转Bt棉主茎叶Cry1Ab/c蛋白含量的时空分布分析

为明确M-49和X-37转基因棉Cry1Ab/c蛋白在主茎叶片的时空分布,采用酶联免疫法(ELISA)对主茎叶片的Cry1Ab/c蛋白含量进行检测,并利用考马斯亮蓝法检测叶片水溶性总蛋白含量。结果表明:X-37主茎叶片Cry1Ab/c蛋白整体含量高于M-49;两种转Bt棉主茎叶的Cry1Ab/c蛋白含量由顶端向底层逐渐增加,现蕾期(6月3日)和初花期(6月27日)底层叶片Cry1Ab/c蛋白含量显著高于顶端叶片;花铃期(8月6日)和铃期(8月26日)中上部叶片Cry1Ab/c蛋白含量均无明显差异。另外,在初花期(6月27日)主茎上部叶片的Cry1Ab/c蛋白与水溶性总蛋白比显著高于中下部叶片。总体上,两种转Bt棉主茎叶片Cry1Ab/c蛋白叶片含量分布由下至上逐渐减少,随生育期的推进呈先增后降,在初花期的上部叶片Cry1Ab/c蛋白与水溶总性蛋白比变化较其他生育期明显。     

转Cry1Ac+Cry2Ab基因棉花主要生化物质含量变化及其对棉田昆虫的影响

【目的】新型转基因棉花在进入大规模商业化应用前,需对其生态环境安全性进行评价;同时,经基因改造的新型转基因抗虫棉花可能影响抗虫棉的次生代谢,进而导致一些综合的生态学效应,致使棉花生理上发生改变,这也是转基因植物安全性评价研究的重要内容。【方法】比较了不同关键时期新型转Cry1Ac+Cry2Ab基因棉花与转Cry1Ac基因棉花和非转基因棉花叶片的鲜重、干重和干鲜比、主要酶[超氧化物歧化酶(SOD)、过氧化氢酶(CAT)、过氧化物酶(POD)、抗坏血酸过氧化物酶(APX)和谷胱甘肽还原酶(GR)]活性、营养物质(蛋白质、氨态氮、脯氨酸和可溶性糖)和次生代谢产物(棉酚和单宁)含量的差异及其对棉田不同昆虫营养层昆虫个体总数和物种数的影响。【结果】棉花生长的蕾期、花期和花铃期,转Cry1Ac+Cry2Ab基因棉花、转Cry1Ac基因棉花和非转基因棉花叶片的鲜重、干重和干鲜比呈先升高后降低的趋势;SOD和POD活性在花铃期明显升高,CAT、APX和GR活性无显著变化;蛋白质、氨态氮含量无明显变化,脯氨酸和可溶性糖含量均表现为先升高后下降的趋势;棉酚含量在3个时期无显著变化,而单宁含量呈逐渐升高的趋势。3种棉花叶片中干物质积累、主要酶活性、营养物质和次生代谢产物含量均无显著差异;单株大铃数表现为转Cry1Ac+Cry2Ab基因棉花转Cry1Ac基因棉花非转基因棉花,小铃数则表现为转Cry1Ac基因棉花Cry1Ac+Cry2Ab基因棉花非转基因棉花;昆虫群落和害虫亚群落的昆虫个体总数均表现为转Cry1Ac+Cry2Ab基因棉田转Cry1Ac基因棉田非转基因棉田,天敌亚群落昆虫个体总数无显著变化;3种棉田中昆虫群落、害虫亚群落和天敌亚群落的物种数均未发生显著变化。【结论】转Cry1Ac+Cry2Ab基因棉花叶片干物质积累、产量性状、生化物质含量、酶活性在不同生长期表现不同,但上述参数在3种棉花之间无显著差异;且转Cry1Ac+Cry2Ab基因棉花具有较好的抗虫性,能有效降低棉田害虫数量。     

转Cry1Ac+Cry2Ab棉花生长势及其对棉田节肢动物物种丰富度的影响

【背景】转基因棉花在商业化种植之前,必须评价其环境安全性。其中新型棉花材料的生存竞争能力和对物种丰富度的影响是评价的重要内容。【方法】以转Cry1Ac＋Cry2Ab基因棉为试验材料,转Cry1Ac棉花中棉所41和非转基因棉花中棉所49为对照品种,分别于2014年5~9月对棉花株高、主茎叶片数、叶绿素含量、比叶面积、果枝数、蕾铃数等生长参数进行比较,同时对二代、三代和四代棉铃虫发生期棉田物种丰富度进行系统调查。【结果】转Cry1Ac＋Cry2Ab棉花的生长势与转Cry1Ac棉花和非转基因棉花基本相当,没有表现出明显的竞争优势;产量构成参数在成铃和脱落等方面比非转基因棉表现出良好的优势。对棉田节肢动物物种丰富度的影响表明,转Cry1Ac＋Cry2Ab棉花对靶标害虫棉铃虫具有良好的控制效果,对主要刺吸性害虫棉蚜、棉蓟马、烟粉虱、绿盲蝽与天敌龟纹瓢虫、草间小黑蛛、草蛉和小花蝽等的种群丰富度在个别时期有所影响,但总体上与转Cry1Ac棉田和非转基因棉田没有显著性差异。【结论与意义】转Cry1Ac＋Cry2Ab棉花无竞争优势,但目标性状优势较好;对棉田节肢动物物种丰富度无明显影响。研究结果为新型转Cry1Ac＋Cry2Ab棉花对棉田环境安全方面的研究进一步补充了内容,为转基因棉花的环境安全评价提供科学数据。     

转Cry1Ac+Cry2Ab棉对棉铃虫的控制作用及对天敌捕食烟粉虱功能反应的影响

文章以转Cry1Ac基因棉(中棉所41)和常规棉(中棉所49)为对照,研究了转Cry1Ac+Cry2Ab基因棉(639020)在棉花生长的关键时期——蕾期(二代棉铃虫发生期)、花期(三代棉铃虫发生期)和花铃期(四代棉铃虫发生期)对棉铃虫的控制作用,同时研究了639020棉田主要捕食性天敌(中华草蛉幼虫、龟纹瓢虫、小花蝽和草间小黑蛛)对烟粉虱的捕食功能,明确了639020棉花在生长的关键时期对棉铃虫的控制效果及对棉田主要捕食性天敌捕食功能反应的影响。结果表明,639020棉花对二代和三代棉铃虫具有良好的控制作用,抗虫性分别比中棉所41提高了52.85%和16.22%,其中前者差异达显著水平,后者差异不显著。在棉花蕾期、花期和花铃期,639020棉田棉铃虫落卵量都比中棉所41棉田和中棉所49棉田低(除二代棉铃虫发生期);棉铃虫幼虫数量都极显著低于常规棉,且都低于防治指标,但与中棉所41棉田无显著差异。639020棉田中华草蛉、龟纹瓢虫、小花蝽和草间小黑蛛对烟粉虱的捕食功能与中棉所41棉田和常规棉田相比无显著变化。研究结果以期为新型转基因棉花环境安全性研究及其外源基因的抗虫遗传效应和生产应用前景进行安全性评价。     

利用花青素可视化跟踪表达系统快速筛选表达Cry1Ab/c基因的转基因玉米

以草甘膦抗性基因Epsps为标记基因, 在原核Kan^r基因两侧引入Cre(环化重组酶)基因识别的Lox-P位点, 同时以编码花青素合成转录因子的Bi和Cl基因为可视化选择报告基因, 构建了Bt杀虫蛋白基因Cry1Ab/c的可视化跟踪表达载体pBAC9017。用PDS1000/He基因枪转化玉米(Zea mays)自交系501的幼胚和胚性愈伤组织, 获得147个草甘膦抗性的玉米再生植株。其中106棵植株获得了结实种子, 16棵植株的结实种子有紫红色花青素基因的表达。经PCR检测表明, 外源Cry1Ab/c基因已经整合到玉米的基因组中。转基因植株种子蛋白粗提物用BT-Cry1Ab/1Ac金标免疫检测试纸条和ELISA检测, 结果表明, Cry1Ab/c在部分转基因植株后代中表达。     

饲喂Bt水稻的褐家鼠肠道中cry1Ab/Ac基因和蛋白的残留检测北大核心CSCD

分别用含有转cry1Ab/Ac基因水稻和亲本水稻的饲料饲喂野生褐家鼠,旨在检测外源cry1Ab/Ac基因和蛋白在褐家鼠雌鼠雄鼠空肠、回肠、盲肠中的残留情况。检测结果显示,饲喂转基因水稻50 d和110 d的雌雄褐家鼠肠道3个部位中没有检测到cry1Ab/Ac基因残留,在体外消化实验中过量外源基因全长及片段在4 h后开始逐步降解,约12 h全部降解。3个肠道部位提取的蛋白进行ELISA和Western blot分析,结果显示肠道内容物中无Cry1Ab/Ac蛋白残留。因此外源基因和蛋白不会在饲喂了转基因水稻的野生褐家鼠肠道中残留。     

饲喂Bt水稻的褐家鼠肠道中cry1Ab/Ac基因和蛋白的残留检测

分别用含有转cry1Ab/Ac基因水稻和亲本水稻的饲料饲喂野生褐家鼠,旨在检测外源cry1Ab/Ac基因和蛋白在褐家鼠雌鼠雄鼠空肠、回肠、盲肠中的残留情况。检测结果显示,饲喂转基因水稻50 d和110 d的雌雄褐家鼠肠道3个部位中没有检测到cry1Ab/Ac基因残留,在体外消化实验中过量外源基因全长及片段在4 h后开始逐步降解,约12 h全部降解。3个肠道部位提取的蛋白进行ELISA和Western blot分析,结果显示肠道内容物中无Cry1Ab/Ac蛋白残留。因此外源基因和蛋白不会在饲喂了转基因水稻的野生褐家鼠肠道中残留。     

转基因cry1Ab在高粱不同器官中的表达水平

用Cry1Ab/Cry1Ac板式试剂盒测定了Cry1Ab蛋白在转基因高粱不同器官中的表达水平。结果表明,不同组织器官的Cry1Ab蛋白含量有明显差异,其顺序为叶鞘>叶>颖壳>籽粒>根>茎髓,在花药中则检测不到;不同部位的叶片、叶鞘和茎髓的Cry1Ab蛋白含量也有较大差异,中部叶的Cry1Ab蛋白含量高于上部叶和基部叶,叶鞘中是中部>基部>上部,茎髓中则表现为基部最高。     

转基因水稻cry1Ab/Ac基因及蛋白在肉鸡肠道中的残留检测

旨在研究转基因水稻对饲喂肉鸡的影响,以含有转cry1Ab/Ac基因水稻的饲料饲喂肉鸡,分析了肉鸡空肠、回肠、盲肠、直肠中cry1Ab/Ac基因和蛋白残留情况,并用体外实验验证了外源基因的降解情况。结果表明,饲喂转cry1Ab/Ac基因水稻21 d和42 d的肉鸡肠道4个部位中没有检测到cry1Ab/Ac基因残留,体外消化外源基因的实验发现外源基因在肉鸡肠道中约4 h后开始逐步降解。对上述4个部位内容物进行ELISA和Western blot分析,均未检测到Cry1Ab/Ac蛋白残留。综合分析表明,转基因水稻中的外源基因和蛋白在肉鸡肠道中易被消化和降解。     

转Bt基因玉米根际土壤及秸秆残体中

采用ELISA法研究了田间种植条件下转Bt基因玉米MON810生育期根际土壤及还田秸秆中Cry1Ab蛋白的田间残留降解动态,并分别用移动对数模型、指数模型和双指数模型对秸秆分解释放Cry1Ab蛋白的田间降解动态进行拟合,估算了DT₅₀和DT₉₀值. 结果表明: Bt玉米不同生育期根际土壤中Cry1Ab蛋白含量差异较大,但总体随生育期的延长而显著降低. 收获后地表覆盖和埋入土壤两种秸秆还田方式下,秸秆中Cry1Ab蛋白在土壤中的降解规律基本一致,均呈现前期大量快速降解,中后期极少量稳定降解两个阶段. 秸秆还田7 d内,地表覆盖处理的Cry1Ab蛋白降解率均极显著高于埋入土壤处理;10 d时两处理的降解率基本一致,分别为88.8%和88.6%;20 d后,两处理秸秆中Cry1Ab蛋白的降解日趋缓慢;至180 d时仍能检测到少量的Cry1Ab蛋白. 3种模型均能较好地反映秸秆中Cry1Ab蛋白的田间降解规律,从相关系数(R)及DT₉₀值与实测值的吻合程度来看,双指数模型最优.     

Seasonal expression profiles of insecticidal protein and control efficacy against Helicoverpa armigera for Bt cotton in the Yangtze River valley of China

Seasonal levels of Bacillus thuringiensis (Bt) insecticidal protein and its control efficacy against Helicoverpa armigera (Hübner) in Bt transgenic cotton GK19 (carrying a Cry1Ac/Cry1Ab fused gene) and BG1560 (carrying a Cry1Ac gene) were investigated in Tianmen County, Hubei Province, located in the Yangtze River valley of China, in 2001 and 2002. The results showed that the toxin content in Bt cotton changed significantly over time, and that the structure, growth stage, and variety were significant sources of variability. Generally, insecticidal protein levels were high during the early stages of cotton growth; they declined in mid-season, and rebounded in late season. On most dates sampled, the toxin contents in leaf, square, petal, and stamens (including nonovule pistil tissue) were much higher than those in ovule and boll. Compared with BG1560, the expression of Cry1Ac/Cry1Ab protein in GK19 was more variable during the whole growth period of cotton. The field evaluation on larval population dynamics of H. armigera in Bt and conventional cotton showed that the larval densities in BG1560 and GK19 fields decreased, respectively, 92.04 and 81.85% in 2001, and 96.84 and 91.80% in 2002.     

A Sensitive Bioassay for the Detection of Cry1A Toxin Expression in Transgenic Cotton

In the process of development of insect resistant transgenic plants and also to evaluate the consistency in expression of the toxin under greenhouse and field conditions, immunological and bioassays are commonly used. The assay being described in this report, is based on the high levels of sensitivity of a cotton leaf feeding insect, the semilooper, Anomis flava (Fabricius) to Cry toxins (Cry1Aa, Cry1Ab and Cry1Ac). The assay is sensitive, quick and reproducible. Cry1Ac was the most toxic followed by Cry1Ab and Cry1Aa. LC 50 s of the three toxins on first instar larvae ranged from 0.79-6.08 ng cm -2 of leaf. LC 50 s of Cry1Ac for the fourth instar larvae ranged from 12.91-21.14 ng cm -2 while LC 50 s for Cry1Aa and Cry1Ab were in the range 53.0-138 ng cm -2 . The fiducial limits (at 95% probability) of the probit assay data indicated that there was no difference in response between the three different populations to each of the three toxins. The data from all assays were pooled for each of the three toxins separately and subjected to regression analysis to obtain a cumulative log dose response for first and fourth instar larvae. These can be used as standard curves to quantify toxin expression in plants based on mortality response of either first or fourth instar A. flava larvae. Apart from being used to detect expression in putative Bt cotton transgenic plants, the assay can also be used to follow the activity of Cry toxins in transgenic cotton plants in the field during the growing season.     

Bt-Cry5Aa 基因转化棉花及其抗虫性鉴定

我国棉花抗虫基因大都为Cry1Ab/c,抗性风险日趋增加。本研究依据棉花密码子偏好,人工合成Bt-Cry5Aa抗虫基因,通过花粉管通道法转入棉花,并通过卡那霉素法及PCR方法对不同世代转化株进行鉴定,同时进行了抗虫性测试。结果表明,通过花粉管通道法成功获得转Bt-Cry5Aa基因植株,通过田间卡那霉素鉴定,阳性株率T1为7.76%,T2为73.1%,T3为95.5%;PCR检测显示,T1阳性率为2.35%,T2为55.8%,T3为94.5%;田间抗性试验分析,转Bt-Cry5Aa株系对第2、3、4代棉铃虫校正死亡率分别达到85.42%、75.35%和62.79%,其抗虫性与GK19相比差异不显著;Bt-Cry5Aa能够部分替代目前主流鳞翅目抗虫基因,是棉铃虫的新抗源。     

Field efficacy and seasonal expression profiles for terminal leaves of single and double Bacillus thuringiensis toxin cotton genotypes.

Examination of commercial Cry1Ac transgenic Bacillus thuringiensis Berliner (Bt) cotton varieties (Bollgard, Monsanto, St. Louis, MO) and an experimental Cry1Ac + Cry2Ab transgenic Bt cotton variety (Bollgard II, Monsanto) for lepidopteran field efficacy was conducted during the 2000 growing season. In addition, a commercially available (Envirologix, Portland, ME) quantification assay (ELISA) was used to measure and profile the expression levels of Cry proteins in two of these varieties ['DP50B, Bollgard'; 'DP50BII, Bollgard II' (Delta & Pine Land, Scott, MS)]. Populations of beet army worms, Spodoptera exigua (Hübner), and soybean loopers, Pseudoplusia includens (Walker), were significantly lower (P < 0.05) in Bollgard II plots compared with Bollgard. Population numbers for fall army worms, Spodoptera frugiperda (J. E. Smith), and salt marsh caterpillars, Estigmene acrea (Drury), were lower in Bollgard II plots compared with Bollgard but means did not differ significantly (P > 0.05). Single and dual-toxin genotypes remained superior (P < 0.05) compared with conventional cotton against the tobacco budworm, Heliothis virescens (F.). The addition of Cry2Ab had no significant (P > 0.05) impact on Cry1Ac expression in Bollgard II compared with Cry1Ac expression in Bollgard. Furthermore, throughout the season Cry2Ab was present at much higher levels in the plant compared with Cry1Ac for Bollgard II plants. Possible species-specific reasons for increased efficacy of Bollgard II over Bollgard are discussed.     

Development of ELISA for the Determination of Transgenic Bt‐Cottons Using Antibodies against Cry1Ac Protein from Bacillus thuringiensis HD‐73

The area cultivated with Bt‐cottons expressing Cry1Ac gene increases year by year in China and other countries. To evaluate any potential adverse impacts on the environment from the release of Bt (Bacillus thuringiensis) technology, the development of a method for easily detecting the activity of the Cry1Ac toxins is of particular interest. The aim of this study was to develop sandwich‐ELISA for the detection of Cry1Ac protein in Bt‐cotton tissues. A specific antibody was obtained from rabbits inoculated with Cry1Ac protein derived from Bt strain HD‐73 and a secondary antibody conjugated to HRP could combine the Bt Cry1Ac protein specifically. The limit of detection was 5 ng/mL and there were no cross‐reactions between the positive control of Cry1Ab/1Ac, Cry1C, Cry2A, Cry3Bb1 and Cry9C. Extracts of proteins from cotton leaves were used to evaluate the suitability of the assay. Tris‐borate buffer and sodium carbonate buffer were employed for the extraction of protein, the limit absorbance of detection was 0.134 and 0.449, respectively, and the latter produced a higher background. The results showed that cultivars GK‐12, GK‐22, insect‐resistant cotton, bivalent transgenic cotton and shiyuan 321 assayed positively and NON was the negative sample. The PCR method was used for the validation of the developed assay. Although both methods allowed the same results to be obtained, ELISA needed simple equipment and took less time. The developed immunoassay method is considered reliable for the detection of Bt Cry1Ac protein.     

Field studies on the environmental fate of the Cry1Ab Bt-toxin produced by transgenic maize (MON810) and its effect on bacterial communities in the maize rhizosphere

Field studies were done to assess how much of the transgenic, insecticidal protein, Cry1Ab, encoded by a truncated cry1Ab gene from Bacillus thuringiensis (Bt), was released from Bt-maize MON810 into soil and whether bacterial communities inhabiting the rhizosphere of MON810 maize were different from those of the rhizosphere of nontransgenic maize cultivars. Bacterial community structure was investigated by SSCP (single-strand conformation polymorphism) of PCR-amplified 16S rRNA genes from community DNA. Using an improved extraction and detection protocol based on a commercially available ELISA, it was possible to detect Cry1Ab protein extracted from soils to a threshold concentration of 0.07 ng/g soil. From 100 ng of purified Cry1Ab protein added per gram of soil, only an average of 37% was extractable. At both field sites investigated, the amount of Cry1Ab protein in bulk soil of MON810 field plots was always lower than in the rhizosphere, the latter ranging from 0.1 to 10 ng/g soil. Immunoreactive Cry1Ab protein was also detected at 0.21 ng/g bulk soil 7 months after harvesting, i.e. in April of the following year. At this time, however, higher values were found in residues of leaves (21 ng/g) and of roots (183 ng/g), the latter corresponding to 12% of the Cry1Ab protein present in intact roots. A sampling 2 months later indicated further degradation of the protein. Despite the detection of Cry1Ab protein in the rhizosphere of MON810 maize, the bacterial community structure was less affected by the Cry1Ab protein than by other environmental factors, i.e. the age of the plants or field heterogeneities. The persistence of Cry1Ab protein emphasizes the importance of considering post-harvest effects on nontarget organisms.     

Control of resistant pink bollworm (Pectinophora gossypiella) by transgenic cotton that produces Bacillus thuringiensis toxin Cry2Ab

Crops genetically engineered to produce Bacillus thuringiensis toxins for insect control can reduce use of conventional insecticides, but insect resistance could limit the success of this technology. The first generation of transgenic cotton with B. thuringiensis produces a single toxin, Cry1Ac, that is highly effective against susceptible larvae of pink bollworm (Pectinophora gossypiella), a major cotton pest. To counter potential problems with resistance, second-generation transgenic cotton that produces B. thuringiensis toxin Cry2Ab alone or in combination with Cry1Ac has been developed. In greenhouse bioassays, a pink bollworm strain selected in the laboratory for resistance to Cry1Ac survived equally well on transgenic cotton with Cry1Ac and on cotton without Cry1Ac. In contrast, Cry1Ac-resistant pink bollworm had little or no survival on second-generation transgenic cotton with Cry2Ab alone or with Cry1Ac plus Cry2Ab. Artificial diet bioassays showed that resistance to Cry1Ac did not confer strong cross-resistance to Cry2Aa. Strains with >90% larval survival on diet with 10 microg of Cry1Ac per ml showed 0% survival on diet with 3.2 or 10 microg of Cry2Aa per ml. However, the average survival of larvae fed a diet with 1 microg of Cry2Aa per ml was higher for Cry1Ac-resistant strains (2 to 10%) than for susceptible strains (0%). If plants with Cry1Ac plus Cry2Ab are deployed while genes that confer resistance to each of these toxins are rare, and if the inheritance of resistance to both toxins is recessive, the efficacy of transgenic cotton might be greatly extended.     

多年种植Bt稻后外源蛋白在土壤中的积累

外源蛋白在环境中的残留与积累是转Bt基因作物环境安全评价的重要内容之一。我国已育成多个具有商业化前景的Bt稻品系,但目前多年种植Bt稻后Bt外源蛋白是否会在土壤中积累还不清楚。本研究在同一试验田连续9年种植了转cry1Ab/1Ac基因明恢63(华恢1号)和转cry2A基因明恢63水稻,采用酶联免疫吸附法(ELISA)跟踪监测了分蘖期和收获后60 d根际土中外源蛋白含量变化,试验第1年(2012年)和最后1年(2020年)还测定了苗期、开花期和成熟期根际土中外源蛋白含量。结果表明: 2012年,转cry1Ab/1Ac基因明恢63在苗期、分蘖期、开花期、成熟期和收获后60 d根际土中外源蛋白含量分别为1.25、1.77、1.97、1.71和0.30 ng·g^-1,2020年分别为1.30、1.69、2.03、1.77和0.43 ng·g^-1;2012年,转cry2A基因明恢63在苗期、分蘖期、开花期、成熟期和收获后60 d根际土中外源蛋白含量分别为0.91、1.52、1.53、1.37和0.12 ng·g^-1,2020年分别为0.95、1.43、1.61、1.40和0.15 ng·g^-1。多因素方差分析显示,时间效应对Bt外源蛋白积累不显著,而品种和生育期效应显著。Bt稻生长过程中根际土中可以检测出微量的Bt外源蛋白,但收获后60 d已经基本降解完毕,根际土中Bt外源蛋白含量不会随着种植时间的增加而累积。     

Monitoring and adaptive resistance management in Australia for Bt-cotton: current status and future challenges

In the mid-1990 s the Australian Cotton industry adopted an insect-resistant variety of cotton (Ingard) which expresses the Bt toxin Cry1Ac that is specific to a group of insects including the target Helicoverpa armigera. A conservative resistance management plan (RMP), that restricted the area planted to Ingard, was implemented to preserve the efficacy of Cry1Ac until two-gene transgenic cotton was available. In 2004/05 Bollgard II replaced Ingard as the transgenic cotton available in Australia. It improves on Ingard by incorporating an additional insecticidal protein (Cry2Ab). If an appropriate refuge is grown, there is no restriction on the area planted to Bollgard II. In 2004/05 and 2005/06 the Bollgard II acreage represented approximately 80 of the total area planted to cotton in Australia. The sensitivity of field-collected populations of H. armigera to Bt products was assayed before and subsequent to the widespread deployment of Ingard cotton. In 2002 screens against Cry2Ab were developed in preparation for replacement of Ingard with Bollgard II. There have been no reported field failures of Bollgard II due to resistance. However, while alleles that confer resistance to H. armigera in the field are rare for Cry1Ac, they are surprisingly common for Cry2Ab. We present an overview of the current approach adopted in Australia to monitor and adaptively manage resistance to Bt-cotton in field populations of H. armigera and discuss the implications of our findings to date. We also highlight future challenges for resistance management in Australia, many of which extend to other Bt-crop and pest systems.