Friend, Sheena A. , Quandt, D. , Hilu, Khidir W. .
Species, genomes and section relationships in genus Arachis (Fabaceae): a molecular phylogeny.
The South American genus Arachis L. (Fabaceae) contains 80 species, including cultivated peanut (A. hypogaea L.). Krapovicaks and Gregory (1994) divided Arachis into nine sections based on morphology, geographic distribution and cytogenetics: Arachis,Caulorrhizae, Erectoides, Extranervosae, Heteranthae, Procumbentes, Rhizomatosae, Trierectoides, and Triseminatae. Despite its economic importance, a comprehensive phylogeny for the genus does not exist. We have used here sequence information from plastid trnT-trnF and nuclear ITS from a total of 47 species representing all nine sections to reconstruct the first molecular phylogeny for the entire genus. Chapmannia and Stylosanthes were used as outgroup. Our results show that apart from the monotypic Triseminatae and the well circumscribed Caulorrhizae, almost none of the formerly recognized sections form monophyla. Most strikingly, we identified A. macedoi (section Extranervosae) as being the first branching lineage, whereas the remaining species of the section are resolved elsewhere. Arachis macedoi is followed by a grade of three lineages representing section Triseminatae, section Caulorrhizae, and sections Heteranthae + Trierectoides plus the majority of Procumbentes as well as A. paraguariensis, and a large terminal clade mainly consisting of section Arachis. Within section Arachis two major clades, Arachis I & II were identified. Whereas, Arachis I contains a mixture of representatives from Arachis, Erectoides, Extranervosae, and Procumbentes, Arachis II is more homogeneous including exclusively representatives from Arachis plus A. glabrata (Rhizomatose). This is in sharp contrast with Krapovicaks and Gregory’s predictions. In addition, the combination of plastid and nuclear sequences provided useful information on species and genome relationship in section Arachis. The allotetraploid species showed two ITS alleles derived from respective parents, which in combination with chloroplast data provided further insight into genome evolution of the tetraploids. Moreover, several chimeric ITS1 & 2 copies were detected. We also report the first CBC in the P8 of the trnL intron.
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1 - Virginia Tech, Department of Biological Sciences, 2119 Derring Hall
, Blacksburg, VA, 24061-0406, United States
2 - Rheinische Friedrich-Wilhelms-Universität, Nees-Institut für Biodiversität der Pflanzen, Meckenheimer Allee 170, D-53115, Bonn, Germany
3 - Virginia Tech, Biological Sciences, Blacksburg, Virginia, 24061, USA
Presentation Type: Oral Paper:Papers for BSA Sections
Location: Maybird/Cliff Lodge - Level C
Date: Monday, July 27th, 2009
Time: 10:15 AM