Beyond Terpenoids: Methoxy-Phenyl-oxime As the Major Volatile in a Novel Phalaenopsis Cultivar.

Floral scent is a primary determinant of pollinator attraction and reproductive success in the Orchidaceae family. In the genus Phalaenopsis, floral volatiles are typically dominated by terpenoids; however, this study identifies a significant exception in the novel cultivar Phalaenopsis DSM2049. Utilizing thin film solid phase microextraction (TF SPME) coupled with thermal desorption-gas chromatography-mass spectrometry (TD-GC-MS), Methoxy-Phenyl-Oxime (MPO) was identified as the predominant floral volatile. Mass spectrometry confirmed a molecular formula of C₈H₉NO₂, characterized by a molecular ion at m/z 151 [M]⁺, a base peak at m/z 133 [M-H₂O]⁺, and a phenyl ring at m/z 77. The compound was detected as two distinct E/Z geometric isomers with retention times of 12.35 and 12.32 minutes. MPO emission followed an extreme diurnal ON/OFF rhythm, with peak levels at 07:30-09:00 being 13.4-fold higher than those recorded at 01:30-03:00, while only trace amounts were detectable by mid-afternoon. These findings represent the first report of an oxime as the dominant scent component in Phalaenopsis, challenging the conventional view of terpenoid exclusivity in the genus and suggesting a highly regulated biosynthetic mechanism with specialized ecological implications for pollinator recruitment.