Revisiting the sex pheromone of the fall armyworm Spodoptera frugiperda,a new invasive pest in South China

The fall armyworm Spodoptera frugiperda is a worldwide serious agricultural pest,and recently invaded South China.Sex pheromone can be employed to monitor its population dynamics accurately in the field.However,the pheromone components previously reported by testing different geographic populations and strains are not consistent.On the basis of confirming that the S.frugiperda population from Yunnan Province belonged to the com strain,we analyzed the potential sex pheromone components in the pheromone gland extracts of females using gas chromatography coupled with electroan-tennographic detection(GC-EAD),gas chromatography coupled with mass spectrometry(GC-MS)and electroantennography(EAG).The results show that(Z)-9-tetradecenal acetate(Z9-14:Ac),(Z)-11-hexadecenyl acetate(Z11-16:Ac),(Z)-7-dodecenyl acetate(Z7-12:Ac)or(E)-7-dodecenyl acetate(E7-12:Ac)with a ratio of 100:15.8:3.9 induced EAD responses to varying degrees:Z9-14:Ac elicited a strong EAD response,Z7-12:Ac or E7-12:Ac elicited a small but clear EAD response,while Z11-16:Ac elicited a weak EAD response.Further single sensillum recording(SSR)showed that Z9-14:Ac and Z7-12:Ac induced dose-dependent activities in two types(A and B)of sensilla in male antennae,respectively,while the sensilla in response to E7-12:Ac and Z11-16:Ac was not recorded.Finally,wind tunnel tests reveal that Z9-14:Ac and Z7-12:Ac are two principal sex pheromone components of the tested population.

Functional map of the macroglomerular complex of male Helicoverpaarmigera

The mechanism of sex pheromone reception in the male cotton bollworm Helicoverpa armigera has been extensively studied because it has become an important model system for understanding insect olfaction.However,the pathways of pheromone processing from the antenna to the primary olfactory center in H.armigera have not yet been clarified.Here,the physiology and morphology of male H.armigera olfactory sensory neurons(OSNs)were studied using single sensillum recording along with anterograde filling and intracellular recording with retrograde filling.OSNs localized in type A sensilla responded to the major pheromone component cis-11-hexadecenal,and the axonal terminals projected to the cumulus(Cu)of the macroglomerular complex(MGC).The OSNs in type B sensilla respondcd to the bchavioral antagonist cis-9-tetradecenal,and the axonal terminals projected to the dorsomedial anterior(DMA)unit of the MGC.In type C sensilla,there were 2 OSNs:one that responded to cis-9-tetradecenal and cis-11-hexadecenol with the axonal terminals projecting to the DMA,and another that responded to the secondary pheromone components cis-9-hexadecenal and cis-9-tetradecenal with the axonal terminals projecting to the dorsomedial posterior(DMP)unit of the MGC.Type A and type B sensilla also housed the secondary OSNs,which were silent neurons with axonal terminals projected to the glomerulus G49 and DMP.Overall,the neural pathways that carry information on attractiveness and aversiveness in response to female pheromone components in H.armigera exhibit distinct projections to the MGC units.

Functional types of long trichoid sensilla responding to sex pheromone components in Plutella xylostella

Sex pheromones,which consist of multiple components in specific ratios pro-mote intraspecific sexual communications of insects.Plutella xylostella(L.)is a world-wide pest of cruciferous vegetables,the mating behavior of which is highly dependent on its olfactory system.Long trichoid sensilla on male antennae are the main olfactory sen-silla that can sense sex pheromones.However,the underlying mechanisms remain unclear.In this study,3 sex pheromone components from sex pheromone gland secretions of P xy-lostella female adults were identified as Z11-16:Ald,Z11-16:Ac,and Z11-16:0H in a ratio of 9.4:100:17 using gas chromatography-mass spectrometry and gas chromatography with electroantennographic detection.Electrophysiological responses of 581 and 385 long trichoid sensilla of male adults and female adults,respectively,to the 3 components were measured by single sensillum recording.Hierarchical clustering analysis showed that the long trichoid sensilla were of 6 different types.In the male antennae,52.32%,5.51%,and 1.89%of the sensilla responded to Z11-16:Ald,Z11-16:Ac,and Z11-16:0H,which are named as A type,B type,and C type sensilla,respectively;2.93%named as D type sen-silla responded to both Z11-16:Ald and Z11-16:Ac,and 0.34%named as E type sensilla were sensitive to both Z11-16:Ald and Z11-16:OH.In the female antennae,only 7.53%of long trichoid sensilla responded to the sex pheromone components,A type sensilla were 3.64%,B type and C type sensilla were both 0.52%,D type sensilla were 1.30%,and 1.56%of the sensilla responded to all 3 components,which were named as F type sen-silla.The responding long trichoid sensilla were located from the base to the terminal of the male antennae and from the base to the middle of the female antennae.The pheromone mixture(Z11-16:Ald:Z11-16:Ac:Z11-16:0H=9.4:100:17)had a weakly repellent effect on female adults of P xylostella.Our results lay the foundation for further studies on sex pheromone communications in P.xylostella.