| Based on three transgenic cottons (GK22, SK103 and ZK310) and two non-transgenic, parent's cottons (SM3 and SM12) as the control, we studied the population dynamics of Aphis gossypii Glover in different cotton fields and the relationship between the population dynamics and different cottons types. The results were as following:By conducting the life table of natural population across three continuous generations of A. gossypii in Yangzhou city, Jiangsu Province in 2003, we found combined population trend index (I) of three continuous generations of A. gossypii in GK22 field was 5.40, 1.41 times more than that in SM3 field, the population trend index in SK103 and ZK310 field were 49.54 % and 65.79 % larger than that in SM12 field respectively. The results showed the increase rate of the population of A. gossypii in the transgenic cotton fields were larger than that in the control fields. By analyzing exclusive index of population control (EIPC), the results showed that rainfall was the biggest influence factor on the population increase of A. gossypii with EIPC from 1.71 to 2.00, EIPC of predation was the second, and those of disease, parasitism, natural death and others were in proper order. Comparing EIPC of each factor among different cottons, it pointed out the parasitism rate of parasitoids in transgenic cotton fields was less than that in the control fields respectively. And the effects of predation, rainfall and other factors were different among these cotton fields.By studying the population dynamics from greenhouse population of A. gossypii, we found there were some differences among survival rate, development duration, reproductive rate and some life parameters such as net reproduction rate, mean generation and finite rate of increase of the population on the transgenic cottons and the control cottons. The intrinsic rate of increase of A. gossypii on GK22 and SM3 were 0.4460 and 0.4015 respectively, and that on SK103, ZK310 and SM12 were 0.4434, 0.4371 and 0.4077. The results indicated three transgenic cottons were more apt for the development of A. gossypii than the corresponding control.Meanwhile, daily average honeydew secretion amount of A. gossypii feeding on SM3 and GK22 were 0.4324 mg and 0.2557 mg was difference at 0.01 level by statistical analyses, and those on SM12 and SK103 were 0.3002 mg and 0.2322 mg without significant difference, and that on ZK310 was 0.2098 mg with the difference at 0.05 level with that on SM12. In addition, there were some differences among the amounts of all free amino acids, soluble sugar, sucrose of honeydew from A. gossypii feeding on transgenic cottons and the control cottons. The results showed the transgenic cottons had affected the amount of honeydew and its compositions secreted by A. gossypii.The tannic acid was found in cotton leaves. And the content of nutrients such as each free amino acid, fructose, mamnose, trehalose, glucose, sucrose, maltose, and secondary substances such as condensed tannin, tannic acid, gossypol were different between transgenic cottons and the control cottons. The results showed the contents of nutrients and secondary substances of cottons had been affected due to the resistant gene's insert.The effect of four bio-chemicals such as gossypol, tannic acid, proline and tyrosine on population development of A. gossypii was assessed by feedback rearing at artificial diets with these substances above-mentioned of different contents. The results showed A. gossypii died in a short time when the additional concentration of every biochemical was over 200ppm and also had no reproduction. As the content was 100ppm or 50ppm, secondary substances tannic acid and gossypol had great adverse effects on the survival rate, capacity of reproduction and population development of A. gossypii. And when the additional content was 100ppm, 50ppm or 25ppm, proline and tyrosine had some negative effects on the population development of A. gossypii. However, without proline or tyrosine intrinsic rate of increase of A. gossypii was also less than that of the control. I... |
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