| Leptocybe invasa Fisher&La Salle(Hymenoptera:Eulophidae),a gall-inducing wasp onseveral Eucalyptus spp, was found in the Middle East and the Mediterranean region in2000.Leptocybe invasa was first reported in Dongxing town,Dongxing City, Guangxi in China.Leptocybe invasa displays thelytokous reproduction.The massive presence of galls in youngtree plantations and nurseries drew attention not only to the severe damage inflicted on infestedtrees but also to the potential for causing serious economic damage to the Eucalyptus forests inthe area. It will pose enormous threats to the development Eucalyptus industry in China. Thisessay has surveyed the present situation of Eucalyptus damaged by Leptocybe invasa inGuangdong province. In order to explore the resistance mechanism, the author has carried outresearches on the changes of some physio-biochemial indexes of inclusion, secondarymetabolites and defense enzymes of24Eucalyptus clones hazarded by Leptocybe invasa, andthe different expression of gene among different resistance Eucalyptus clones to Leptocybeinvasa. This essay is of great significance on the development and utilization of Eucalyptresources。The main conclusions are as follows:(1)The most seriously damaged region by Leptocybe invasa spreads from Zhanjiang toMaoming in Guangdong. Also, the lesser harmed area covers Yangjiang and Jiangmen.Infections have seldom been found in Northern region of Guangdong. DH201-2and E. exsertaare the main victim.In the nursery, most of the Eucalyptus clones seeding was damaged byLeptocybe invasa. The new shoots and buds growth is badly inhibited and the internodebecomes shorter than normal. The whole seeding appears smaller than any other whendamaged by Leptocybe invasa. In woodlands, Leptocybe invasa destroyed the young plantationwhich grows less than1year. The forest yield declined because the young plantation seriuoslyinfected by Leptocybe invasa leads to some trees death. (2)The growth and susceptibility to Leptocybe invasa is measured for a trial at the ageof5and7in Xinhui County,Guangdong Province. The result showed there were no significantcorrelations between damage index and other growth traits. Independent culling method wasused to select six good clones Susceptibility of sixty E.urophylla clones to Leptocybe invasawas controlled by resistance genes, we can obtain the clones which is promising forresistance to Leptocybe invasa through clones selection.(3)There was significant difference between the resistant of the24Eucalyptus clones.According to their disease incidence and infection indexes under the natural condition, the24Eucalyptus were classified as high resistant clones(E. urophylla A107, E. urophylla T121, E.urophylla D48, E.tereticornis Et16, E.pellita, E.dunnii, E. citriodora, E.cloeziana, E.urophylla×E.urophylla×E.camaldulensis M1and E.urophylla×E.grandis GL9), middleresistant clones(E.tereticornis Et12, E.tereticornis Et09, E.grandis KX8, E.grandis KX3,E.grandis KX12, E.urophylla×E.tereticornis L11, E.urophylla×E.grandis DH19-6,E.urophylla×E.tereticornis LH1, E.urophylla L9, E.urophylla×E.grandis DH42-6,E.urophylla×E.grandis DH32-26F2and E.urophylla×E.grandis DH32-29) and highsusceptible clones(E.grandis×E.tereticornis,DH201-2and E. exserta)(4)The author has studied the damage indexes and changes of some physio-biochemialindexes of the24Eucalyptus hazarded by Leptocybe invasa. There were no significantdifference of soluble protein and soluble sugar among three resistance type before theEucalyptus were destroyed by Leptocybe invasa, but increased significantly after beingdamaged. Especially, in contrast to the control, the soluble protein and soluble sugar of the highsensitive type shows remarkable differences. The descending sequence among inclusion ofdifferent resistance clones is high-sensitive clones, middle-resistant clones and high-resistantclones. The result showed that its increase is an important physiological response of Eucalyptusto Leptocybe invasa.(5)We had selected24different resistant Leptocybe invasa Eucalyptus clones to study theeffect of Leptocybe invasa on activites of superxide dismutase, peroxidase and polyphenol oxidase. The result showed the variation tendency of SOD, POD and PPO, the descendingorder of which are 'high-resistant clones, middle-resistant ones and high-sensitive onesbefore clones were determined by Leptocybe invasa Fisher&La Salle. The activities of SODand PPO in all clones initially increased then declined when the clones were invaded byLeptocybe invasa. The top three clones of increased incremental is, E. Citriodora,E.pellita andET12. The top three which declines are Et09,DH32-29and KX12. The activities of POD in allclones initially increased to stabilize. The top three clones of increase incremental, A107,T121and DH42-6.Variance analysis showed that there exists huge difference of activities of defenseenzymes's variation between the high-resistant and high-sensitive. Activities of defenseenzymes can be used as a biological and chemical target to assess the resistance of Eucalyptusto Leptocybe invasa.(6)Studies were conducted on the change of secondary metabolite content of24Eucalyptus hazarded by Leptocybe invasa. The result showed that the flavonoids contentincreased significantly of24Eucalyptus clones after being damaged by Leptocybe invasa, andthe flavonoids content of high sensitive clones is significant lower than other clones. Theincreasing amplitude of flavonoids content is remarkably/noticeably lower than that of clonesafter being damaged. The descending variation tendencies of tannins were high-resistant clones,middle-resistant clones and high-sensitive clones. The tannins declined when the clones wasinfected by Leptocybe invasa because it was used to defend the damaged ones. Therefore, thetannins in it continue to rise.(7) High-resistant clones (E. urophylla A107)and high-sensitiveones(E.grandis×E.tereticornis, DH201-2) were chosen to make RNA sequencing.971differential expression sequences were screened through de novo assembly and differentialexpression analysis for sequence.19target genes were chosen to make RT-PCR. The resultshowed that the target gene have a good specificity amplification except the target gene16. Theaverage amount of expression of G1,G5,G9,G10,G18and G19in sample B is significanthigher than in sample A. The average amount of expression of G3,G4and G11in sample A is significantly higher than in sample B. There were no significant differences of the averageamount of expression among the last target gene.
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