Testing the Utility of Intergenic Spacer Regions to Identify Distinct Plumeria Taxa

In Hawaii, plumeria cultivars contribute to the floriculture, landscape, and tourist industries. However, many of the cultivars suffer from insect, fungal, and viral afflictions, thereby diminishing flower yields and rendering plants unmarketable or unfit for export. A plumeria breeding program will help to overcome these problems, while simultaneously creating novel plumeria cultivars. Information about genetic relationships from molecular studies can allow us to develop better breeding strategies to introduce horticulturally important traits from Plumeria spp. into cultivated Plumeria. Recent studies have employed the use of intergenic spacer (IGS) regions to distinguish species and assess genetic similarity. In this preliminary experiment, five morphologically distinct Plumeria species were chosen to test the utility of six IGS regions for separating putative Plumeria species. Molecular data sets for IGS regions—trnQ-rps16, ndhF-rpl32, psbD-trnT, psbJ-petA, rpl32-trnL, and trnV-ndhC—were analyzed separately and in combination by means of Neighbor-Joining (NJ) and Maximum Parsimony (MP) methods to test for congruence. Intergenic regions psbD-trnT and trnQ-rps16 were the most successful single regions at identifying genetic relatedness among Plumeria spp., while recovering outgroup taxa. Both regions yielded similar tree topologies between NJ and MP analyses. The combination of these two regions yielded similar tree topologies to trees generated from analyses of individual regions, but with higher branch support. In conclusion, these two regions can now be used to further assess the genetic relatedness among Plumeria spp. and cultivars to develop better breeding strategies.