Assessing Genetic Relationship Among Scented Geraniums (Pelargonium sp.) with TRAP Markers

Scented geraniums (Pelargonium sp.) are a group of attractive plants known for various growth habits, foliage colors, and aromatic scents.  Recent reports and patents on their capabilities for heavy metal hyperaccumulation and insect deterrence have attracted attention and added new avenues for using these plants.  Since the scented geraniums are comprised primarily of hybrids, the use of morphological characteristics is limited and often causes confusion in the identification of plants in this group. The utilizing GC/MS to analyze volatile compounds attributing to the scents of scented geraniums revealed distinct chemical profiles useful in grouping geraniums into distinctive chemotypes.  In addition, morphological or chemical attributes rarely reveal genetic relationships among the plants under investigation.  To overcome the difficulty in plant identification and genetic relationship assessment in scented geranium, we are employing DNA marker techniques in conjunction with morphological observation and chemical analysis.  In this experiment, 96 scented geraniums were observed for morphological traits (flower color, leaf size and shape, and growth habit), analyzed by GC for volatile chemicals, and genotyped with the use of TRAP (Target Region Amplification Polymorphism) technique.  Over fifteen hundred polymorphic markers were amplified from DNA samples extracted from young leaf tissue with just two sets of PCR reactions.  One of the fixed primers was designed against the conserved plant telomere-repeat sequence (TTTAGGG)_n and the other a sunflower (Helianthus annus L.) Expressed Sequence Tag (EST) with homology to an Arabidopsis homeobox gene. In the PCR reaction each fixed primer was combined with four arbitrary primers labeled with fluorescent dyes and the amplified products were analyzed on the ABI 3730 DNA Analyzer.  These TRAP markers effectively discriminated each genotype of the 96 scented geraniums and are useful for clarifying plant identity and assessing genetic relationships.  In the resulting dendrogram from cluster analysis, scented geraniums that are clustered closely together also share strikingly similar morphological characteristics and volatile chemical GC profiles.