylogeny (BMC Evol. Biol., see link). The nesting of these genera in Cucumis extends the natural geographic range of the genus throughout the Malesian region and into Australia. The closest relative of Cucumis is Muellerargia, with one species in Australia and Indonesia, the other in Madagascar. Cucumber and its sister species, C. hystrix, are nested among Australian, Malaysian, and Western Indian species, with the Australian species not yet formally described. Surprisingly, C. melo is sister to this Australian/Asian group, rather than being close to African species as previously thought. Molecular clocks indicate that the deepest divergences in Cucumis, including the split between C. melo and its Australian/Asian sister clade, go back to the mid-Eocene, while the split btw. C. sativus and C. hystrix is c. 8 my old. With the new phylogeny it should be possible to infer the genome rearrangements that led to the 7 chromosomes of C. sativus (while C. hystrix has n = 12) via analyses of co-linearity between these two species and their closest relatives.


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Related Links:
BMC Evol. Biol. paper on Cucumis phylogeny


1 - University of Munich, Organismal Biology, Menzingerstr. 67, Munich, 80638, Germany

Keywords:
Cucumis
Biogeography
phylogenetics
crop wild relatives
Economic plants
nuclear and chloroplast DNA analysis.

Presentation Type: Poster:Posters for Topics
Session: P
Location: Exhibit Hall (Northeast, Southwest & Southeast)/Hilton
Date: Sunday, July 8th, 2007
Time: 8:00 AM
Number: P68001
Abstract ID:2030


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