Risk Assessment Of Bt Cry1Ah Gene Corn On Honeybee

The honeybee is widely recognized as a beneficial insect of agronomic, ecological, and scientific importance. It produces commercially valuable products (honey, pollen, royal jelly, propolis, and wax) and plays a major role in crop pollination. Insecticide is one of causes of honeybee colony disorder in the world. Transgenic insect-resistant crop is one of the possible ways forward with the aim of combining higher yield and quality with environmentally friendly agronomic practices. Bt crop truly reduces insecticide applications, then Bt crops may increase the abundance of honeybees. The cry1Ah gene was one of the novel insecticidal genes cloned from Bacillus thuringiensis isolate BT8 which exhibited high toxicity against lepidopteran larvae. Cry1Ah protein showed higher toxicity to Asian corn borer (Ostrinia furnacalis) than that of any other cry1A genes. The cry1Ah gene was a candidate gene for insect resistant transgenic corn research. Assessment of impacts on honeybee is an essential part of the risk assessment process for Bt cry1Ah gene corn.The objective of this study was to assess effects of various concentrations of the Cry1Ah toxin in laboratory condition and Bt corn pollen under field cage conditions on honeybees. The effects of Cry1Ah toxin on wax moth (Galleria mellonella) and honeybees with parasitical mites were also tested. The lethal and sublethal effects of chemical insecticides on honeybees were assessed as positive reference. The results were as follows:1. We conducted feeding trials in a laboratory setting to test for possible adverse effects of different concentrations (10000 ng/ml, 10 ng/ml and 1 ng/ml) of microbially produced Cry1Ah toxin on survival, pollen consumption and hypopharyngeal gland mass of Apis mellifera ligustica and Apis cerana cerana. There were no significant differences in mortalities of Apis mellifera ligustica or Apis cerana cerana among groups fed sugar syrup with or without Cry1Ah toxin within 24, 48 or 72h. Adverse effects of Cry1Ah toxin on survival of Apis mellifera ligustica and Apis cerana cerana were not observed. No significant differences were found in the longevity of Apis mellifera ligustica fed sugar syrup with Cry1Ah toxin compared with control. In experiments with Apis cerana cerana fed Cry1Ah toxin, only a concentration of 10ng/ml Cry1Ah toxin resulted in a significantly longer longevity compared with the control. No differences were detected for pollen consumption and hypopharyngeal gland mass of Apis mellifera ligustica and Apis cerana cerana.2. We dissociated neurons from brains of bee workers. This preparation resulted in a large number of isolated viable neurons. Effect of Bt toxin on the excitability of the isolated neurons were observed by the whole-cell configuration of the patch-clamp technique. The results showed that Bt toxin (10ng/ml and 100ng/ml) did not affect excitability of the isolated neurons, because current threshold did not change significantly.3. The effects of dietary transgenic Bt corn pollen on honeybee worker larvae of Apis mellifera ligustica and Apis cerana cerana were examined. We measured cap rate, emergence rate, success rate of development, and immature stage after 4-6-day-old larvae were fed various pollens (Bt cry1Ah gene corn pollen, non-Bt corn pollen, mixed bee pollen and control). There were no significant differences in all the parameters tested among treatments. Our studies suggest that transgenic Bt corn pollen does not pose a threat to honeybee larval development. The sublethal effects of chemical insecticides bifenthrin and deltamethrin on honeybees were assessed as positive reference. Effects of two pesticides at the sub-lethal concentration on honeybees were examined with the feeding method. It was shown that both bifenthrin and deltamethrin significantly decreased the rate for bee to develop to adulthood and increased their immature periods.4. Honeybee could be exposed to insecticidal proteins from transgenic plants via pollen. Assessment of impacts on honeybee is an essential part of the risk assessment process for Bt corn. A field trial was conducted to evaluate the effect of transgenic Bt cry1Ah gene corn on honeybee, Apis mellifera ligustica. Colonies of honeybees were moved to Bt or non-Bt corn fields during bloom and then sampled for survival, development and behavior. No differences in immature stages, workers survival, bee body weight, hypopharyngeal glands weight, colony performance, foraging activity and olfactory learning abilities were detected between colonies placed in non-Bt corn fields and those in Bt corn fields. Results from this study suggest that transgenic Bt cry1Ah gene corn pollen does not have adverse effects on Apis mellifera ligustica.5. The effects of dietary Bt Cry1Ah toxin (1 ng/ml,10 ng/ml and 10000 ng/ml) on honeybee workers parasited by Varroa destructor were examined. There were no significant differences in mortality tested between workers fed Bt Cry1Ah toxin and control. We also evaluated Bt Cry1Ah toxin as a potential control for wax moth larvae in a laboratory study. We fed wax moth larvae three concentration of Cry1Ah toxin: 1 ng/g,10 ng/g and 10000 ng/g. We found that the mortality of larvae fed artificial diet containing Cry1Ah toxin was significantly greater than the mortality of larvae fed artificial diet without Cry1Ah toxin. Our studies suggest that transgenic Bt corn pollen does not pose a threat to honey bee larval development and has the potential to serve as an alternative control for wax moth.