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.

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.

Genetic differentiation of Helicoverpa armigera （Hübner） and H. assulta （Guenée） （Lepidoptera： Noctuidae） based on AFLP markers

Here we use amplified fragment length polymorphism （AFLP） to assess genetic differentiation of Helicoverpa armigera and H. assulta. The results indicated that both species-specific fingerprints and cluster analysis showed the ability of AFLP technique to discriminate the two sibling species; among a total 1963 AFLP markers amplified from nine primer combinations： 777 （39.6%） were H. armigera-specific, 602 （30.7%） were H. assulta- specific, and 584 （29.7%） were common bands. The mean number ofH. armigera-specific bands was significantly more than that of H. assulta-specific bands for nine primer combinations （P 〈 0.05）; the intraspecific distance of H. armigera and H. assulta was 0.123 0 and 0.110 7 respectively, and the interspecific distance was 0.178 3. In addition, the percentage of polymorphic loci and estimated average heterozygosity were used to estimate genetic diversity of the two species. This study therefore demonstrates that AFLP analysis is a sensitive and reliable technique to study genetic differentiation and genetic relationships between species and provides sufficient molecular markers for future linkage map conslruction, location and eventual cloning of genes involved in traits differentiation.

Identification, isolation and characterization of the antifeedant constituent of Clausena anisata against Helicoverpa armigera （Lepidoptera： Noctuidae）

Hexane, petroleum ether, chloroform, ethyl acetate, methanol and water extracts of Clausena anisata [（Willd.） Hook E Ex Benth] leaves and roots were evaluated against Helicoverpa armigera （Hubner） for antifeedant activities. Antifeedant activity was confirmed, and was found to be higher in root extracts than those of the leaf. Chloroform and petroleum ether extracts of the root showed strongest antifeedant activities （DC50s [concentration （C） causing 50% deterrence compared with the control] 0.014% and 0.016% respectively）, and root extracts were fractionated using silica gel column chromatography. One fraction of the chloroform and one of the petroleum ether root extracts was active; and on the basis of mass spectroscopy and ^1H and ^13C nuclear magnetic resonance spectral data, the active compounds in the two fractions were confirmed to be identical, and identified as osthol [2H-1-Benzopyran-2-one, 7-methoxy-8-（3-methyl-2-butenyl）]. The highest concentration of osthol was found in the chloroform root extract. Antifeedant activities of the root extracts, as measured by DC50 values, were highly correlated with their osthol contents. Approximately 99% of the variation in bioactivity of the root extracts could be accounted for by variation in osthol content; osthol therefore, appeared to be an antifeedant component of C. anisata to H. armigera. This may provide a new approach to managing this pest.