Gustory Response Characteristics Of Helicoverpa Armigera (hübner) Larva And Screening Of Aroma Plant-derived Feeding Deterrents

The author studied the gustory response of Helicoverpa armigera lavae to human’sbasic tastants, then a serial of bioassay-guided chemical analyses was used to isolate the activecomponents from28aroma plant species. Finally, we designed some extention bioassays on theeffects of two active compounds, sanshool and piperine, on different insect species, with defferentstarvation periods, and with different dosages. The main results are shown below:(1) Choice feeding response of H. armigera to different combinations of human basic tastants.Six tastants were tested, including sour (citric acid), sweet (sucrose), bitter (quinine), salty (NaCl),numb-taste (Zanthoxylum bungeanum extract), and hot-taste (Capsicum annuum extract). Theresult shows that the larvae showed relatively higher choice feeding percentages to the tobaccoleaf discs treated with sweet-, bitter-, and hot-taste sunbstances, while shows relatively lowerfeeding amount to those treated with salty-, sour-, and numb-taste substances. Under the choicecondition, the feeding amount shows positive relationship with the doses of Z. bungeanum extract,but under non-choice feeding condition, the feeding amount was significantly related to the dosesof NaCl.(2) Interactions between Zanthoxylum bungeanum ethanol extract and NaCl. We optimizedthe matrix and extracting solvent suitable for feeding deterrent bioassay, then designed a serial ofblends of Zanthoxylum bungeanum ethanol extract and NaCl solutions and guided by bioassays.The result shows that ethanol was the most suitable solvent for extraction of active feedingdeterrent. Both solution exhibited a dose-dependent response when used alone, and both peaked at30μL, when combined, they acted synergistically, and the optimal ratio of Z. bungeanum ethanolextract to NaCl was25/15, with the highest anti-feeding percentage of98%. When the dose of theoptimized blend was applied as30μL, feeding was inhibited compeletely.(3)Systemitical screening of active plant resources.The effects of ethanolic extracts from28aroma plant species was tested systemically. And the result shows that three Piper species,respectively black piper, white piper, and P. longum, as well as an Umbelliferae species, Angelicadahurica, showed the strongest anti-feeding activities, stronger that the extract of Z. bungeanum.(4)Isolation and identification of the active compounds in black piper and Z. bungeanum: weobtained11rinses of Zanthoxylum bungeanum using the following solvent system: n-hexane (2×15mL), ether (2×15mL), dichloromethane (2×15mL)，and alcohol (5×15mL), and obtained9rinses of Piper nigrum using the following solvent system: n-hexane (15mL), ether (2×15mL),dichloromethane (2×15mL)，and alcohol (4×15mL), then conducted a bioassay on the deterrenceof these rinses on the food consumption of Helicoverpa armigera larvae, and the activecomponents were identified using gas chromatography–mass spectrometry technologies. Thebioassay indicates that all the rinses of Z. bungeanum had extremly significant effect on thefeeding, except for the first rinse of n-hexane and the first rinse of ether, however, all the rinses ofPiper nigrum deterred the feeding of H. armigera extremly significant. The active rinses showingextremly significant deterrence were combined and performed on GC-MS, and the major volatileand unvolatile components of Z. bungeanum were D-limonene and linalool as well as sanshool,respectively; while the major volatile and unvolatile components of P. nigrum were β--phellandrene,3-carene, and β-caryophyllene, as well as piperine. We tentatively concluded thatsanshool and piperine were the major antifeedant components for they shared common structuresof ampicins.(5) Effects of different combinations of piperine and sanshool on feeding of H. armigeralarvae. Based on the results mentioned above, different doses of piperine and sanshool weremixed and tested their anti-feeding activities. When the sanshool was applied alone with doses of2μL or4μL, showed no effect. However, when the sanshool was added to piperine, the feedingdeterrence was increased with increasing doses of sanshool, suggesting that these two amidesacted synergistically.(6) Extention bioassays. Firstly, we compared sanshool and piperine with a knownbroad-spectrum feeding deterrent, azadirachtin, the result shows that the effect of piperine had nosignificant difference with that of azadirachtin, while the effect of sanshool was remarkablylower than piperine and azadirachtin, and had no significant with that of the control. The larvaeof H. armigera and Pieris rapae with140hr and114hr starvation periods were exposed tosanshool and piperine, respectively, to elucidate whether these species with different feedinghabits would show somewhat habituation. The result shows that the feeding amounts of leafdiscs treated with the solutions of both compounds did not increasing along with exposure timeprolonged, suggesting that these two compounds should be promising feeding regulators underfield conditions. Piperine exhibited fairly strong anti-feeding effect on the larvae of Spodopteraexigua, Proxenus lepigone, and Mythimna separate, however, the response sensitivities of thesecaterpillars to sanshool were spicies-specific.