title: Phylogenetic relationships of the sweetpotato in Ipomoea series Batatas (Convolvulaceae) based on nuclear beta-amylase gene sequences.
abstract: Phylogenetic relationships of 13 accessions and a cultivar representing the sweetpotato, Ipomoea batatas (L.) Lam., and its wild progenitors, were investigated using the nucleotide sequence variation of a nuclear-encoded beta-amylase gene. A 1.1-1.3 kb fragment of the gene spanning two exons separated by a long intron was PCR-amplified, cloned, and sequenced. Exon sequences proved highly conservative, while intron sequences yielded large differences. Intron analyses grouped species in a phylogenetic context according to the presence of two genome types: A and B. These groups are consistent with results of previous analyses, save for the novel placement of I. tiliacea, among the A-genome species. Sequences specific to both A and B genome species have been identified. Exon sequences indicate that I. ramosissima and I. umbraticola are quite different from other A-genome species. Placement of I. littoralis is questionable; its intron is similar to other B-genome species, but its exons are quite different. Exon evolution indicates that the B-genome has evolved faster than the A-genome. Interspecific intron and exon variation indicates I. trifida, I. tabascana, and I. batatas form a monophyletic group.
authors.affiliation: Department of Biological Sciences, Clemson University, Clemson, SC 29634, USA. rsriyan@clemson.edu
authors.forename: Sriyani
authors.initials: S
authors.lastname: Rajapakse
authors.forename: Sasanda D
authors.initials: SD
authors.lastname: Nilmalgoda
authors.forename: Matthew
authors.initials: M
authors.lastname: Molnar
authors.forename: Robert E
authors.initials: RE
authors.lastname: Ballard
authors.forename: Daniel F
authors.initials: DF
authors.lastname: Austin
authors.forename: Janice R
authors.initials: JR
authors.lastname: Bohac
mesh_terms: D002467:Cell Nucleus / Q000201:enzymology* / Q000235:genetics; D019143:Evolution, Molecular; D005091:Exons; D017343:Genes, Plant; D016678:Genome; D007438:Introns; D027723:Ipomoea batatas / Q000235:genetics*; D008957:Models, Genetic; D010802:Phylogeny; D016133:Polymerase Chain Reaction; D017422:Sequence Analysis, DNA; D001614:beta-Amylase / Q000235:genetics*
chemical_list: D001614:beta-Amylase