The Insect Resistance Of The Jujube Tree Induced By MeJA And Its Impact On The Pest Japanese Wax Scale

The jujube tree, Ziziphus jujube Mill (Rhamnaceae) is one of the most important economic fruits in north China. Japanese wax scale, Ceroplastes japonicus Green (Hemiptera:Coccoidea:Coccidae) is a destructive pest in the jujube orchard. This research was conducted from2010.4to2011.10by continuous observation and specimen collection in the fixed experiment orchards, which located at Jishan County, Shanxi Province, combining with the test and analysis in laboratory. The purpose of this research is to study the effect of Methyl jasmonate (MeJA) as an exogenous signal molecule on the insect-resistance physiological reaction of jujube tree and the effectiveness on the control of the pest, Japanese wax scale.The part one:In this paper, jujube trees, Z. jujube were treated with MeJA, in order to study the physiological reaction of the induced insect-resistance. The three key enzymes PLO、LOX and AOS, driven the biochemical reaction in the jasmonic pathway were determined. And the quantity of honeydew excretion and the quantity of nymphs fixed on the leaves and the development size of body were measured which were the adult females of Japanese wax scale, C. japonicus, The results show that after treated with MeJA, the enzyme activity of PLO raised49.99%-105.10%, the LOX activity increased45.99%-146.05%and the AOS activity rise50.55%-163.34%of the leaves of the jujube trees. This indicated the MeJA, as an exogenous signaling molecule, indeed induced the anti-insect reaction of the jujube trees. The quantities of honeydew secreted by the wax scale living on the jujube trees decreased62.25%,52.43%and39.54%(measured by area), respectively, in the tree time periods each day. Meanwhile, in the measured method by weight, the decrease rates were39.17%,36.03%and34.05%, respectively. In similar, the honeydew secretion dropped down28.34%and42.86%(measured by area), in the3day successive experiment. While the reduction rate reach21.51%and24.73%(measured by weight). This showed the obvious repression effect on the feeding and digestion of the scale insect under the condition of the anti-insect reaction of the plants induced by MeJA. Secondly, the number of first instar nymphs fixed leaves in the control group was145, while in the treatment group was65. After90days the nymph development, the size of the control group worms is large, during0.5-1.0mm range accounted for85.5%, while the size of treatment group parasites was small, only0.1-0.5mm range accounted for89.2%. This further validates the resistance to insects MeJA-induced hasing played an inhibitory effect on scale insects feeding and digestion. This result provided a new evidence for the plant’s induced anti-insect, and pointed out a new way for biological control of scale insects.The part two:We studied the impact of the chemical composition of the jujube tree volatiles treated by different doses and different treatment time MeJA. Experiment was conducted in May, July and September, respectively. The results show that contrasting the changes of the volatile of the jujube trees that were induced with Methyl-Jasmonic (MeJA), an exogenous signaling material, or were attacked by adults of the scale insect, C.japonicus in May. The headspace volatile trapping instrument was used to collect volatiles from jujube trees. The chemical components of the collected volatiles were analyzed using chromatography/mass spectroscopy (GC/MS). The results showed that the volatile substances were changed both in the components and in emission quantity when the jujube trees treated with MeJA or damaged by the scale insect.22components were examined from the volatile samples from the MeJA-treated jujube tree, and their emission quantity was37347ng/h. Meanwhile,24components were determined in the volatiles from the scale insect-damaged jujube trees, and their emission quantity reached54292ng/h. In comparison,14compounds were detected only in the volatiles of the health trees (as control), and the total emission quantity was18611ng/h. The difference reached the significant level either between the MeJA-treated section and the control section or between the scale insect-damaged section and the control section. In which, the increases of terpenoid, alcohol and ester compounds are especially significant in plant’s induced chemical defence. These compounds were considered to associate with the natural enemy recruitment in the biological pest control.Compared the impact of the jujube tree volatiles that treated by different concentrations of MeJA in July. The measuring results indicate that the chemical components and emission quantity of the jujube tree volatiles treated respectively by concentration of20μl,100μl and200μl MeJA has been increased compared with the control jujube trees. When the concentration of MeJA was20μl, the volatiles content of jujube tree is highest, which is120497ng/h, as the concentration of MeJA was100μl and200μl, the volatiles content of jujube tree is52385ng/h and41542ng/h separately, which both were higher than the normal jujube trees,32270ng/h. While the kinds of chemical composition of volatile of the jujube trees treated by three different kinds of concentrations of MeJA are the same,28kinds, higher than the normal jujube trees,19kinds.Compare the changes of the jujube tree volatiles treated by MeJA continually in September. The results appear that the components and emission quantity of the volatile substances increase gradually in continue threes days treated by MeJA and the kinds of volatiles is respectively20、22and25, the emission quantity of the volatile substances is19315ng/h,28537ng/h, and62323ng/h, respectively.The increase of terpenes, alcohols and esters is particularly evident, which is three kinds of the Jujube tree Volatiles in the above-mentioned three months, and these compounds were considered significant in plants induced chemical defense, these compounds are usually considered very important components which are related to attract natural enemy insects.