【作者】 李娜；

【导师】 翟保平；

【作者基本信息】 南京农业大学 ， 农业昆虫与害虫防治， 2004， 硕士

【摘要】 棉铃虫(Helicoverpa armigera)属鳞翅目夜蛾科，广泛分布于南北纬50度之间，是一种世界范围的重要农业害虫。近年来，转Bt基因棉以其良好的抗虫性，在降低生产成本，减少农药污染等方面都发挥了重要作用，因此得到了广泛的应用。然而，随着转Bt基因棉的大规模商业化释放，其潜在的生态风险也越来越受到重视，主要集中在对靶标生物抗性的产生以及对天敌昆虫安全性评估两方面。 以往用于检测棉铃虫抗性产生及转基因棉对天敌昆虫安全性的方法都需要花费大量的人力和金钱，是否存在一种简便、快捷，易操作、花费低，但同时又对环境压力十分灵敏的生物指标，能够对生物所受到这种不利影响作出指示呢?波动性不对称(Fluctuating asymmetry,FA)被许多国外学者认为是最有希望能够成为这种环境压力的生态指标。 本文针对转Bt基因棉压力下棉铃虫及其天敌的FA开展研究，探索了以FA作为转基因棉安全性指标的可能性。主要研究结果如下： 一、靶标害虫的FA 在实验室内，利用Bt棉叶片饲喂法对棉铃虫幼虫进行了连续13代的筛选，逐代记录种群的各适合度参数，同时选择了前足腿节、翅脉L1、后翅翅长这三个特征作为FA的研究对象。适合度的研究结果表明，转Bt基因棉对棉铃虫的生长发育产生了诸多不利影响：与对照种群相比，幼虫的存活率显著降低、发育历期延长、雌成虫产卵量减少、卵的孵化率降低以及成虫寿命缩短。虽然在连续13代的筛选过程中，幼虫存活率表现出逐渐增加的趋势，但是雌虫产卵量、卵孵化率与成虫寿命仍然呈下降趋势；对照种群在连续12代的饲养过程中幼虫的存活率略有上升，而适合度参数却略微下降，但并不如处理种群明显。对FA的研究结果表明，除对照种群中第一代的L1未表现出FA外，其它各特征在不同种群与世代中都表现出FA。无论在处理种群还是对照种群中，随着筛选代数的增加，前足腿节、L1、后翅翅长的FA值均出现下降的趋势，将其与适合度各参数进行相关性分析后发现，处理种群中，后翅的FA4值与种群的存活率间存在显著的负相关关系(r=-0.64，p＜0.05)；在对照种群中，后翅翅长的FA3和FA4值与存活率间同样也存在显著的负相关关系(r=-0.61，p＜0.05；r=-0.63，p＜0.05)。据此，可以认为FA水平的变化能够反映出棉铃虫种群对转基因棉压力存在转Bt基因棉压力下靶标害虫及其大敌的波动性不对称适应性的趋势。对Bt毒蛋白及Bt杀虫剂高杭品系棉铃虫的FA研究发现，其与敏感品系间无显著差异。同时，对照种群在个体水平上雄成虫翅脉L1的不对称与幼虫发育历期呈极显著的正相关关系，而与蛹重呈极显著的负相关关系。 对转基因棉筛选了8代后的棉铃虫种群，牙J用亲子回归系数法估算了棉铃虫前足腿节与翅脉L1的FA与其长度的狭义遗传力矿，结果表明:前足腿节与翅脉的FA均不表现出遗传效应，即尸的值与零的差异不显著;但这两个特征的大小具有显著的遗传力。结合上面的研究结果，得出FA是反映转基因棉的选择压力对棉铃虫发育稳定性影响的理想指标，但前足腿节与翅脉的FA不适于作为指示棉铃虫遗传质量的指标。 2002年上半年在我国北方棉区选取了有1一5年Bt棉种植史的4省13个县、市作为田间棉铃虫种群FA研究的虫源地:河南省的郸城、新乡、安阳、民权，河北省的辛集、大成、抚宁、饶阳、任丘，山东省的汉上和巨野，以及江苏省的享宁和丰县。矛){用黑光灯诱蛾法采集了各点棉铃虫上灯蛾，在实验室内测定了各点成虫后足腿节的FA。结果表明，除河北省辛集外，十二个采集地的棉铃虫后足腿节均表现出FA;相关性分析发现，各采集点的FA值与Bt棉的种植年代间存在着显著的负相关关系(:一0.77，P<o.05)，显示出棉铃虫自然种群对Bt棉的适应性随着Bt棉种植时间延长而渐增的趋势。 在研究转基因棉压力下棉铃虫各特征FA的同时，我们在室内种群中发现前翅副室与翅脉存在多种不同类型的变异:副室端部不能封闭;中室下底Cul:与Cu】b间的一段翅脉变异为两条;Cul。上多出一条崎形的附加翅脉;Cula与Culb这两条翅脉的中部多出一条肘横脉;副室的前方，由中室基部发出的分径脉又形成另一个封闭的翅室。同时还发现，取食转基因棉的种群中变异个体的数量要多于取食常规棉的数量。结合其他相关报道，认为极端环境压力可能是诱导变异产生的原因之一。二、捕食性与寄生性天敌的FA 以取食转Bt基因棉上的蚜虫(APhis 905卿11)的异色瓢虫(Harmonia axxri苗s)作为研究对象，考察了其适合度、功能反应以及后翅的FA值与取食常规棉上蚜虫的对照种群间的差异。结果表明，取食了转Bt基因棉上的蚜虫后对瓢虫的适合度各参数及各虫龄的捕食功能反应均无不良影响;处理种群与对照种群的后翅均表现出FA，前者的FA值略高于后者，但经F检验后发现差异不显著(F(28，19)=1 .2119，P>0.05)。转Bt基因棉压力下靶标害虫及其天敌的波动性不对称·摘要说明，FA能够正确反映转基因棉对异色瓢虫的影响。 再以棉铃虫体内寄生蜂斑痣悬茧蜂(MetooruspulchricoI’nis)为研究对象，考察了其在转Bt基因棉压力下的适合度及FA，及两者在个体水?更多还原

【Abstract】 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更多还原