Stylet penetration behaviors of the cotton aphid Aphis gossypii on transgenic Bt cotton

Stylet penetration behaviors of cotton aphids Aphis gossypii Glover on a transgenic cotton line "GK-12" expressing Bt toxic protein of Cry1A (Bt cotton) and a non-Bt conventional cotton line "Simian-3" (CK cotton) were recorded with the direct current electrical penetration graph (DC-EPG) technique. Cotton aphids reared on Bt cotton (abbreviated as Bt-aphids) and its parental non-Bt control line (CK-aphids) for more than 20 generations each, were used for recordings on two cotton lines. Among 47 selected parameters reflecting the activities of aphid stylets within plant tissues, there were eight parameters of CK-aphids showing significant differences between the performances of CK-aphids on Bt cotton and CK cotton, while for Bt-aphids, all the parameters were statistically equal between the performances on the two cotton lines. All parameters with significant differences indicated that CK-aphids could penetrate into Bt cotton more easily, but the phloem saps of Bt cotton were not as good as those of regular cotton for CK-aphids. Based on the present results, we concluded that there were some factors in Bt cotton affecting penetration behaviors of CK-aphids, but it just took several generations for CK-aphids to completely adapt Bt cotton, and Bt-aphids could feed on two cotton lines without difficulty.     

Impacts of transgenic Bt cotton on the stylet penetration behaviors of Bemisia tabaci biotype B: Evidence from laboratory experiments

Abstract Stylet penetration behaviors of Bemisia tabaci biotype B on two transgenic cotton lines “GK12” and “GK19” expressing Bt toxic protein Cry1A (Bt cotton) and a non-Bt conventional cotton line “Simian-3” (CK cotton) were recorded with the direct current electrical penetration graph (DC-EPG) technique. Our results suggested that EPG waveform patterns, types and characteristics [non-probe (NP), pathway (C), potential drops (pd) and phloem phase (E(pd))] of Bemisia tabaci biotype B were very similar on the three cotton lines. There were no obvious differences of pathway variables among whiteflies on the three cotton lines. Some phloem variables related to E(pd)₁ differed. Duration of 1st E(pd)₁ and mean duration of E(pd)₁ on both GK12 and GK19 were significantly shorter than that on CK cotton (P < 0.05). Fewer whiteflies on GK have long E(pd)₁. Other phloem variables including total duration of E(pd) summed, mean E(pd) duration and percentage of whiteflies reaching the phloem phase were similar among the three cotton lines.     

湖北棉区转Bt基因棉对棉铃虫的控制作用

2000-2001年通过田间系统调查,表明转Bt基因棉（品种为GK19）在湖北江汉平原棉区对棉铃虫抗性稳定。试验设3个处理：转Bt基因棉化防田（使用化学农药控制害虫）、转Bt基因棉自控田（依靠天敌控制害虫）及常规棉对照田（利用综合防治措施控制害虫）。从棉铃虫的第2代到第5代整个发生期内,即使在不进行化学防治的情况下,棉铃虫在Bt棉田的发生量也保持在极低的水平(最高百株虫量为12头)。室内饲养结果表明,转Bt基因棉对棉铃虫的生长发育（幼虫体重、蛹重）有较为明显的影响,使6龄幼虫体重减少25.6%,蛹重减少18.2%。棉铃虫幼虫取食转Bt基因棉组织后,发育迟缓,相对于常规棉喂养的整个发育历期延长17 d,使棉铃虫在田间的危害减少至少一个世代。另外,接虫试验表明,棉铃虫幼虫在常规棉上的取食时间是转Bt基因棉株上的6.1倍,极大地减轻了棉铃虫的危害程度。     

不同类型品种棉花上棉蚜适生性及种群动态

通过田间调查、室内网罩盆栽苗测定选择性等方法,考察了常规棉（泗棉3号,石远321）、杂交抗虫棉（辽棉19号,鲁棉研18号）、转单价基因抗虫棉（国抗12号,中棉所32）和转双价抗虫棉（SGK321,中棉所41）4种类型8个品种棉花上棉蚜的适生性及种群动态。结果表明： 棉蚜在各棉花品种上的种群动态有明显差异（P<0.05）,单株蚜量以转单价基因抗虫棉中棉32上最高,常规棉泗棉3号上最低,分别为297.81头/株和76.88头/株。棉蚜对4种类型棉花品种的选择性有明显差异（P<0.05）,其中对转单价基因抗虫棉有很强的选择性。根据棉蚜实验种群的参数判断,其在不同品种棉花上的生长发育、存活及繁殖存在显著差异： 若虫发育历期常规棉石远321上最长（6.46天）,双价棉中棉所41上最短（5.75天）; 存活率转单价基因抗虫棉中棉32上最高（88.21%）,双价棉SGK321上最低（76.46%）; 单雌产蚜量杂交抗虫棉辽棉19上最大（44.48头）,双价棉SGK321上最小（33.51头）; 内禀增长率转单价基因抗虫棉中棉32上最高（0.3695）,双价棉中棉所41上最低（0.3389）。综合评价,棉蚜的生存和繁殖适合性在转单价基因抗虫棉上最高,在双价棉上最低。     

Impact of transgenic cotton plants on a non-target pest, Aphis gossypii Glover

Abstract.  1. Transgenic crops have shown great promise for the control of target pest insects, but in some cases they can also influence non-target species. This study investigated the impact of Bt and Bt+CpTI transgenic cottons on the non-target cotton aphid, Aphis gossypii Glover, by comparing life-table parameters, feeding behaviour, and the fluctuating asymmetry of morphological traits of aphids reared on transgenic cotton and those on untransformed control plants.
2. Aphids on the Bt+CpTI cotton showed a shorter reproductive duration and maximum lifespan, lower survival rates and potential maximum fecundity, and an earlier occurrence of peak daily mortality in the first or second generation. However, the aphid population soon developed fitness and overcame the negative effect in the second or third generation. The aphids on the Bt cotton had significantly longer reproductive durations in the first generation, higher survival rates in the third generation, and apparently larger potential maximum fecundity in all three generations.
3. The percentages of accumulated duration of feeding waveforms E1 and E2 were significantly lower in aphids on the Bt+CpTI cotton than in those on the Bt or control cotton, whereas the frequencies of moving and finding feeding sites, and probe behaviour were significantly higher.
4. Fluctuating asymmetry in three morphological characters of aphids reared on transgenic and control cotton was detected. The fluctuating asymmetry value of the third segment of antenna in aphids on Bt+CpTI cotton was significantly higher than that of aphids on Bt or control cotton. Based on the fluctuating asymmetry value, the stress of cotton on the aphids could be ranked as Bt+CpTI cotton > Bt cotton > control cotton.     

Effects of proportion and configuration of Bacillus thuringiensis cotton on pest abundance, damage, and yield

Bacillus thuringiensis (Bt) transgenic cotton, Gossypium hirsutum L., kills several economically important pests, reducing injury and increasing yields. Refuges of non-Bt cotton are currently planted with Bt cotton in different designs to slow pest resistance evolution. To compare the effects of differences in Bt/non-Bt plant heterogeneity found in different refuge designs on square (flower bud) damage, abscissions, sap-feeding herbivore densities, and yield in cotton, four types of 24-row cotton plots were planted in 2001 and 2002: 1) seed mixtures of Bt and non-Bt varieties, 2) 12-row strips of Bt and non-Bt, 3) solid Bt, and 4) solid non-Bt. For both years cotton bollworm, Helicoverpa zea (Boddie), damage was less in solid Bt plots than strips and mixtures and all were less than solid non-Bt plots. Cotton fleahopper, Pseudatomoscelis seriatus (Reuter), damage was affected by refuge, but only in 2002 when damage was greater in solid Bt plots than all other plots and greater in strips than solid non-Bt plots. Abscissions were least in solid non-Bt plots, and less in mixtures and strips than solid Bt plots. In 2001, western flower thrips, Frankliniella occidentalis (Pergande), density was greatest in mixtures, whereas sweetpotato whitefly, Bemisia tabaci (Gennadius), was greatest in solid Bt plots, and greater in mixtures than solid non-Bt plots. Yield also was affected by refuge, it was greater for solid Bt plots than for solid non-Bt plots and mixtures in 2001, but the reverse was true in 2002.     

Tri-trophic interactions between Bt cotton, the herbivore Aphis gossypii Glover (Homoptera: Aphididae), and the predator Chrysopa pallens (Rambur) (Neuroptera: Chrysopidae)

Tri-trophic impacts of transgenic Bacillus thuringiensis (Bt) cotton GK12 and NuCOTN 99B were studied using a predator, the great lacewing Chrysopa pallens (Rambur), and its prey, the cotton aphid Aphis gossypii Glover, in laboratory feeding experiments. The parental nontransgenic cotton cultivar of GK12 was used as control. The predator was fed with uniform (aphids from a single cultivar) or mixed prey (aphids from the three cotton cultivars provided on alternate days). Mortality and development of the immature stages, pupal body mass, adult sex ratio, fecundity, and egg viability of C. pallens were measured. When fed GK12-originated aphid prey, pupal body mass of C. pallens was significantly higher than that of the control, more females emerged, and these females laid significantly more eggs. Other parameters were not impacted. Females emerging from larvae maintained on NuCOTN 99B-originated prey laid fewer eggs than those maintained on GK12. Other measurements did not differ significantly between the two Bt cotton cultivars. Compared with the control, mixed feeding significantly prolonged pupal development time and increased pupal body mass and percentage of females but did not affect other parameters. These results indicate that C. pallens is sensitive to aphid prey from different cotton cultivars. Transgenic Bt cotton GK12-originated aphid prey has no adverse impact on survival, development, and fecundity of C. pallens. Between the two Bt cotton cultivars, NuCOTN 99B-originated aphid prey provided to C. pallens in the larval stage may lower female fecundity. Mixed feeding of C. pallens with the two Bt cotton-originated prey and non-Bt prey may have some adverse impacts on pupal development.     

新疆棉区转Bt基因棉对棉铃虫生物学的影响

棉铃虫Helicoverpaarmigera高龄幼虫取食转Bt基因棉花组织后 ,化蛹率、羽化率、蛹重、体长均有显著下降 ,在转Bt基因棉花上棉铃虫的取食行为也受到较大的影响 ,表现为取食次数明显减少、吐丝下垂次数明显增加 ;无论是转Bt基因棉花还是常规棉花 ,棉铃虫 3龄幼虫主要分布于繁殖器官上 ,在转Bt基因棉花各繁殖器官上的分布概率为 :花 >棉铃 >棉蕾 ,常规棉花上分布概率为 :棉蕾 >棉铃 >花 ;棉铃虫高龄幼虫取食转Bt基因棉花各组织 ,成虫羽化后产卵量、卵孵化率均有明显下降 ;在较低的棉铃虫虫口密度下 ,转Bt基因棉花对棉铃虫有一定的产卵排趋性。     

Within-plant distribution of cotton aphids, Aphis gossypii Glover (Hemiptera: Aphididae), in Bt and non-Bt cotton fields

Knowledge of the vertical and horizontal distribution of Aphis gossypii Glover (Hemiptera: Aphididae) on genetically modified cotton plants over time could help optimize decision-making in integrated cotton aphid management programs. Therefore, the aim of the present study was to determine the vertical and horizontal distribution of A. gossypii in non-transgenic Bt cotton and transgenic Bt-cotton over time during two cotton seasons by examining plants throughout the seasons. There was no significant interaction between years and cotton cultivar treatments for apterous or alate aphids. Considering year-to-year data, analyses on season-long averages of apterous or alate aphids showed that aphid densities per plant did not differ among years. The number of apterous aphids found per plant for the Bt transgenic cultivar (2427 apterous aphids per plant) was lower than for its isoline (3335 apterous aphids per plant). The number of alate aphids found per plant on the Bt transgenic cultivar (12.28 alate aphids per plant) was lower than for the isoline (140.56 alate aphids per plant). With regard to the vertical distribution of apterous aphids or alate aphids, there were interactions between cotton cultivar, plant age and plant region. We conclude that in comparison to non-Bt cotton (DP 4049), Bt cotton (DP 404 BG (Bollgard)) has significant effects on the vertical, horizontal, spatial and temporal distribution patterns of A. gossypii, showing changes in its distribution behaviour inside the plant as the cotton crop develops. The results of our study are relevant for understanding the vertical and horizontal distribution of A. gossypii on Bt cotton cultivar (DP 404 BG (Bollgard)) and on its isoline (DP 4049), and could be useful in decision-making, implementing controls and determining the timing of population peaks of this insect.     

Neighbouring crop diversity mediates the effect of Bt cotton on insect community and leaf damage in fields

Effects of large-scale cultivation of transgenic crops on agricultural biodiversity remain unclear, particularly in the context of complex ecological interactions between transgenic crops and other organisms. Here we conducted a comprehensive survey to investigate the number of species, population abundance, community evenness and dominance of insects and weeds as well as leaf damage to weeds in Bt and non-Bt cotton fields at 27 sites across northern China. The role of neighbouring crop diversity around cotton fields in controlling insects and weeds in the cotton fields was also assessed. In addition, we conducted a 3-year field experiment to verify the results of the survey. Weed diversity in Bt and non-Bt cotton fields was similar, but the species number and diversity indices of insects are significantly decreased in Bt fields aligning with reduced leaf damage to broadleaf plant species including cotton as well as crops in neighbouring plots. The leaf damage to Bt and non-Bt cotton negatively associates with the diversity of neighbouring crops in cotton fields. Our study demonstrates the neighbouring crop diversity mediates the effects of Bt crops on agricultural diversity in complex interactions among transgenic crops, in-field weed and insect communities, and neighbouring crops.

     

Bt毒蛋白在转Bt基因棉中的表达及其在害虫-天敌间的转移

以常规棉泗棉3号作为对照,采用酶联免疫生测法（ELISA）和室内生物测定法,研究了转Bt基因棉新棉33B和GK-12不同组织器官中Cry1Ac或Cry1Ab毒蛋白的表达及其向靶标害虫（棉铃虫）、非靶标害虫（棉蚜）以及天敌（龟纹瓢虫）的传递和影响。研究结果表明,新棉33B各组织器官中Bt毒蛋白的表达量较高,为79.7～1 390.0 ng/g鲜重,GK-012较低为165～2640 ng/g鲜重。在花盛期,新棉33B各组织器官中Bt毒蛋白的表达量依次为：柱头、花 >子房、花瓣>群尖;而5～7叶期的初展嫩叶、现蕾初期的幼蕾及花铃期的幼铃表达量相当,而且与花盛期群尖的表达量没有明显区别。同样处于花盛期的GK-12,其各组织器官中Bt毒蛋白的表达量依次为：花药>柱头>花瓣>群尖>子房;而5～7叶期的初展嫩叶、现蕾初期的幼蕾及花铃期的幼铃表达量相当,而且与花盛期群尖的表达量没有明显差异。常规对照棉的幼铃、花药、柱头以及子房中痕量Bt毒蛋白的存在可能与传粉昆虫等的活动有关。在转Bt基因棉田采集的棉蚜和棉铃虫老龄幼虫,其体内均可检测到Bt毒蛋白;在新棉33B棉田采集的龟纹瓢虫幼虫和成虫体内也可检测出Bt毒素。当以Bt棉田的棉蚜饲喂龟纹瓢虫时,龟纹瓢虫的生长发育、存活以及繁殖等基本没有受到影响。     

转Bt基因棉花杀虫晶体蛋白的表达及光合特性的研究

转Bt基因棉花(GK、ZK)及非Bt基因棉花(CZ)杀虫晶体蛋白表达及光合特性的研究表明,杀虫晶体蛋白在转Bt基因棉花GK与ZK中的表达总量及在各器官中的分配均有所不同．转Bt基因棉花叶片的净光合速率的光响应与常规棉有所不同．转Bt基因棉花GK与ZK叶片的叶绿素含量、净光合速率、蒸腾速率的日变化有明显的不同,而胞间二氧化碳浓度、气孔限制值、叶温的日变化趋势则基本一致．胞间二氧化碳浓度的日平均值在两转Bt基因棉花间的差异达显著水平,而其它各指标在不同处理间的差异均未达显著．     

Effects of repeated cultivation of transgenic Bt cotton on functional bacterial populations in rhizosphere soil

The impact of multiple-year (0–5 years) cultivation of transgenic Bacillus thuringiensis (Bt) cotton on the functional bacterial populations in rhizosphere soil was investigated. The transgenic Bt + CpTI cotton line SGK321 and a non-Bt cotton line Shiyuan321 were planted in four fields in which Bt cotton had been continuously cultivated for 0, 1, 3, and 5 years. Rhizosphere soil samples were collected at the seedling, squaring, flower and boll, and boll-opening stages of cotton. Numbers of bacteria involved in nitrogen-fixing, organic phosphate-dissolving, inorganic phosphate-dissolving, and potassium-dissolving were measured with cultivation-dependent approaches. The data presented here showed no consistent statistically significant differences in the numbers of different groups of functional bacteria between rhizosphere soil of Bt and non-Bt cotton in the same field, and no obvious trends in the numbers of the various group of functional bacteria with the increasing duration of Bt cotton cultivation. These studies suggest that multiple-year cultivation of transgenic Bt cotton may not affect the functional bacterial populations in rhizosphere soil.     

Feeding behaviour of Helicoverpa armigera larvae on insect-resistant transgenic cotton and non-transgenic cotton

Abstract: Feeding behaviour of Helicoverpa armigera Hübner (Lep.; Noctuidae) larvae on non‐transgenic Bacillus thuringiensis (Bt) cotton (Gossypium hirsutum L.), Zhong 30, and transgenic cowpea trypsin inhibitor (CpTI)‐Bt cotton, SGK 321, and non‐transgenic cotton, Shiyuan 321, was investigated in both choice tests and no‐choice tests. The results of choice tests suggested that neonates have the ability to detect and avoid transgenic cotton. In the choice tests of neonates with both transgenic and non‐transgenic cotton leaves, a significantly greater proportion of larvae and higher consumption were observed on non‐transgenic cotton than on the transgenic Bt or CpTI‐Bt cotton. In the choice tests with leaves of two transgenic cotton lines, the proportion of neonates on leaf discs of the two lines was not significantly different, but there was significantly higher consumption on CpTI‐Bt transgenic cotton than that on Bt transgenic cotton. In addition, significantly more neonates were found away from the leaf discs, lower consumption and higher mortality were achieved in the choice test with two transgenic cotton leaves than in the choice tests containing non‐transgenic cotton leaves. Leaves and buds were examined in choice tests of fourth instars. It appeared that fourth instars were found in equal numbers on transgenic and non‐transgenic cotton, except when larvae were exposed to leaves for 3 h. However, the total consumption on transgenic cotton was lower than that of the non‐transgenic cotton, so fourth instars may still have the capacity to detect transgenic cotton and reduce feeding on it, although they showed no preference on either transgenic or non‐transgenic cotton. More larvae were found off diet in the treatments with leaves than that of buds, and the number of injured leaf discs by per fourth instar was significantly higher than that of buds in choice tests, suggesting that leaf is a less preferred organ for H. armigera larvae, elicited more larval movements. Similarly, in no‐choice tests of fifth instars, significantly fewer feeding time and more moving time occurred on leaf than that of bud, boll and petal. When cotton line was considered, compared with non‐transgenic cotton, significantly lower feeding time and higher resting time occurred on the two transgenic cottons. Overall, H. armigera larvae have the ability to detect the transgenic Bt and CpTI‐Bt cottons or the less preferred organs and selectively feed more on the non‐transgenic cotton or the preferred organs, especially the neonates, which have a high capacity for avoiding transgenic cotton.     

转Bt基因抗虫棉对棉蚜的杀虫剂敏感性及解毒酶系的影响

采用浸叶法,以亲本常规棉作对照,室内测定了吡虫啉和辛硫磷对在转Bt基因棉上取食不同世代棉蚜Aphis gossypii Glover的毒力,并用酶标仪测定了转Bt基因棉对棉蚜酯酶、羧酸酯酶和乙酰胆碱酯酶活力的影响。结果表明,棉蚜对吡虫啉和辛硫磷的敏感性并未受Bt棉的影响,2种杀虫剂对分别取食Bt棉1代和多代（60代以上）的棉蚜与取食亲本常规棉棉蚜的LC₅₀值之间均无显著差异。在抗虫棉GK12上取食1代和21代的棉蚜,其酯酶、羧酸酯酶和乙酰胆碱酯酶的活力与取食亲本常规棉的棉蚜之间差异不显著。可见,转Bt基因棉对棉蚜的杀虫剂敏感性和解毒酶活力无显著影响。     

种植转Bt基因抗虫棉对土壤生物学活性的影响

采用温室盆栽实验,研究了种植转Bt基因棉（苏抗103）和同源常规棉（苏棉12）对根际土壤生物学活性的影响。结果表明：与对照常规棉相比,种植转Bt基因棉对根际土壤脱氢酶、碱性磷酸酶、蔗糖酶和土壤呼吸的影响因生育期而异,土壤脲酶、蛋白酶和微生物量C在各生育期均没有显著差异;土壤蔗糖酶、土壤脱氢酶和土壤呼吸分别只在苗期（苏抗103〉苏棉12,增幅为25．5％）、花铃期（苏抗103〉苏棉12,增幅为21．6％）、花铃期（苏抗103〉苏棉12,增幅为36．1％）存在显著差异;土壤磷酸酶在花铃期和吐絮期活性显著下降（降幅分别为22．1％和32．9％）。     

Feeding, oviposition and survival of Liriomyza trifolii (Diptera: Agromyzidae) on Bt and non-Bt cottons

The effects of Bt transgenic cottons (Bt-I expressing cry1Ac and Bt-II expressing cry1Ab and cry2Ab or cry1Ab and cry1Fa) and non-Bt cottons on feeding, oviposition and longevity of adults, and development and survival of Liriomyza trifolii larvae were studied under laboratory conditions; and infestation on four Bt and two non-Bt cotton traits were investigated under field conditions. Laboratory choice and no-choice tests showed that L. trifolii adults were capable of distinguishing between Bt cottons and non-Bt cottons. In a choice test on younger plants (4-5 leaves), the adults were found more often and made more feeding punctures (FP) on non-Bt cottons than on Bt cottons. On older plants (8-9 leaves), adults made the most FP on non-Bt cotton followed by those on Bt-II cottons and the least on Bt-I cotton. The females oviposited more eggs (6.7 eggs per leaf) on non-Bt cotton than on Bt-I (1.7 eggs per leaf) and Bt-II (0.8 eggs per leaf) cottons on younger plants and oviposited similar numbers of eggs (0.7-1.3 eggs per leaf) on non-Bt and Bt cottons on older plants. In a no-choice test, the females also fed more FP on non-Bt cottons than on Bt cottons on both younger and older plants. The females oviposited more eggs (15.6 eggs per leaf) on non-Bt cotton than on Bt-I (8.2 eggs per leaf) and Bt-II (6.5 eggs per leaf) cottons on younger plants and similar numbers of eggs (2.5-3.3 eggs per leaf) on non-Bt and Bt cottons on older plants. Larval and puparial survivals were not different among Bt and non-Bt cottons. The occurrence and damage of leafminers on cottons in the field showed that L. trifolii infested more plants and leaves and had more mines on non-Bt cotton than on Bt cottons.     

转Bt基因棉花国抗62对棉铃虫生长发育的影响及田间抗虫效果

为了明确新疆第一个自主转Bt基因棉花品种国抗62对棉铃虫Helicoverpa armigera生长发育影响及田间抗虫效果,2005年进行了室内生物测定和田间小区试验。在室内以国抗62（转Cry1Ac基因棉花）和中棉35（对照常规棉花）的叶片饲喂棉铃虫幼虫,从幼虫发育历期、体重、存活率、化蛹等方面,分析了棉铃虫生长发育动态。结果表明,国抗62对棉铃虫生长发育的抑制作用非常显著。与对照相比,取食国抗62的棉铃虫幼虫1～6龄龄期分别延长了1.0,7.8,8.2,17.8,20.3和＞21.3天;幼虫发育到6龄时存活率仅为2.6%,最终无一化蛹,而对照幼虫发育到6龄时存活率为91.8%,最终化蛹率为89.8%。田间小区调查结果显示国抗62对第2代棉铃虫有非常好的抗虫效果：两个品种棉田棉铃虫落卵量无显著差异,但国抗62棉田比对照棉田虫口数量降低85.7%,顶尖被害率降低94.4%,蕾铃被害率降低95.1%,差异达到显著和极显著水平。但国抗62对第3代棉铃虫的田间抗虫效果欠佳。棉铃虫在新疆棉田以第2代为害为主,因此,国抗62能够起到有效的控制作用。     

转CpTI-Bt基因棉和转Bt基因棉对棉铃虫幼虫存活、生长及营养利用的影响

2000年7月中旬和8月中旬, 分别测定了采自田间的转CpTI-Bt基因双价抗虫棉（SGK321, 以下简称CpTI-Bt棉）和转Bt基因抗虫棉（中30,以下简称Bt棉）对棉铃虫Helicoverpa armigera幼虫存活、生长的影响。结果表明：7月中旬两种转基因抗虫棉抗虫效果均较好,尤其是CpTI-Bt棉棉叶和花瓣对4龄幼虫3天内致死率为92%以上;8月中旬两种转基因棉的抗虫活性均明显降低,且Bt棉的杀虫活性显著低于CpTI-Bt棉,其幼虫死亡率与对照受体棉中16的死亡率之间无显著差异,仅显著抑制了幼虫的生长;石远321(SGK321受体品系)的花瓣具有一定的抗虫活性,可显著降低取食幼虫的体重,甚至造成部分幼虫死亡; CpTI-Bt棉中,花瓣和棉叶的抗虫性明显高于蕾和铃心。对5龄幼虫取食棉铃1日后的营养指标测定结果显示： 两种转基因抗虫棉处理的幼虫相对生长率和相对取食量均显著低于石远321,但两者之间无显著差异; CpTI-Bt棉处理的幼虫近似消化率显著低于石远321和Bt棉,但其食物利用率显著高于石远321和Bt棉。     

Effects of transgenic Bt cotton on overwintering characteristics and survival of Helicoverpa armigera

The effects of transgenic Bt cotton on the overwintering generation of the cotton bollworm, Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae), are unknown. We hypothesized that a Bt cotton diet may adversely affect fitness of this generation and examined fresh weight, lipids, glycogens, low-molecular-weight sugars and SCPs (supercooling points) of pupae, as well as survival of larvae, diapausing pupae and adult emergence in comparison with controls. Field and laboratory experiments showed that larvae fed on Bt cotton had a decreased pupation rate, and fewer entered diapause and emerged as adults compared with larvae fed non-Bt cotton. Furthermore, larvae fed Bt cotton had reduced pupal weight, glycogen content and trehalose levels both in diapausing and in non-diapausing pupae, and only diapausing pupae had an increased SCP compared to controls. The SCPs of diapausing pupae reared on Bt cotton were significantly higher than those reared on non-Bt cotton. The trehalose levels of diapausing pupae reared on Bt cotton were significantly lower than those of larvae reared on non-Bt cotton. Thus, these results suggest that a Bt cotton diet weakens the preparedness of cotton bollworm for overwintering and reduces survival of the overwintering generation, which will in turn reduce the density of the first generation in the following year. Effects of transgenic Bt cotton on the overwintering generation of cotton bollworm appear to have significantly contributed to the suppression of cotton bollworm observed throughout northern China in the past decade.