Sriyani Rajapakse

Phylogenetic relationships of the sweetpotato in Ipomoea series Batatas (Convolvulaceae) based on nuclear β-amylase gene sequences

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.

Identification of rose cultivars by restriction fragment length polymorphism

Abstract Restriction fragment length polymorphisms (RFLP) were investigated as a means of identifying rose ( Rosa × hybrida) cultivars for patent protection. A library of genomic DNA was generated by shotgun cloning HindIII digested DNA fragments of the rose cultivar ‘Confection’ into the plasmid pUC8. Clones with low copy number sequences were identified and used as probes in Southern hybridization analyses of restriction digested DNA from different rose cultivars. We have identified 15 probes that display RFLP useful in cultivar identification. One of these probes, pH1.3C, can identify 12 different cultivars. Based on hybridizations with probes pH1.3C and pH1.6C, a total of 16 cultivars have been distinguished from one another. Using different restriction enzyme and probe combinations, we expect to distinguish many more rose cultivars.