ARS | Publication request: GBSSI (WAXY) GENE PHYLOGENY OF WILD POTATOES (SOLANUM SECTION PETOTA)

Submitted to: Botanical Society of America Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: June 15, 2004
Publication Date: July 15, 2004
Citation: Spooner, D.M., Stephenson, S.A., Ballard, H., Polgar, Z. 2004. Gbssi (waxy) gene phylogeny of wild potatoes (solanum section petota). 2004 Botanical Society of America Abstracts. p. 62.

Technical Abstract: 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.