Study on the recognition mechanisms of sucking site by green leafhopper

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The green leafhopper Nephotettix cincticeps Uhler and Nephotettix virescens are known as pests of rice plants in most Asian countries. Their feeding behavior consists of two phases ; stylet insertion into plants followed searching and reaching a sucking sites, which is called as the probing behnavior, and sucking plant saps, which is called as the sucking behavior. It is said that these two phases are independently controlled by different factors. However It has not been clear why this insect can reach sucking site in the rice plant. In this study, the focus was put on the probing behavior. An attempt was made to be clear the problem.Through a preparative bioassay and chemical purify, the compound which strongly stimulates the probing behavior of N.cincticeps was isolated and identified as tricin 5-O-β-D-glucopyranoside.A few kinds of flavonoid including tricin 5-O-β-D-glucopyranoside were also isolated and identified as probing stimulants for oligophagous Sogatella furciffera Horvath and Laodelphax striatellus Fallen.On the other hand, eight kinds of C-glycosyl flavone have been reported as probing stimulants for Nilaparvata lugens which is known as monophagous insect. Judging from these results and report, there seemed to be some relationships between probing stimulants and host range of leafhoppers and planthoppers. That is, these results may show that monophagous insects require many kind of probing stimulants strictly to distinct their host plants and polyphagous insects which has a wide host range require a few probing stimulants to recognize many plants as host plants. It is hence considered that probing stimulant is host recognition substance.