Effect Of Induced Plant Response By Phytophagous Pests On Host Selection Behaviors And Oviposition Of Whitefly Bemisia Tabaci

Herbivores are known to induce various plant defenses,which may negatively affect on subsequent herbivores,such as host preference,settling,growth,oviposition ability.The whitefly Bemisia tabaci and the mealybug Phenacoccus solenopsis are common sap-sucking pests,have broad host distributions,and can coexist on the same plant in the field.The carmine spider mite Tetranychus cinnabarinus,a cell-content feeder,is also important economic pest.In this study,two different herbivors(T.cinnabarinus and P.solenopsis)were pretreated on the cucumber or tomato.Then,defensive enzymes of treated plants and their related gene of JA or SA pathways were analyzed.Finally,the detoxification,digestive and protective enzymes in whiteflies were also tested to reveal the effect of induced plant response.The main results are showed as following: 1)In the choice or no-choice tests,more whiteflies selected the untreated plants than selected pretreated plants by mealybugs.In contrast,more whiteflies selected pretreated cucumbers by spider mites than selected untreated cucumbers,and produced more eggs.However,pretreated tomatoes by spider mites only could attract more whiteflies in no-choice tests signally.2)The activities of LOX,PAL,POD and PPO were significantly increased through the induced response on cucumber by spider mites.The spider mites could induce the activities of LOX,PAL and POD in tomato significantly.Similarly,the activities of LOX,PAL and POD in cucumber were significantly increased by feeding mealybugs.The mealybugs significantly induced LOX activity,but significantly inhibited POD and PPO activities in tomato.After removing the pretreated pests,the PPO and POD activities were still highly induced persistently.3)The daily oviposition of B.tabaci on cucumber was positively correlated with activity of trehalase,and which on tomato was also related to activity of invertase.The activities of protective enzymes in B.tabaci were significantly increased after coexisted with T.cinnabarinus.4)The JA / ET-related genes(LOX,OPR3 and ETR)and the SA-related genes(PAL and POD)in cucumber were activated after treatment of spider mites for 12 h.However,if the feeding time was increased,all the up-regulated gene expression was decreased except LOX gene.LOX and PAL were activated after treatment of mealybugs for 12 h,but the genes related to ethylene pathway were significantly inhibited.After continuous feeding,the genes of SA pathway(PR1 and PR5)were also activated.LOX and ETR were significantly up-regulated,but PR1 was down-regulated after feeding coexisted with B.tabaci.The relative expression of Pin-2 and PI-II in tomato was significantly up-regulated after pretreated by spider mite for 12 h.LOXD,Pin2,PI-II,ETR1 and ETR3 were significantly up-regulated after continuous feeding for 3d.The expression of LOXD,PR1-? and ETR3 genes were significantly induced by both feeding whitefly and spider mite.The Pin2,PI-II and PR1-? gene were significantly up-regulated after pre-infection by mealybug for 12 h.Pin2 gene expression was significantly inhibited after continuous feeding for 3d,but the expression of LOXD,OPR3,NPR1 and ETR3 genes induced significantly.Pin-2 was significantly down-regulated and the relative expression of PI-II,PR1-?,ETR1 and ETR3 genes were significantly up-regulated after coexisting with mealybugs and whiteflies for 3d.In conclusion,T.cinnabarinus and P.solenopsis induced different plant defense activities on the same host,which affected to the biological behaviors of the whitefly subsequently through variation of the defense enzyme activity and the gene expression level of the defense pathway.Meanwhile,the digestive enzymes and protective enzyme of whitefly also play an important regulatory role in its biological behavior.