Temporal characterization of 2-phenylethanol in strongly and weakly scented genotypes of damask rose

The molecular and physiological properties of 2-phenylethanol (2-PE) in the strongly scented genotype (SSG) and a weakly scented genotype (WSG) of damask rose at six floral developmental stages were investigated. The chemical compositions of volatile emissions were determined by gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS) analysis of the floral headspace. In both genotypes, the relative percentage of 2-PE increased more in SSG than WSG, as flowers developed. In the petals of damask rose the relative transcript levels of phenyl acetaldehyde reductase (PAR) were higher at stages 3 and 4 in SSG and WSG, respectively. Also, the expression pattern of PAR indicated a significant difference between two genotypes during flower developmental stages. In this study, enzymatic activity leading to the synthesis of 2-PE from the phenyl acetaldehyde (PAld) moderately increased during flower development up to stage 5 in SSG. However, high level of PAR enzymatic activity was observed in stage 3 of WSG. These results indicated that the pattern activity of PAR was different in two used genotypes of damask rose. For SSG, PAR activities were low in early stage of flower development and then gradually increased reaching its highest value at full bloom stage. In WSG, no significant change in enzyme activity was seen after stage 3.