Effect Of Transgenic Cotton Cultivars On Sylepta Derogata Fabricius And Its Main Natural Enemies

The resistance of three transgenic cottons (GK12、Nucotn33B and SGK321) to Sylepta derogata (Lepidoptera:Pyralididae) was assessed in the laboratory; and the population dynamics of S. derogata and its dominant natural enemies were studied and the effects of transgenic cottons on its larval parasitoid Apanteles derogatae Watanabe (Hymenoptera:Braconidae) and its larval predator Chrysoperla carnea Stephens (Neuroptera:Chrysopidae) were also evaluated. The transmission of Bt protein from S. derogata to the parasitoid or predator in food chain was studied using Enzyme Linked Immunosorbent Assay (ELISA). The results were as following:1. The field investigation of population dynamics S. derogata and it parasitoids and predators showed that there were no significant differences in population of predators of S. derogata among the six cotton varieties, But the larvae population of S. derogata and population of A. derogatae in fields of Nucotn33B and SGK321were significantly lower than those in the corresponding controls. There were no significant difference in population of S. derogata and A. derogatae of GK12, compared with those in SM3.2. The resistance of three transgenic cottons to S. derogata was determinined by in the laboratory. The results showed that the three transgenic cottons were all of better resistant to the2nd、3rd and4th instar larvae of S. derogata than their corresponding controls, respectively; And larvae mortality was more than90%when fed with three transgenic cotton varieties6d, Therefore, transgenic cottons can effectively control S. derogata and reduce its damage to cotton.3. There were some effects on the egg-lavae duration, pupal weight, pupal period, emergence rate, adult weight and longevity of A. derogatae when the parasitized host larvae fed on the GK12leaves for24h, but no significant compared with those of A. derogatae fed on the parasitized host larvae in SM3. The parasitoid offspring developed more slowly, the rate of emergence decreased by12.99%, the adult weight reduced0.24mg and the adult longevity reduced2.1d when the parasitized host larvae fed on the Nucotn33B leaves for24h, compared with those for the non-Bt treatment (line33), but there was no significant difference in weight of pupal and abnormal pupal rate compared with the control. As to SGK321, there was more significant difference in the egg-larvae duration (0.5d delay), adult longevity (2.3d decrease) of A. derogatae compared with the control (Shiyuan321); Although there were some effects on, the the pupal and adult weight, cocoon duration and emergence rate were not significantly different with those of the control. The longevity of female (11.8d and10.7d)and male (9.3d and10.7d) parasitoids was not significantly affected when newly emerging A. derogatae fed on honey solutions containing two different concentration of Cry1Ac protoxin (2.5,25μg/g), and it revealed that Bt had no direct effects on parasitoid.4. Laboratory study was performed to investigate whether predation behavior and growth of C. carnea were affected by transgenic cottons. The predating functional response of C. carnea was conducted using S. derogata larvae that were reared on the transgenic cotton in laboratory. The results showed that the predating number of C. carnea to the preys was significantly more than that of conrol cotton (SM3), the predating functional response was in accord with the Holling Ⅱ, the maximum predating number of C. carnea was higher, the handling time was shorter, and the parameter of functional response (the attacking rate) was higher than those of the control, respectively. Larvae of S. derogata, preys for C. carnea, were fed on transgenic cottons (GK12, Nucotn33B, SGK321) or conventional cotton (SM3) respectively. The results showed that the larvae duration of C. carnea was delayed0.26d,0.15d and0.25d and significantly longer compared to that of lavae fed on the control; there were also some effects on the mortality of larvae (2.8%,8.2%and8.8%increse) and cocoon weight (0.50,0.21and0.12mg decrease) and emergence rate (10.1%,0.7%and2.2%decrease), but no significant difference with the control.5. Bt(Bacillus thurngiensis Berliner) insecticide protein in the larvae of S. derogata, the old larvae of C. carnea and A. derogatae was detected and quantified by ELISA. The results showed that Bt protein could be transferred to C. carnea via its prey S. derogata, but there was no Bt protein detected in the parasitoid A. derogatae.