Effects Of Pesticide Applications On The Biochemical Properties Of Transgenic Bt Rice And The Life History Parameters Of Nilaparvata Lugens Stal (Homptera:Delphacidae)

Environmental and food safety derived from Transgenic Bt rice have caused extensive concern from academia and public because of its commercialized and large scale of plantation. The present paper selected pesticides as a stress factor, investigated the effects of pesticides on physiology and biochemistry of trans-Bt rice and the combined effects of pesticides and Bt toxicity protein on BPH. The main results are as follows:1Effects of pesticides on injury level of conventional and transgenic Bt rice.The present part examined effect of four pesticides on injury level of conventional (MH63) and transgenic Bt rice (T2A-1). Result indicated that injury level increased with an increase of pesticides concentration for both rice varieties at7days after insect release (7DAI), but no significant difference on the level was found between conventional and transgenic rice. The other three pesticides significantly influenced Injury indexes of MH63and T2A-1except for jingangmycin. For example, the injury index of MH63treated with10,20,40and80ppm triazophos increased by84.6,61.5,76.9, and6.9%and that of T2A-1increased by26.7,66.7,40and53.3%compared to untreated control, respectively; Injury indexes of MH63treated with20,40,80and160ppm chlorantraniliprole increased by123,92.3,69.2and92.3%and that of T2A-1increased by93.3,107,66.7and80%, respectively. For14DAI, pymetrozine, triazophos and chlorantraniliprole significantly influenced injury indexes of MH63and T2A-1, there was a significant difference between MH63and T2A-1. In addition, there were significant interactions between pesticide concentration and rice variety, with a maximum injury index (8.2scale) of T2A-1treated with40ppm chlorantraniliprole, increasing by64%compared to control.2Effects of pesticides on biochemical substances of MH63and T2A-1Bt toxicity protein has high control efficacy for target inset pests, especially for Lepidopteran since the release of transgenic crops. However, resistance of target pest and increase of non-target pests under high selective pressure still need to apply chemical pesticides to control non-target pests. Therefore, this study examined effects of pesticides on biochemical substances of conventional and transgenic rice and approached biochemical changes of T2A-1following pesticide applications. Results indicated that there were significant differences on soluble sugar, oxalic acid and flavonoid contents at7and14days after pesticide applications (7and14DAA) among four pesticides and between MH63and T2A-1. Changes of the substances varied with pesticide concentration and rice variety. For example, oxalic acid content of MH63and T2A-1decreased with increases of jinggangmycin and chlorantraniliprole concentrations at14DAA, but oxalic acid content of rice plants treated with pymetrozine and triazophos decreased and then increased. Soluble sugar and flavonoid contents of T2A-1treated with jinggangmycin, pymetrozine and chlorantraniliprole were significantly higher than those of MH63, but oxalic acid content was significantly lower than that of MH63.3Effects of pesticides on Nilaparvata lugens Stal (Homptera:Delphacidae) feeding on MH63and T2A-1Effect of transgenic Bt rice on non-target pests are an important aspect for the evaluation of safety. However, the evaluation of effect of transgenic Bt rice on planthoppers concentrates on direct effect of the rice to planthoppers. Effect of pesticides on planthoppers via the rice has not been understood until date. The present experiment constructed life table of laboratory population of N. lugens according to Pang (1992). Results showed that the number of laying-egg of females on T2A-1was significantly higher than that on MH63under without pesticide applications. Adult emergence rate and fecundity of adult females on both MH63and T2A-1treated with pesticides increased compared untreated control, of which triazophos significantly stimulated fecundity of N. lugens. Nymph numbers of next generation and population trend index on T2A-1treated with10ppm triazophos were significantly higher than those on MH63. Hatchability of eggs on MH63treated with jinggangmycin and chlorantraniliprole was significantly higher than that on T2A-1. These findings indicated that applications of some of pesticides on T2A-1will induce resurgence of N. lugens.4Effects of pesticides on Bt toxicity protein content of transgenic rice and its mechanismsEffect of Bt toxicity protein on ecological environment is another aspect of safety evaluation. Synthesis and expression level of Bt toxicity protein in plants are influenced by many factors. Results showed that toxicity protein content (TPC) at the seedling stage following the four pesticide applications significantly increased, especially with maximum increase for low concentration treatments. In contrast, TPC at the tillering and booting stages significantly decreased for pesticide applications. However, no impact of pesticides on TPC at the heading stage was found. In addition, the present experiment investigated effect of pesticides on the enzymes related to the synthesis of Bt toxicity protein. Results demonstrated that there was a positive correlation between and TPC and GOT or GPT activity and soluble protein. GOT and GPT activity, free ammonia acids and soluble protein of insecticide-treated T2A-1decreased significantly, indicating that pesticides interfered the synthesis of Bt toxicity protein through effects on GOT, GPT, free ammonia acids and soluble protein.