Effects Of Soybean Variety And Induced Defenses On Host Selection And Foraging Behavior Of Meteorus Pulchricornis

The constitutive and induced plant defenses both are plant defensive responses to herbivore feeding,having negative impacts on herbivores in host selection,development,and reproduction.They can also influence natural enemies of the herbivores in foraging,selecting behaviors and developmental performances.It is therefore pertinent to understand processes in plant resistance and its effects on phytophagous insects and their parasitic natural enemies.And this knowledge provides data for us to deal with pest outbreaks.In this thesis study,I first made dual-choice trials to examine if the parasitoid discriminate between hosts feeding on different soybean plants(3 varieties)induced by different feeding styles,and then investigate parasitoid foraging behaviors in response to soybean plants under the treatments.Following main results and conclusions were obtained.1.Host selection behavior of Meteor us pulchricornisThe Y-tube olfactometer was used to do the choice experiment.M.pulchricornis performed significant preferences between hosts induced by Spodoptera exigua caterpillar's feeding and the control,choosing the control host for 74 choices among 90 choice trials.M.pulchricornis performed significant preferences between hosts induced by Aphis glycines caterpillar's feeding and the control,choosing the control host for 73 choices among 90 choice trials.M.pulchricornis performed no significant preferences between hosts induced by Spodoptera exigua and Aphis glycines caterpillar's feeding and the control,choosing the control host for 43 choices and 47choices among 90 choice trials.The results of this study suggest that M.pulchricornis can relatively discriminate hosts receiving feeding treatment by chewing or sucking insects.2.Effects of soybean variety and induced defenses on Meteorus pulchricornis foraging behavior Two-way factorial experiment design,including soybean variety(high,medium and low in constitutive resistance)and induced resistance(fed by Spodoptera exigua larva,Aphis glycines feeding,and the control)as treatments,was used to investigate foraging behaviors of Meteorus pulchricornis.Following behaviors were affected by the treatments.(1)The"number of hosts stung once" was not affected by the soybean variety,but it was by the feeding treatment,being 9.6 for A.glycines feeding,9.0 for S.exigua larval feeding,50.0%and 40.6%more than that for the control,respectively.(2)The "number of healthy hosts given-up after stung" was influenced by interaction between soybean variety and feeding treatments.It was different for the high-resistant variety between two feeding treatments each and the control,being 49.4 for S.exigua larval feeding 50.3 for A.glycines feeding treatments,7.15%and 10.2%more than that for the control.(3)The "number of host given-up after stung" was not influenced by the feeding treatments,but was by the soybean variety.It was higher for the low constitutive resistance(2.4)than for the high(1.2).(4)The "number of ovipositor protruding" was not influenced by the soybean variety,was the feeding treatment,2.6 for A.glycines feeding,and 3.6 S.exigua larval feeding,4.0%and 44.0%more than that for the control,respectively.(5)The "time interval between the last stinging and departure" was influenced by interaction between soybean variety and feeding treatments,the effect owing to the difference between A.glycines feeding and the control for the high constitutive resistant soybean.(6)The "number of leaves searched" was not influenced by the soybean variety,but was by the feeding treatment,10.1 leaves for S.exigua larval feeding,10.5 leaves for A.glycines feeding,7.45%and 11.7%more than that for the control,respectively.The results of this study suggest that M.pulchricornis foraging behaviors can be influenced by both constitutive and feeding-induced soybean defenses,both directly and indirectly.