| The cotton bollworm, Helicoverpa ormigera(Lepidoptera: Noctuidae), is a worldwide pest. Bt-transgenic cotton that express insecticidal proteins from Bacillus thuringiensis is rapidly developing as a novel control measure for the cotton bollworm. As the large scale commercial released of Bt-transgenic cotton, the possible ecological risks focused on the evolution of pest resistance to Bt cotton and the effects to target and non-target insects have received more and more concern and have been assessed by various approaches. But the traditional methods to monitoring the bio-safety of transgenic crops (say life-table or bioassay) are usually time-consuming, laborious and costly, so we should try to find a simple, easy and sensitive measure to get early-prediction of the trade-off of population status or environmental pressure. Fluctuating asymmetry, small random differences between left and right and with a low level of heritability, is advocated by some scientists as an "early warning system" for stress-mediated changes in developmental instability.In this paper, we explored the possibilities that using the fluctuating asymmetry in target pest and natural enemies under the stress of transgenic cottons a simple and sensitive indicator to monitoring the ecological safety of Bt-transgenic cotton.1. FA in the target pestIn the laboratory, the Bt-transgenic cotton leaves were used to feed cotton bollworm (CB) larva for 13 generations under resistance monitoring. The fitness and the FA in three traits in every generation were observed. The results show that there were significantly fewer eggs per female, lower egg hatchability, shorter adult longevity, and longer duration of larva in treatment population than that in control population. The rate of larva survival had an ascending tendency when CB continuously feed Bt-cotton and conventional cotton for 13 generations, but the fitness had a reverse tendency. To test the fluctuating asymmetry (FA) in fore femur, special vein L1 and hind wing under the stress and control, the resultshow that all traits except for L1 in first generation of control population demonstrated FA, and a majority of FA values were larger in treatment compare to those in control. We also found there was a tendency for the level of FA to decrease both in treatment and control population. We also tested if there was a relationship between FA and any fitness components at the population level. Significantly negative relationship was found between the FA in hind wing and the rate of larva survival in stress treatment (r=-0.64, p<0.05 ) , there is also a negative relationship in control too. According to these results, we believe FA can indicate the adaptation of lab population of CB to Bt cotton. We also tested the FA in CB with high resistance to Bt-protein and Bt-insecticide, the result shown, there is no significant difference between resistant strain and susceptive strain. At the individual level, the FA in L1 of the control population was significant positively related to larval duration and inversely related to pupa weight.Fluctuating asymmetry (FA) has been proposed as a tool to measure levels of stress experienced by populations of organisms during development, so it is important that variation in FA levels is due to environmental variation and not genetic variation among populations and families. So we assess the narrow-sense heritability (h2) of FA and size in fore femur and cross vein of laboratory population CB using parent-offspring regressions after selected by Bt-cotton for 8 generations. The result show, FA was not significantly heritable for any of the individual traits, that is to say that heritability of FA was low under laboratory conditions; on the other hand, the length of two traits have significant levels of additive genetic variance. According with those results, we considered that FA can be used as an indicator of Bt stress, however, FA in fore femur and L1 may therefore be a poor indicator of genetic quality in CB.After having studied the FA in laborator...
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