Abstract: [Objective] Sea-buckthorn (Hippophae rhamnoides) is an important economic and ecological plant in the arid and semi-arid region of China, and Rhagoletis batava obseuriosa (Diptera:Tephritidae) (RBO) is a serious quarantine insect pest that damaged the plant fruit. In order to find the RBO-resistant clones, a field investigation and indoor test were carried out. The difference of the biochemical substances between the resistant- and sensitive-plants were investigated to provide the theoretical basis for further study of physiological and biochemical resistance mechanisms of sea-buckthorn to RBO.[Method] First, the difference of RBO adult's oviposition biology and fruit damage were compared between RBO-resistant clones and RBO-sensitive clones both in the field and in laboratory. Then, two stages:before the adult emergence and at the peak time of adult oviposition, were chosen to detect biochemical substances and enzyme activities in the fruits and leaves of the resistant- and sensitive-clones using gas chromatography-mass spectrometry (GC-MC) and high performance liquid chromatography (HPLC).[Result] 1) Sea-buckthorn clones resisting RBO were obtained by screening the fruit damage in the field and comparing the RBO ovposition rates indoors. 2) At the peak time of adult oviposition, the total phenolics, soluble protein and proline content in RBO-resistant clone were higher than those in RBO-sensitive clones, with increasing of 101.34%, 50.21% and 20.12% in the fruits, and 121.22%, 30.43% and 40.68% in the leaves, respectively. 3) The volatile compounds were significantly different in the fruits of the two clones. The types and contents of the esters in the RBO-resistant clones were significantly lower than those in the RBO-sensitive clones, while the content of alcohols was significantly higher than that in the RBO-sensitive clones. 4) The content of non-volatile kaempferol in RBO-resistant clones was significantly higher than that in the RBO-sensitive clones, with increase of 29.40% and 40.80% in fruits and leaves, respectively. The content of isorhamnetin in fruits of RBO-resistant was 43.20% higher than that in RBO-sensitive clones, while the content in the leaves was 41.34% lower than that in the RBO-sensitive clones. 5) At the peak time of adult oviposition, activity of the peroxidase (POD), chitinase and phenylalanine ammonialyase (PAL) in the fruits were 98.21%, 25.03%, and 20.10% higher, respectively, and the POD and PAL activities in the leaves of RBO resistant clones were 33.40% and 36.30% higher, respectively than those in RBO-sensitive clones.[Conclusion] There were significant differences in the secondary metabolites and enzyme activities in the sea-buckthorn fruits and leaves between the RBO-resistant clones and the RBO-sensitive clones. The results preliminarily revealed the physiological and biochemical characteristics of the RBO-resistance, and provided the basis for further study on the mechanism of the RBO-resistance and the new RBO-resistant clone breeding.

Key words: sea-buckthorn, Rhagoletis batava obseuriosa, insect-resistant, biochemicals, enzyme activity