Deciphering the Chemical Fingerprint of Astragalus membranaceus: Volatile Components Attractive to Bruchophagus huonchili Wasps

Simple SummaryBruchophagus huonchiliis a serious threat to the yield and quality of the Chinese medicinal herbAstragalus membranaceusseeds. Plant volatile organic compounds (VOCs) are essential signaling substances for herbivorous insects when searching for host plants and mating partners. In this study, we collected and identified the VOCs emitted fromA. membranaceuspods and evaluated the attraction of individual and combined compounds toB. huonchili. Our results showed that specific concentrations of five VOCs (cis-β-ocimene, hexyl acetate, hexanal, decanal, and β-caryophyllene) attractB. huonchiliwasps. Moreover, our findings revealed that three formulations exhibited strong attraction toB. huonchiliin Y-tube olfactometer assays and in the field. This study suggests that a blend with specific VOCs and ratios emitted fromA. membranaceuscould be used as attractants in traps forB. huonchilimonitoring in the field.AbstractBruchophagus huonchiliis a pest that poses a serious threat to the yield and quality ofAstragalus membranaceusseeds. In this study, we employed solid-phase microextraction (SPME) and gas chromatography-mass spectrometry (GC-MS) to identify volatile organic compounds (VOCs) inA. membranaceuspods during the pod-filled period. Additionally, we utilized a Y-tube olfactometer to measure the behavioral response ofB. huonchilito different individual VOCs and specific VOC-based formulations. The most effective formulations were further evaluated for their effectiveness in attracting wasps in the field. Our findings revealed thatA. membranaceuspods emit 25 VOCs, including green leaf volatiles (GLVs) and terpenoid and aromatic compounds. Among these compounds, five were found to be most attractive toB. huonchiliat the following concentrations: 10 µg/µL cis-β-ocimene, 500 µg/µL hexyl acetate, 100 µg/µL hexanal, 1 µg/µL decanal, and 10 µg/µL β-caryophyllene, with respective response rates of 67.65%, 67.74%, 65.12%, 67.57%, and 66.67%. In addition, we evaluated 26 mixed VOC formulations, and three of them were effective at attractingB. huonchili. Furthermore, field experiments showed that one of the formulations was significantly more effective than the others, which could be used for monitoringB. huonchilipopulations.Keywords:seed wasps;Astragalus membranaceuspods;plant volatiles;attractants