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In the dissertation, the effect of the exogenous Methyl salicylate (MeSA) onto the tea plant (Camellia sinensis) on feeding behavior of tea green leafhopper (Empoasca vitis Gothe), on the activities of the defensive enzymes phenylalanine ammonia-lyase (PAL) and lipoxygenase (LOX), on the content of defensive molecules H2O2, and on the expression of PAL and LOX genes were transacted in the laboratory. The attracting effect of MeSA, which was tardily emitted, to the primary natural enemies was investigated in tea gardens. The MeSA-induced direct and indirect resistance mechanism of tea plants to tea green leafhoppers was discussed.The feeding behaviors of tea green leafhopper on tea plants were monitored by DC-EPG. Main seven types of waveforms produced by tea leafhopper probing were confirmed, including A waveform—stylet pathway formation, S waveform—salivation, C waveform—active ingestion, E waveform and F waveform—passive ingestion, R waveform—the insect resting with its stylet inserted into the leaf tissue, NP waveform—not probing. Waveforms S, E and F closely correlated with the the resistance of host plant against pests. With the average of probing number, the average of duration of various waveforms as indices on the various cultivars of tea plants, or with the average of duration of per waveform per probe as indices, the cluster analysis was conducted respectively. The result showed that the tested nine tea cultivars were divided into similar three groups. Then, basing the averages of duration of waveform S, E and F, and the average of durations per waveform per probe on nine cultivars within the the three groups, the resistance of nine tea cultivars to the leafhopper was evaluated, and the order, from strong to weak, ranked as Longjingchangye, Hangdan, Zhenghedabaicha, Qianmei 601, Hongyafoshuo, Zhongcha-102, Zhongcha-302, Longjing-43 and Anjibaicha. The order was consistent with the order, from small to large, of the population density of the leafhopper on the nine cultivars. Those demonstrated it to be creditable that DC-EPG technique was used to detect the resistance of tea plant to the leafhopper.Compared with probing behavior of tea green leafhopper on the non-induced tea seedlings (CK), on the tea seedlings induced by tardily releasing MeSA at 0.2, 0.4 and 0.8 mmol / L, (1) probing number (n) increased, i. e. n (ck) = 8.30±1.13, n (0.2) = 13.25±3.95, n(0.4) = 15.01±2.68, n(0.8) = 34.50±7.56; (2) non-probing waveform (NP) duration clearly enlarged, i. e. NP(ck)= 110.97±5.2 min, NP(0.2)= 128.39±6.76 min, NP(0.4)= 148.35±6.14 min, NP(0.8)= 131.94±10.75min; (3) the ingestion duration in phloem significantly degreased, i. e. E(ck)= 52.90±2.22 min, E(0.2)= 9.08±2.6 min, E(0.4)= 8.87±1.44 min, E(0.8)= 15.89±2.21 min. The inducing effect by 0.4 mmol / L was strongest among three MeSA dosages. The inducing effect from 24 h was stronger than that from 48 h. The dainty degree of the tea seedling to the leafhopper deteriorates after they are induced by MeSA, which means that the resistance of tea plants against the leafhopper is induced to a certain extent.In tea garden, the volatiles form tea plant induced by exogenous MeSA showed the clear repellent effect to tea green leafhoppers, and showed the clear attraction to the natural enemies, i e, Proplyea japonica, Harmonia axyridis, Serangium jiaponicum, spiders, parasitoids and so on. After the tea plants were induced by the exogenous MeSA, damaged by tea green leafhoppers or the volatiles of tea shoots induced by leafhopper damaging, the three types of tea shoot volatiles were determined by GC-MS, respectively. After tea shoots were induced by MeSA, the contents of Ethyl acetate, Ethanol, (E)-2-Hexenal, (E)-3,7-Dimethyl-1,3,6-octatriene, trans-Linaloloxide, cis-Linaloloxide, 1,6-Octadien-3-ol,3,7-dimethyl, alpha Farnesene, MeSA, Butanoic acid,3-proppenyl, 2,6-Octadien-1-ol, 3,7-dimethyl, Benzyl Alcohol, Phenylethyl Alcohol, 1,6,10-Dodecatrien-3-ol,3,7,11-trimethy and indole increased; simultaneously, the content of Z-3-Hexen-1-ol was decreased significantly. The fingerprints of volatiles from tea plant induced by exogenous MeSA were similar as those damaged by tea green leafhoppers.The 14 single compounds of the volatiles from tea plant induced by exogenous MeSA were respectively used as the odour source and slowly released, in which E-2-hexenal, MeSA and Benzaldehyde revealed repellence to tea green leafhopper. The spiders clearly approached Benzaldehyde, and also approached MeSA and Indole to some extent. Indole, MeSA and Geraniol showed the strong attractiveness to parasitoids; cis-3-hexen-1-yl-ester and MeSA have attractiveness to tachinidflies; Indole and MeSA showed very strong attraction to ladybeetle, Serangium japonicum. After tea plants were induced by the exogenous MeSA for 24 h at 0.2, 0.4 and 0.8 mmol / L, compared with CK, the activities of PAL in the induced leaves increased by 0.69, 1.62 and 4.73 times, the activities of LOX increased by 4.3 %, 29.0 % and 33.0 %, and H2O2 content increased by 3.4%, 10.2% and 69.7 %, respectively. The leafhopper injuring significantly induced the activities of PAL and LOX in tea leaves to ascend, and produced more H2O2, a defensive compound. After tea plants were damaged by leafhoppers12 h, the activity of PAL enzyme in tea leaves increased by 9.8 times, the activity of LOX enzyme increased by 42.6 %, and the content of H2O2 increased by 32.9 %. The inducing effect of the exogenous MeSA on some enzymes in tea leaves was similative with that of leafhopper damaging.Gene expressions differences of tea plants, which were induced by the exogenous MeSA or damaged by leafhoppers, were preliminarily studied by mRNA differential display reverse transcription PCR (DDRT-PCR). Compare with CK, 80 and 51 genes displayed the different expression by MeSA and leafhopper-damaging, respectively. After sequencing and analyzing these differentially expressing cDNA fragments, some genes were recognized to correlate with the defensive responses from plants.In summary, resulting from the induction by the exogenous MeSA, the genes correlating with defense were activated, and then the activities of the enzymes correlating with defense rose, in succession, the secondary metabolism substances with antibiosis were produced, and altered the composition of sap in the vascular bundles, which formed the effect against the feeding of the leafhopper. At the same time, the composition of the volatiles of tea shoots changed, and the ample synomones were released to attract araneids and the other natural enemies which indirectly defend the leafhopper. The induced effect of defense responses in tea plant by the exogenous MeSA was similar with that by the leafhopper damaging comparatively.
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