| The brown planthopper Nilaparvata lugens（BPH）is a monophagous pest of rice.The Cyrtorhinus lividipennis is an important predator of the BPH.In this study,the exogenous calcium（Ca）initiation treatment on rice was carried out at the seed stage,changes of the survival rate,honeydew secretion,body weight growth rate,selection and feeding behavior of BPH fed on rice plants with or without exogenous calcium treatment were analyzed,changes in the selection and predation behavior of Cyrtorhinus lividipennis on BPH was tested as well.Using GC-MS and olfactory,we analyzed changes of volatile composition and content of rice plants and the effects on the selection behavior of BPH and Cyrtorhinus lividipennis.The results of our study have laid a theoretical foundation on ecological control of BPH in the field.The main results are as follows:1 Effects of exogenous calcium in rice on feeding and selection behavior of BPHRice seeds were soaked in 20 mmol/L CaCl2solution,and the control seeds were soaked in distilled water.At the tillering stage,nymph survival rate,honeydew secretion,body weight growth rate,selection behavior and feeding behavior of BPH fed on rice plants with different treatments were compared,the results showed that:（1）survival rates of the 2nd BPH nymphs fed on Ca-treated rice plants were significantly5.61%、7.12%、13.01%、18.01%and 20.38%lower than those fed on control plants after 3-7 days,respectively;The honeydew secretion of BPH fed Ca-treated rice plants were 42.49%lower than those fed on control plants,the body weight growth rate of BPH was 5.90%lower than those fed on control plants,（2）Analysis of selection behavior showed that the BPH female adult preferred to select H2O-treated rice plants regardless of whether BPH were fed on rice plants or not.（3）The EPG parameter results showed that the frequency of occurrence of np wave and ph wave by BPH fed on Ca-treated rice plants were significantly more than those of fed on control plants,the N4-a and N4-b waves frequency were significantly reduced,but the occurrence of N5wave frequency did not different from those fed on control plants;The duration of the first np wave and its total duration,the total duration of the ph wave were significantly prolonged,the total duration of the N4-a,N4-b and N5 waves were significantly shortened.These results indicates that Ca-treated rice plants obstructs the feeding of BPH in xylem and phloem.2 Effects of exogenous calcium in rice on the predation Cyrtorhinus lividipennis on BPH eggs and nymphs（1）The selection behavior of Cyrtorhinus lividipennis was detected by using the Y-tube olfactory,and the results showed that:in the absence of BPH feeding,there was no obvious difference in the selection of Cyrtorhinus lividipennis to Ca-treated rice plants and control plants;in the case of infestation of BPH,the number of Cyrtorhinus lividipennis selected Ca-treated rice plants was obviously more than those selected control plants.the results of shrouded experiment also showed that Cyrtorhinus lividipennis preferred to choose Ca-treated rice plants.（2）the predation rates of Cyrtorhinus lividipennis on the 1st BPH nymphs in Ca-treated rice plants after 24 and 48 h were 4.83%and 9.50%higher than those preyed on control plants,.and the predation rates of Cyrtorhinus lividipennis on BPH egg in Ca-treated rice plants after 24 h was 13.72%higher than those preyed on control plants.3 Effects of exogenous calcium in rice on volatiles in rice plants and single volatile verificationUsing GC-MS to detect the volatiles released by Ca or H2O-treated rice plants infested with or without BPH,the results showed that:（1）A total of 57 volatile substances were detected in all Ca and H2O-treated rice plants not infested by BPH,content of methyl salicylate and 1-octen-3-ol in Ca-treated plants were 122.53%and195.70%higher than that of H2O-treated plants,the release ofβ-caryophyllene was43.42%lower than that of the H2O-treated plants;Under damage of BPH,a total of 35volatile substances were detected in all Ca and H2O-treated rice plants,the content of methyl salicylate and 1-octen-3-ol released from Ca-treated plants were 326.00%and428.55%higher than that of the H2O-treated plants,while there was no significant difference in content ofβ-caryophyllene between plants with different treatment.（2）Using"H"olfactometer to test the choice of BPH to the four signa voltiles,methyl salicylate,1-octen-3-ol,β-caryophyllene and（E）-2-hexenal,paraffin oil was taken as control,the results showed that:the number of BPH that chose 1,10 and 100μg/μL methyl salicylate was 25.00%,44.83%and 68.49%less than those chose paraffin oil（control）,respectively,the number of BPH that chose 10 and 100μg/μL 1-octen-3-ol was 59.42%and 72.97%less than those chose control,the number of BPH chose10μg/μLβ-caryophyllene was 44.83%less those chose control,while there was no significant difference in the number of BPH between those chose（E）-2-hexenal and control.（3）Using"Y"olfactometer to test the choice of Cyrtorhinus lividipennis to 10μg/μL methyl salicylate,1-octen-3-ol,β-caryophyllene and（E）-2-hexenal,the results showed that the number of Cyrtorhinus lividipennis chose methyl salicylate and 1-octen-3-ol were 100%and 100%higher than those chose paraffin oil,but Cyrtorhinus lividipennis did not choseβ-caryophyllene and（E）-2-hexenal obviously.Collectively,our results indicates that seed soaking with CaCl2significantly improves rice resistance to BPH,and it is beneficial to the predation of the BPH eggs and nymphs by Cyrtorhinus lividipennis.Ca-treated rice plants released more methyl salicylate and 1-octen-3-ol and these two volatiles showed obvious repellent effect on BPH,and showed obvious attraction effect on Cyrtorhinus lividipennis.These results provided a theoretical foundation for the ecological control of brown planthopper by regulating the tritrophic relationship between rice,brown planthopper and Cyrtorhinus lividipennis by using exogenous calcium... |
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