Study On The Resistance Of Camellia Sinensis Induced By BTH And BABA To Ectropis Oblique

Tea scele(Ectropis obliqua Prout) is one of the most destructive pests on tea plants(Camellia sinensis), causing wide-spread damage and large economic losses in tea production. At present, controlling of E. obliqua is relied mainly on the application of varieties chemical pestcide including chlordane, organophosphorus insecticide, viral insect pathogene and so on, which leading to the pest resistance to insecticide and high pesticide residues in the tea plantation, at the same time environment polution have gone up. Thus developing new methods instead of using pesticides for controlling of E. obliqua come to urgently needed. Recently,Benzothiadiazole (BTH) as well as β-aminobutyric acid (BABA) was report can be used as a new type of exogenous, inducing defence substances ocurred and enzyme activiate,and sequencely strengthening immunity ability of the plant. Therefore, using BTH and BABA to improve the resistance of tea plant against E. obliqua may reduce the pesticides use, so it showed a broad development prospects in the pest control of tea gardens.In the present dissertation, tea variety of’longjing 43’was used for testing, BTH and BABA with different concentrations was sprayed on the tea plant, then 2nd geometrid larvae of E. obliqua was fed on the treated leaves of tea plants, the developmental duration,weight of larva,weight of pupa,survival rate,pupation rate,eclosion rate,feeding amount of each instar larvae and the activities of the chymotrypsin-like enzyme activities, high alkaline trypsin-like enzyme.low alkaline trypsin-like enzyme in their midgut of geometrid Ectropis obliqua larvae were studied.The length and weight of tea shoots, and the content of water, dry matter, polyphenols, amino acids, caffeine, catechins, soluble sugar, soluble protein were also tested. The activity of PPO, PAL, POD of tea leaves after treated 6 h,24 h,48 h,72 h and the relative expression PPO,PAL genes were determinedBased on the comprehensive analysis of the data got in our experiments, direct and indirect mechanism of tea plant induced resistance by BTH and BABA was inferred.The main findings of the dissertation were as follows:(1) Effect of BTH and BAB A on the growth of Ectropis obliqua Warren larve2nd geometrid larvae of Ectropis oblique was fed on the leaves of tea plants treatment with BTH and BABA, the developmental duration, weight of larvae, weight of pupa, survival rate, pupation rate, eclosion rate, leaf volume of each instar larvae were determined. Results showed that:(a) Differences in the Ectropis obliqua Prout larvae periods with different concentrations of BTH and BABA were not significant. Both 25 mg·L-1 BTH and 200 mg·L-1 BABA had no effect on 3rd instar larvae, so did 50 mg·L-1 BTH and 300 mg·L-1 BABA on 5th instar.Though larvae periods increased with other treatments, only a difference of 1 to 2 days. The survival rate, pupation rate, eclosion rate reduced The longer the periods. The shorter the survival rate, pupation rate, eclosion rate, (c) There was little difference in 3rd instar larval body weight. Compared with control,4th and 5th instar larval body weight significantly decreased with 75 mg·L-1 BTH and 400 mg·L-1 BABA. The pupal weight lower than the control, and increased firstly and then declined with the concentration of BTH, BABA increasing, (d) Compared to the control, the leaf volume increased of 3rd instar larvae and decreased of 4th instar larvae.There was no significant difference at 5th instar.(2) Effect of BTH and BABA on the midgut proteinase activity of geometrid Ectropis obliqua larvaeThe activities of the chymotrypsin-like enzyme, high alkaline trypsin-like enzyme, low alkaline trypsin-like enzyme in their midgut were studied. The results showed that the activities of the chymotrypsin-like enzyme and low alkaline trypsin-like enzyme of 3rd,5th instar larvae were significantly inhibited, but the activity of high alkaline trypsin-like enzyme was unaffected with BABA, leading to imbalance between different types of proteinase activity in the midgut of the larvae.(3) The effect of BTH and BABA on the physical characteristics of shoots and chemical compositions of tea leavesThe length and weight of shoots, the content of water, dry matter, polyphenols, amino acids, caffeine, catechins, soluble sugar, soluble protein were tested. The results came out as follows:(a) The length and weight of shoots, the content of water and dry matter of tea leaves were not significantly affected. (b) Both BTH and BABA improved contents of polyphenols, amino acids, caffeine, catechins, soluble protein, and reduced the content of soluble sugar BTH better than BABA, overall.(4) The effect of BTH and BABA on the activity of PPO, PAL enzymes of tea leavesThe activities of PPO, PAL and POD enzymes increased after 6 h PPO activity was higher than the control and peaked at 72 h. The activity of PAL was lower at 24 h and higher at 48 h than the control, and peaked at different times with different treatments. PPO activity peaked at 24 h except 300 mg·L-1 BABA.(5) The effect of BTH and BABA on the relative expression of PPO, PAL genesThe relative expression of PPO and PAL genes was evaluated by real-time RT-PCR technique. Compared to control,75 mg·L-1 BTH and 400 mg·L-1 BABA increased the expression of PPO gene with 1.42,2.72 times, respectively. PAL gene’s expression increased with different treatments except 25 mg·L-1 BTH and 200 mg·L-1 BABA. It was supposed that low concentrations of these two chemical inducers.