Preliminary Study On The Location Of The Parasitoids, Microplitis Mediator To The Solanum Host Plant

Some aspects of the interactions in the tritrophic system of three Solanum plants,the cotton bollworm, Helicoverpa armigera,and the parasitoid, Microplitis mediator,were studied in the laboratory.first,the host selection behaviour of Microplitis mediator were examined by choice tests using three host plant species(Lycopersicon esculentum,Solanum melongena,Capsicum frutescens) and the behavioural responses of Microplitis mediator to plant volatiles were bioassayed.Next,volatiles collected from the headspace of different plant treatments were collected and indentified.Headspace volatiles of tomato collected on Tenax were attractive to wsaps in a Y-tube tests,respectively.The chemical compositions of the volatiles collected from the host plant with Tenax-TA trap and were analyzed using GC-MS.Finally,plant-parasitoid interactions mediated by wound-induced green leaf volatiles were studied.The major results are summarized as follows:1. In a Y-tube bioassay,both volatiles from three host plants(Lycopersicon esculentum,Solanum melongena,Capsicum frutescens) were strongly attractive to Microplitis mediator.Tomato infested by H. armigera was more attractive to Microplitis mediator than undamaged plant. egg-plant and red paper plants infested by H. armigera have similar attractiveness to Microplitis mediator , and the parasitoid showed no preferences between them .2. In a Y-tube bioassay, generally,volatiles from tomato leaves infested by different instars H. armigera were strongly attractive to Microplitis mediator ,but there exist the significant difference among plants infested by different instars H. armigera. Plants infested by 2nd,3rd and 4th instars H.a were more attractive to Microplitis mediator than 1st,5th instars H.a .the results are listed as follows:♂:Plant infested by 4th H.ar> Plant infested by 2nd H.ar , Plant infested by 3rd H.ar > Plant infested by 1st H.ar , Plant infested by 5th H.ar♀:Plant infested by 4th H.ar> Plant infested by 2nd H.ar >Plant infested by 3rd H.ar > Plant infested by 1st H.ar , Plant infested by 5th H.ar3. The chemical compositions of the volatiles collected from the tomato infested by different instars H.ar were analyzed using GC-MS.Undamaged plants and tomato plants infested by different instars H. armigera both released 15 chemical compounds and ( E) -2-hexenal was the volatile organic compound with the highest content among them .These volatiles are composed of green leaf volatiles, terpenoids ( including monoterpenes, sesquiterpenes and their derivatives) and methyl salicylate (MeSA). Generally, plants infested by insects released larger amounts of volatiles than undamaged plants did. The experiment results show that volatiles from tomato leaves infested by H. armigera were strongly attractive to Microplitis mediator and this strong attraction to Microplitis mediator is depended on the significant difference among the content of chemical compounds . Additional experiments will be needed to identify these unkown compounds in the further.