| Micromelalopha troglodyta (Lepidoptera, Notodontidae) is definitely the most important pest of poplar plantation in Jiangsu Province, which is too difficult to control. The problem of the pest could not be resolved ultimately by using chemical technique currently, and the exclusive use of chemical pesticides results in build-up of pesticides resistance rapidly. Therefore, it is urgently needed to find the new methods and technologies of the pest control. Genetic engineering by inserting resistant genes into plant genome, which confers insect resistance on the plant, has already been an effective approach of pest control. Four kinds of transgenic poplars (NL80106) mediated by Agrobacterium tumefaciens, 130 clones in total, were obtained in the Laboratory of Forest Genetics and Gene Engineering in Nanjing Forestry University, and applied into field experiments. The materials for this testing were the progeny of transgenic poplars (NL80106) planted in field. This research selected 11 clones expressed insecticidal activity to M. troglodyte from 130 clones and mainly discussed the spatio-temporal characteristics of the insecticidal capacity that eleven transgenic poplars expressed, the insecticidal activity on different instar larvae and the restriction to the growth of the larvae by using bioassay. The insecticidal mechanism of transgenic poplars was discussed by determining the influence of transgenic poplars on detoxification enzyme and protective enzyme in the midgut and haemolymph of larvae. Moreover, the expression of insecticidal protein in the transgenic poplars was also examined in this paper. Main results are listed as following: 1. M. troglodyta has five generations a year in Xuzhou district, Jiangsu province and overwinters as pupa. The first generation is the accumulating stage of the population. The second generation is the population growth stage. The third and fourth generations are the outbreak stage. The population dynamics are affected by the temperature, humidity, rainfall, natural enemy, forest structure, and field cultivation factors. 2. The methods of breeding of M. troglodyte in the laboratory and the evaluation of the insecticidal capacity of transgenic poplars were established in the paper. Insecticidal capacity of transgenic poplars was evaluated by integrated factors that included experimental insects, spatio-temporal dynamics of the insecticidal capacity, the influence on the growth of larvae and the data's procession and analysis. These methods could be used as references for the biological evaluation on the insect-resistance of transgenic poplars. 3. Transgenic poplars could greatly decrease quantity of the larvae under the controlled and field conditions. Among the eleven transgenic clones with Bt Cry1Aa gene, CpTI gene, AaIT gene and Bt + CpTI genes, 4 clones, FB56, FC5, T22, D18, were provided with superior insecticidal capacity. The revised mortality of 1st instar larvae reached 84.3%, 98.0%, 91.1% and 90.2% respectively. The insecticidal capacity of transgenic poplars assumed seasonal rhythm. When 1st instar larvae were fed with leaves of four transgenic poplars for 12 days, the highest revised mortality occurred in the early stage of growth (June). The insecticidal activity of transgenic poplars decreased in mid stage (July and August) and raised again in later stage (September). The insecticidal capacity of transgenic poplar clone (D18) expressing both Bt and CpTI genes was higher than that expressing Bt only in the early stage. The insecticidal activity of transgenic poplars expressed the evident spatial dynamics. The insecticidal capacity of the upper leaves of transgenic poplars was significantly higher than the lower and central leaves. 4. The sensitivity of the various instar larvae of M. troglodyta to transgenic poplars with Bt gene, CpTI gene and Bt + CpTI genes was different. The revised mortality of 1st~3rd larvae fed with leaves of transgenic poplars for six days had significant differences with CK, while the revised mortality of 4th~5th larvae had no significant difference. Four transgenic poplars greatly inhibited the development of larvae. The feeding, weight and the growth rate of larvae decreased greatly. Most of them couldn't pupate after feeding with the leaves. Some of them died in the larvae stage. A few of larvae fed with the transgenic poplars could pupate at the end of the experiment. It seemed that transgenic poplars had little effect on the feeding and the growth rate. 5. The larvae of M. troglodyta were fed with leaves of transgenic poplars with Bt gene, CpTI gene and Bt + CpTI genes, the activity of Esterase in the midgut of larvae raised in the earlier stage, but restricted later. When the larvae were treated with leaves of transgenic poplars expressing Bt gene, CpTI gene and Bt + CpTI genes respectively, the corresponding highest restrictive stage was 48, 24, 12 hours. The restrictive efficiency of the clone expressing Bt and CpTI was superior to that expressing Bt alone. The restriction of the poplars carrying single gene to carboxyleterase in the midgut of larvae was not notable, but the plants carrying two kinds of genes could restrain the activity of the carboxyleterase significantly. The transgenic poplars disturbed the insect regular metabolism by restraining the activity of Esterase and Carboxyleterase in the midgut of larvae, then killed the pests. 6. The larvae of M. troglodyta were fed with transgenic poplar leaves with Bt gene and CpTI gene for 24 hours, the activity of SOD in the midgut of larvae was raised by 41.7%, 55.7% respectively, which had significant differences with CK. But the transgenic poplars expressing two kinds of genes had no significant difference with CK. After feeding 24 hours with Bt gene and CpTI gene poplars, the activity of CAT was restrained significantly, but the restraining ability was not strong after 36 hours. CAT activity was controlled significantly after treating with transgenic poplars carrying two kinds of genes. Three transgenic poplars all restrained the activity of POD greatly after 36 hours procession. Thus, the transgenic poplars could disturb the dynamic balance of SOD, CAT and POD in the midgut of larvae, which was the one of acting mechanisms. 7. PCR analysis of the progeny of transgenic poplars planted in field showed that Btpeculiar fragments all can be examined in five Bt poplars and four Bt + CpTI poplars, CpTI peculiar fragments were also examined in five CpTI poplars. The leaves from 12 transgenic poplars were analyzed by ELISA, and it showed that among the transgenic poplar clones with two kinds of genes the Bt insecticidal protein of clone D18 was greatest, which was 0.090% of total plant soluble protein. Among the transgenic poplar clones with Bt gene, the Bt insecticidal protein of FB51 was greatest, which was 0.036% of total plant soluble protein. In the transgenic poplar's leaves, the temporal dynamics of insecticidal protein and insecticidal activity were the same. This research selected 11 transgenic insect-resistant poplar clones, and they showed high insecticidal effect on M. troglodyta. The insecticidal capacity was of the evident spatio-temporal dynamics. In the initial stage of the poplars, the insecticidal capacity was greatly, and it could control the increase of the pest's population number effectively. After September, the great insecticidal capacity could decrease the overwinter base of the insect. The spatio-temporal dynamic characteristics on the insecticidal capacity of transgenic poplars was benefit for the insect control. At present, the management of M. troglodyta was still very hard. The transgenic poplars (NL80106) will be an effective method to the comprehensive administration of M. troglodyta.
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