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Systematics Section / ASPT

Spooner, D. M. [3], Stephenson, Sarah [3], Ballard, Harvey [1], Polgar, Zsolt [2].

DNA sequences of single-copy waxy (GBSSI) gene of diploid and polyploid wild potatoes (Solanum section Petota).

This study used DNA sequences from the single-copy nuclear gene, waxy, to investigate its utility as a phylogenetic marker for wild potatoes (Solanum sect. Petota), similar to its proven utility in the sister clade of wild tomatoes (Solanum section Lycopersicon). Potatoes, like tomatoes, contain diploids (2n = 2x = 24), but also tetraploids (2n = 4x = 48) and hexaploids (2n = 6x = 72); thirty percent of the approximately 200 wild potato species are polyploid. The allopolyploid or autopolyploid origin of different potato polyploids is conjectural. This study used waxy to test hybrid origins of presumed allopolyploid species in tetraploid Solanum series Longipedicellata (genome designation AB); hexaploid series Demissa (genome designation A1A4 (BB, or CC, or DD), or ADD (bdgs); tetraploid series Acaulia (AAa), and hexaploid series Acaulia (AAaX). Cladistic analyses of waxy sequences completely concur with prior chloroplast DNA (cpDNA) restriction site data regarding outgroup relationships. When just the diploids are analyzed, waxy is concordant with the four-clade cpDNA results except clade 1 representatives (S. clarum, S. jamesii, S. polyadenium; Mexican diploids), and clade 2 (S. bulbocastanum and S. cardiophyllum) are members of the same grade, and clade 3 (Solanum series Piurana clade) is basal. When the cloned waxy sequences from the polyploids are included in cladistic analyses, the divergent copies sometimes fall into two clades, and support a diversity of allopolyploid origins to include hybrids between members of clades 1 or 2 and clade 4 (series Longipedicellata), and of clade 3 and clade 4 (ser. Demissa). Some cloned sequences fall completely within different branches of clade 4 (ser. Acaulia ). These results suggest a diversity of autopolyploid and alloploid origins, and explain the great taxonomic difficulty in distinguishing these series, and defining species within them.

1 - Ohio University, Department of Environmental and Plant Biology, Porter Hall, Richland Avenue, Athens, Ohio, 45701-2979, USA
2 - Technical University of Cluj-Napoca, Department of Communications, 26 Baritiu Street, Cluj-Napoca, 3400, Romania
3 - USDA-ARS, University of Wisconsin, Department of Horticulture, 1575 Linden Drive, Madison, Wisconsin, 53706-1590, USA

phylogenetic inference

Presentation Type: Paper
Session: 37-12
Location: Cottonwood B (Snowbird Center)
Date: Tuesday, August 3rd, 2004
Time: 5:00 PM
Abstract ID:17

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