Bt Hybrids Research Articles

Natural Enemies in Different Bt Cotton Hybrids under Protected and Unprotected Conditions

A field experiment was conducted to analyse the population dynamics of natural enemies including Chrysoperla, coccinellids, and spiders, in Bt cotton under both protected and unprotected conditions. The results indicated that the population of natural enemies was significantly higher under unprotected conditions compared to protected fields, where insecticides were applied. Among the tested hybrids, G. Cot. Hy.10 BG Ⅱ recorded the highest predator activity, showing a greater population of Chrysoperla, coccinellids, and spiders in unprotected conditions. In contrast, the lowest predator activity was observed in RCH 2 BG Ⅱ, while Ajeet 155 BG Ⅱ and ATM BG Ⅱ had minimal natural enemy presence. These findings highlight the importance of unprotected conditions in preserving natural enemies and suggest that certain Bt hybrids, such as G. Cot. Hy.10 BG Ⅱ, may better support predator populations. This research is crucial for understanding how insecticide use affects natural enemy populations and identifying hybrids that promote predator activity. Incorporating natural enemies into pest management strategies can enhance the sustainability of cotton production. Predators of pests, coccinellids and Chrysoperla, were observed from the 33rd to 52nd, whereas spider populations were observed from the 31st to 52nd SW under unprotected conditions.

Low temperature exposure influences nitrogen metabolism resulting in decreased Cry1Ac insecticidal endotoxin content in cotton seeds

BackgroundSudden temperature drops, resulting from extreme weather events, often occur during the boll-setting period of cotton in Xinjiang, China, causing decreased expression of Bacillus thuringiensis (Bt) insecticidal proteins in cotton bolls. The precise threshold temperatures and durations that lead to significant changes in Cry1Ac endotoxin levels under low temperatures remain unclear. To address this, we investigated the effects of different temperatures and stress durations on Cry1Ac endotoxin levels in cotton bolls. In 2020–2021, two Bt transgenic cotton varieties, conventional Sikang1 and hybrid Sikang3, were selected as experimental materials. Various low temperatures (ranging from 16 to 20 °C) with different durations (12 h, 24 h and 48 h) were applied during the peak boll-setting period.ResultsAs the temperature decreased, the Cry1Ac endotoxin content in the boll shell, fiber, and seed exhibited a declining trend. Moreover, the threshold temperature which caused a significant reduction in Cry1Ac endotoxin content increased with the prolonged duration of low-temperature stress. Among the components of cotton bolls, seeds were most affected by low-temperature stress, with the threshold temperature for a significant reduction in Cry1Ac endotoxin content ranging from 17 °C to 19 °C. Correlation analysis indicated that low temperatures led to a decrease in protein synthesis capacity and an increase in degradation ability, resulting in reduced Cry1Ac endotoxin content. Pathway analysis revealed that both free amino acid and peptidase had significant negative effects on Cry1Ac endotoxin content.ConclusionIn summary, when the daily average temperature was ≤ 19 °C, implementing cultural practices to reduce free amino acid content and peptidase activity could serve as effective cold defense strategies for Bt cotton production.

Longitudinal trials illustrate interactive effects between declining Bt efficacy against Helicoverpa zea (Lepidoptera: Noctuidae) and planting dates of corn.

Helicoverpa zea (Boddie) (Lepidoptera: Noctuidae) has evolved resistance to insecticidal toxins from Bacillus thuringiensis (Bt) Berliner (Bacillales: Bacillaceae) expressed in genetically engineered corn, Zea mays L. This study provides an overview of field trials from Georgia, North Carolina, and South Carolina evaluating Bt and non-Bt corn hybrids from 2009 to 2022 to show changes in susceptibility in H. zea to Bt corn. The reduction in kernel injury relative to a non-Bt hybrid averaged across planting dates generally declined over time for Cry1A.105 + Cry2Ab2 corn. In addition, there was a significant interaction with planting date used as a covariate. The reduction in kernel injury remained above 80% and did not vary with planting date from 2009 to 2014, whereas a significant decline with planting date was found in this reduction from 2015 to 2022. For Cry1Ab + Cry1F corn, the reduction in kernel injury relative to a non-Bt hybrid averaged across planting dates did not vary among years. The reduction in kernel injury significantly declined with planting date from 2012 to 2022. Kernel injury as a proxy for H. zea pressure was greater in late-planted trials in non-Bt corn hybrids. Our study showed that Bt hybrids expressing Cry1A.105 + Cry2Ab2 are now less effective in later planted trials in reducing H. zea injury; however, this was not the case during the earlier years of adoption of corn expressing these 2 toxins when resistance alleles were likely less frequent in H. zea populations. The implications for management of H. zea and for insect resistance management are discussed.

Yield analysis and corn earworm feeding in Bt and non-Bt corn hybrids across diverse locations.

Corn, Zea mays L. (Poales: Poaceae), growers in the US Cotton Belt are required to plant 20% of total corn acres to non-Bt hybrids for resistance management (non-Bt refuge). Most growers do not meet this requirement, in part, because they perceive non-Bt hybrids to yield less than Bt hybrids. We planted multiple non-Bt and Bt hybrids from a single company in small-plot replicated trials at a single location from 2019 to 2023, as well as in small-plot replicated trials at multiple locations during 2022 and 2023. In the single location, we measured kernel injury from corn earworm, Helicoverpa zea Boddie (Lepidoptera: Noctuidae), and we recorded yield at all locations. In the single location trial, yields only separated among hybrids in 3 out of 5 years. In the multiple location trial, yields were variable between both years. We found that Bt hybrids tended to yield higher than non-Bt hybrids overall, but this was influenced by the inclusion of non-Bt hybrids that had a lower overall genetic yield potential in the environments we tested them in. In both tests, when hybrids were analyzed during each year, both Bt and non-Bt hybrids were among the statistically highest yielders. Our study demonstrates the importance of comparing multiple Bt and non-Bt hybrids to draw yield comparisons. This highlights the need for corn seed company breeders to put effort into improving yield for non-Bt hybrids. Hopefully this effort will translate into increased planting of non-Bt refuge corn for growers in the US Cotton Belt.

Comparative study of high-density planting straight cotton varieties with normal sown Bt hybrids

Comparative study of high-density planting straight cotton varieties with normal sown Bt hybrids

Incidence of Cotton Thrips (Thrips tabaci Lindeman) and Its Correlation with Weather Parameters

Investigations on incidence of cotton thrips (Thrips tabaci Lindeman) on Bt and non-Bt cotton hybrid were carried out at Main Cotton Research Station, Navsari Agricultural University, Surat (Gujarat) during Kharif, 2017-18. The thrips incidence initiated from fourth week of June and it continued till first week of December in Bt and non-Bt cotton. The peak activity of thrips was observed during third week of August in Bt hybrid and the higher fluctuation of thrips was observed during the second week of August to third week of September and first week of October. Thrips population had significant negative correlation with maximum temperature in Bt cotton. In case of non-Bt, the peak activity of thrips was found during first week of September. As far as association with abiotic factors was concerned, maximum temperature and bright sunshine hours had significantly negatively correlation, while minimum temperature and morning relative humidity were positively associated.

Comparative efficacy of different cotton hybrids containing Bt genes against Pectinophora gossypiella (Saunders)

Field experiment was conducted at Agricultural Research Station, Dharwad farm, during 2018 and 2019 toevaluate performance of eighteen different cotton genotypes representing four different Bt events. Damage due to pink bollworm (PBW) was least in intraspecific (H×H) hybrids compared to interspecific hybrids (H×B) hybrids. Cotton hybridEverest recorded least flower damage of 9.40 per cent, followed by Jadoo (9.71%) and were on par. The highest per centflower damage of 22.57 was registered in (H × H) non Bt hybrid DCH-32. Least boll damage of 13.93 per cent was recordedin Everest BG-II and was on par with Jadoo (14.94%) and highest per cent boll damage of 41.26 was recorded in DCH-32The seed cotton yield was highest in Everest BG-II (15.20 q/ha). Among BG-I genotypes, VCH-5 (Event-1) recordedhighest yield (9.84 q/ha) and the least yield was recorded in DCH-32(5.97 q/ha).

Enhancing non-Bt corn refuge based on corn grower and seed dealer surveys

Abstract To delay Bacillus thuringiensis (Bt) resistance, southern US corn growers are required to plant 20% of their total corn acres to non-Bt hybrids. However, most do not, possibly due to negative perceptions or the lack of availability of non-Bt hybrids. We surveyed 174 corn growers and 32 corn seed dealers in eastern North Carolina, an area that historically has planted little non-Bt corn. Our questions focused on planting behavior and hybrid choice, barriers to planting non-Bt corn, and preferences and challenges for non-Bt corn sales. Only 32% of growers surveyed planted the mandated non-Bt refuge acres. Growers from counties with smaller crop operations and in counties where growers had less graduate education planted less non-Bt seed. Grower perceptions of yield differences between Bt and non-Bt hybrids were ambiguous, but only a few had limited availability or knowledge of non-Bt seed options. Seed dealers were familiar with non-Bt corn hybrids in their portfolio, but not as familiar with non-Bt refuge requirements. Furthermore, dealers indicated obstacles in providing diverse herbicide packages and seed treatments for non-Bt hybrids. We highlight the need for enhanced communication and education initiatives. Strengthening educational outreach to clarify refuge requirements and addressing perceived yield disparities between Bt and non-Bt hybrids could also increase planting of non-Bt refuge. Finally, incentivizing seed dealers to offer and promote non-Bt seed options, coupled with diverse herbicide packages, might increase refuge planting. Our surveys underscore the complexity surrounding grower behaviors, seed dealer dynamics, and the importance of educational efforts and incentives to non-Bt refuge.

Validation Cropping Systems and Input Management in Calcareous Vertisols

Inputs were tested and validated to supply optimum P and Zn content in index leaf of Bt hybrid cotton during squaring to flowering stage, such as seed treatment with NPK consortia to encourage soil biological activities in low organic carbon highly Calcareous Vertisols alongwith 75% RDF. Bentonite sulphur @20 kg ha-1 yr-1 soil application (SA) + RDF; Sagarika seed treatment @ 0.2% alongwith twice foliar sprays @ 0.002% at squaring and flowering + RDF; Nano ZnO 4% Seed treatment twice foliar sprays@0.004% + RDF produced significant agronomic response during 2019, exception was during 2020, the magnitude was 50% less due twice torrential (>60-100mm) and five times medium (25-50mm) rains during July and August months upset the reproductive physiology of cotton, shedded all the fruiting bodies, unable to maintain index leaf NPK, besides heavy pink bollworm attack. All these treatments were applied with 100% RDF @90:45:45 N:P2O5:K2O granular, two splits of basal spot application having 6.5% Sulphur containing, N: P2O5: K2O @ 22.5 kg ha-1 twice on 15, 30 DAS and twice as Urea at 45 and 60 DAS, Bentonite Sulphur @ 20 kg ha-1 +RDF or seed treatment and foliar applications of bio-stimulants Sagarika @ 0.02% and twice foliar applications of the same @ 0.002% and Nano ZnO @ 0.004% twice produced 67-86 ppm Zn in index leaf of the Bt hybrid cotton, similar to that of chelated Zn 0.5%. These inputs produced 161-287 kg lint ha-1 i. e. more than double 38 to 50% due to better nutrient uptake, biomass production, boll number with more than ₹. 15 to 30, 000/- ha-1 profitability and 1.5 to 2.2 C:B ratio, FUE 1.6 to 1.2 and lowest cost of production in both the years. Large scale OFTs in Kalmeshwar Tq, Nagpur district (M.S.) India in highly Calcareous soils, on suitable field and horticulture crops, irrigations and inputs management confirmed the beneficial effect of RDF 150% @120:60:60 N:P2O5:K2O three splits fertilizers mixture of SSP + Urea + 20:20:0:13 soil application and also Bentonite sulphur or with and without two winter irrigations in late September besides seed treatment with PGPRs or Sagarika 0.002% before sowing and twice foliar applications with the same or alongwith chelated micronutrients 0.5% + WSF 17:44:0 and 0:0:50 2.0% + Boron 0.3% alternately with ZnSO4 0.5% or nano ZnO 0.004% alongwith Urea 2% and Boron 0.3% or were help full in doubling the seed cotton yields besides reducing the pre mature leaf reddening by maintaining optimum index leaf nutrient content.

Variability in bacterial endophytes in leaves of transgenic Bt and non-Bt cotton crop varieties and their role in suppression of bacterial leaf blight pathogen X. a. pv. malvacearum and the incited disease reaction

Microbial epiphytes and endophytes are an integral part of the plant system and are known to play various roles in crop growth and crop health management. The transgenic crop plays an important role in crop pest management, however, environmentalists and ecologists have reservations about the cultivation of these crops. Whether the transgenic Bt cotton and non-Bt cotton vary in their microbial habitat ecology is not yet studied. In the present investigations, the leaf endophytic bacteria were detected in the leaves of both transgenic Bt and non-Bt cotton hybrids. However, there were differences in the endophytic bacterial types and their population densities i.e. bacterial colony-forming units (cfu) in the leaves of Bt and non-Bt cotton varieties. At least ten different leaf endophytic bacteria were detected from two cotton varieties i.e. RCH-2 and Bunny (of transgenic Bt and non-Bt versions). A maximum of four types of leaf endophytic bacteria was present in RCH-2 Bt cotton leaves. The population density of leaf endophytic bacteria ranged from 50 cfu/leaf to 5 x 103 cfu/leaf and varied with individual leaf endophyte and cotton variety. These bacterial leaf endophytes were observed to inhibit or suppress the growth of bacterial leaf blight pathogen Xanthomonas axonopodis pv. malvacearum (Xam) under in-vitro test. Leaf endophyte no.7 was more effective followed by leaf endophyte no.4 in suppressing the Xam population and population of other endophytes in the interaction studies. Interaction of leaf endophytes and Xam in cotton leaves suggested that endophytes of transgenic Bunny-Bt were effective on Xam in transgenic Bunny–Bt hybrid only and so these changed the induction of susceptible water-soaking disease reaction into hypersensitive browning resistance reaction (HR). However, these endophytes of Bt-cotton were not effective in the non-Bt version in changing the susceptible reaction of Xam into an HR reaction. This indicated that the endophytes of the respective Bt and non-Bt crops were able to change the susceptible reaction of Xam into a hypersensitive one in their respective host, indicating that the use of leaf endophytes can be effective in their own habitat crop as a biocontrol agent against Xam. The specificity of leaf endophytes has to be considered in biological disease management programs.

Validation of Bio-stimulant Seed Treatment, Soil and Foliar Application of Nano DAP, Urea, K, Zn, Cu, B Formulations in a Flood Affected Bt Hybrid Cotton

Bt hybrid cotton faced 30-60% excess rains in 70% years since its release and four times water logging in 2021, in a deep and shallow Vertisols with Calcareous sub-strata forced to confirm all the agronomical advices to it. Water logging reduced the biomass, boll number and cotton lint yields to more than 50 percent except the fibre quality. Prevailing runoff and leaching losses of soil applied fertilizer nutrients were accumulated at downstream, which increased the soil test values. Water logging caused reduction of index leaf N, P, K, Zn and B nutrient status below the threshold levels. Soil application of Zn and B once in three years alone or seed treatment formulation with N, P, K Bio-inoculant consortia along with nano ZnO 0.0004% + CuO 0.0001% as seed treatment at the time of sowing with or without foliar application of NPK WSF 2%, Zn 0.5%, B 0.3% or 0.04% nano formulations of DAP alternated with Urea alongwith ZnO and K with common insecticides and fungicidal sprays significantly improved index leaf nutrient status, biomass, boll number and seed cotton yields in both the soils. Validation of these results in station trials during 2022-24 found the need for atleast two foliar application of nano nutrients each DAP + ZnO + K followed by nano Urea+ ZnO + K 0.004% alternately at the mid and end September and October months. This increased N, P, K, Zn, B content in index leaves and seeds with additional cotton lint yield 209 kg ha-1 worth 174 US $ ha-1 net profit by soil application ZnSO4 20 and Borox 5 kg ha-1 yr -3 in Vertisols and three times foliar application at squaring, flowering and boll formation stage with nano ZnO 0.004%+ B 0.3% or ZnSO4 0.36% +Boron 0.2% in Vertisols with calcareous sub-strata.

Soil Application of Sea Weed Extract Granules and Foliar Application of Nano ZnO to Bt Hybrid Cotton to Vertic inceptisols

Bt hybrid cotton was significantly benefitted by the soil application of Sagarika sea weed extract granules at 25 kg ha-1 yr-1 along with the recommended basal fertilizers dose or foliar application of nano ZnO 4% at 0.04% at squaring and flowering stages. These treatments significantly enriched index leaf residual P and Zn content beyond 20 μg g-1 fresh weight during boll development stage and this resulted in significant improvement in lint yield by 7.5% i.e. 35 kg lint ha-1 yr-1, C:B ratio by 5.0% and net returns to the tune of ₹. 5000 ha-1 over alone 100% RDF in eroded Vertic inceptisols deficient in N, Mg, S, Zn and B. Excess rains at seedling and vegetative stage followed by drought at reproductive stages in both years, reduced the economic viability of seed treatment with bio-stimulants and foliar applications besides soil and foliar application of Zn, S, B alone or together to Bt hybrid cotton.

Incidence pattern of pink bollworm, Pectinophora gossypiella (Saund.)on different event Bt and non-Bt cottons

A field experiment was conducted at the Agricultural Research Station, Dharwad Farm, Dharwad, Karnatakaduring 2018-19 to evaluate the performance of cultivated cotton genotypes including Bt and non-Bt against pink bollworm,Pectinophora gossypiella (Saund.) under rainfed conditions. Based on seasonal mean green boll damage, Everest (13.56%)performed better against pink bollworm over single gene BG-I Bt variety PAU Bt-1 (16.55%), BG-I Bt hybrid MRC 6918(25.88%) (Both expressing Cry1Ac) and Arjun-21 Cry1A) and BG-II hybrid MRC 7918 (15.52%).DCH-32 (Non Btinterspecific hybrid) had maximum infestation of 37.59 per cent followed by H×H hybrid DHH-263 (36.34%), Suvin(21.38%), DDhc-11 (21.59%), Sahana (20.21%) and DLSa-17 (18.65%). The maximum larval recovery was 12.66 per 20green bolls in DCH-32 followed by DHH-263 (12.58) and Suvin (11.12). In general, Non-Bt genotypes had higher incidencethan Bt genotypes. Similarly, among Bt toxin, Cry1Ac and Cry2Ab expressing genotype had lower incidence.

Comparison of cotton (Gossypium hirsutum) hybrids and their non-transgenic in India

It is still not clear whether differential response of Bt cotton and conventional non-Bt cotton genotypes in terms of growth, phenology and yield ability are hypothetical or realistic. This study investigated the response of three Bt cotton hybrids in comparison to their conventional non-transgenic version (near-isogenic lines) along with two locally adapted genotypes for growth, yield attributes, phenological characteristics and rooting behavior. Therefore, two experiments were conducted during summer season of year 2016 and 2017 to evaluate differences among 3 popular Bt cotton hybrids along with their non-Bt version. First field experiment was conducted as a pot study wherein shoot and root parameters of 3 Bt cotton hybrids (Ankur 3028, MRC 7017, Bioseed 6588) were compared with their non-Bt version along with 2 local checks (i.e.,hirsutum cotton Cv. F2228 and arboreum cottonCv. FDK124). Second field experiment evaluated growth, phenological characteristics, yield attributes and productivity potential of above mentioned Bt and non-Bt hybrids. Findings of pot experiment could not establish any significant difference among studied Bt and non-Bt hybrids for root and shoot characteristics. However, arboreum cotton FDK124 exhibited higher root length than all genotypes. Results of second experiment revealed significant differences for phenological characteristics, wherein Bt version of all the tested hybrids exhibited earliness for flowering initiation, 50 % flowering and days to maturity over their non-Bt version. Seed cotton yield (SCY) in all hybrids possessing Bt gene was significantly higher than their non-Bt version primarily due to higher bolls plant-1. Studies conclude that introgression of Bt gene could not alter rooting parameters of evaluated cotton genotypes but significantly affected phenological stages by inducing earliness and higher SCY in Bt versions due to improved bolls plant-1. Keywords: Bt cotton; Near-isogenic lines; Phenology; Root dry matter; Seed cotton yield

Discovery of benzoxazole-thiazolidinone hybrids as promising antibacterial agents against Staphylococcus aureus and Enterococcus species.

Antibiotic resistance is rapidly exacerbating the unceasing rise in nosocomial infections caused by drug-resistant bacterial pathogens such as methicillin-resistant Staphylococcus aureus (MRSA), carbapenem-resistant Enterobacteriaceae (CRE) and vancomycin-resistant Enterococcus (VRE). Therefore, there is a dire need for new therapeutic agents that can mitigate the unbridled emergence of drug-resistant pathogens. In the present study, several benzoxazole-thiazolidinone hybrids (BT hybrids) were synthesized and evaluated for their antibacterial activity against the ESKAP pathogen panel. The preliminary screening revealed the selective and potent inhibitory activity of hydroxy BT hybrids against S. aureus with MIC ≤ 4 μg mL-1. Hydroxy compounds (BT25, BT26, BT18, BT12, and BT11) exhibited a good selectivity index (SI > 20), which were determined to be non-toxic to Vero cells. An engaging fact is that two compounds BT25 and BT26 showed potent activity against various clinically-relevant and highly drug resistant S. aureus (MRSA & VRSA) and Enterococcus (VRE) isolates. These hybrids showed concentration-dependent bactericidal activity that is comparable to vancomycin. These experimental results were corroborated with docking, molecular dynamics, and free energy studies to discern the antibacterial mechanisms of hydroxy BT hybrids with three bacterial enzymes DNA gyrase B, MurB, and penicillin binding protein 4 (PBP4). The reassuring outcome of the current investigation confirmed that the aforementioned BT hybrids could be used as very promisingly potent antibacterial agents for the treatment of Staphylococcus aureus and Enterococcus infections.

Segregation of Cry Genes in the Seeds Produced by F1 Bollgard® II Cotton Differs between Hybrids: Could This Be Linked to the Observed Field Resistance in the Pink Bollworm?

Indian populations of the Pink Bollworm (PBW) are resistant to Bt (Bacillus thuringiensis) cotton hybrids containing Cry1Ac and Cry2Ab genes. Segregation of these Cry genes in F1 hybrids could subject PBW to sublethal concentrations. Moreover, planting hybrids with varying zygosities of Cry genes could produce diverse segregation patterns and expose PBW populations to highly variable toxin concentrations. This could potentially promote the rate of resistance development. Therefore, we studied the segregation patterns of Cry genes in different commercial Bt hybrids cultivated in India. Results showed that two hybrids segregated according to the Mendelian mono-hybrid ratio, three segregated according to the Mendelian di-hybrid ratio, and one showed a mixed segregation pattern. The assortment of seeds containing Cry genes varied between bolls of the same hybrid. In India, different Bt cotton hybrids are cultivated in small patches next to each other, exposing PBW populations to sublethal doses and wide variations in the occurrence of Cry genes. It is necessary to avoid segregation of Cry genes in the seeds produced by F1 hybrids. This study recommends using Bt parents homozygous for Cry genes in commercial Bt cotton hybrid development. This breeding strategy could be effective for similar transgenic crop hybrids as well.

Effect of environment on combining ability, heterosis for seed cotton yield in Bt introgressed lines of upland cotton

AbstractSuccessful hybrid development work in cotton involves unearthing information of combining ability, heterosis and per se performance of the genetic material. This study involved multi‐environment estimation of combining ability and heterosis along with the stability of per se performance using Bt cotton genetic materials for seed cotton (Gossypium hirsutum L.) yield. Combining ability analysis across environments showed significant effects on the performance of genotypes, general combining ability (gca), specific combining ability (sca), genotype × environment, GCA × environment, and SCA × environment interactions. Combining ability variance revealed the predominance of nonadditive gene actions for seed cotton yield. The mean performance combining ability estimates were varied with the locations for parents as well as for hybrids. In a low yielding environment, the transgenic BGI parents, as well as hybrids, showed superior seed cotton yield levels compared with BGII or non‐Bt versions. There was a significant increase in heterosis noticed in BGII hybrids compared with BGI hybrids in a low yielding environment. The stability parameters showed significant genotype × environment variation and indicated that the stability of the genotype was mainly affected by the genetic background of the material. A positive association was noticed between per se performance and gca effects, heterobeltiosis and sca, and heterobeltiosis and mean of hybrids as the environment`s yield potential increased. The majority of the Bt hybrids showed positive heterosis over a better parent. Among the two versions of Bt transgenic cotton, BGI excelled in per se performance and gca and sca effects for seed cotton yield either in the homozygous form or hemizygous hybrids.

Performance of Bt maize event MON810 in controlling maize stem borers Chilo partellus and Busseola fusca in Uganda

Stem borers are major insect pests of maize in Uganda. A study was conducted in 2014–2016 to assess the performance of Bt hybrids expressing Cry1Ab (event MON810) against the two major stem borer species in Uganda – the African stem borer (Busseola fusca) and the spotted stem borer (Chilo partellus) – under artificial infestation. The study comprised 14 non-commercialized hybrids, including seven pairs of Bt and non-Bt hybrids (isolines), three non-Bt commercial hybrids and a conventional stem borer resistant check. All stem borer damage parameters (leaf damage, number of internodes tunneled and tunnel length) were generally significantly lower in Bt hybrids than in their isolines, the conventionally resistant hybrid, and local commercial hybrids. Mean yields were significantly higher by 29.4–80.5% in the Bt hybrids than in the other three categories of non-Bt hybrids. This study demonstrated that Bt maize expressing Cry1Ab protects against leaf damage and can limit entry of stem borers into the stems of maize plants, resulting in higher yield than in the non-transgenic hybrids. Thus, Bt maize has potential to contribute to the overall management package of stem borers in Uganda.

Additive Main Effects and Multiplicative Interaction for Seed Cotton Yield Performance and stability in Bt Cotton Hybrids (MON531 and MON15985)

A study was conducted to understand the stability of seed cotton yield of 105 Bt cotton hybrids (BGI and BGII) using Additive Main effects and Multiplicative Interactions (AMMI) analysis across three diverse locations in India during rainy season 2018. This study holds importance as the hybrids were resistant to Helicoverpa bollworms due to Bt events (MON531 and MON15985) in them which were expected to nullify variation arising out of differential bollworm pressure in different location, unlike in non Bt hybrids where this variation also played role in the stability of the hybrids. The main effect differences among hybrids (41.23 %), environments (39.56 %) and the interaction effects (19.21%) were highly significant of the total variance of seed cotton yield indicating a large difference between the testing location causing different hybrids to perform differently across the testing environments. The first two principal components axes (IPCA I and IPCA II) were highly significant and contributed 52.12 % and 47.88% of total interaction respectively. The distance from the origin and the placement of locations in different quadrants of biplot reflected that the locations were substantially discriminatory as Aurangabad and Dharwad, which were high yielding and Raichur was low yielding. Results showed that hybrids IAHH-8096 BGII, IAHH-8103 BGI, IAHH-8061 BGII and IAHH-8007 BGII were having lowest interaction and stable across the location, whereas hybrids IAHH-8080 BGI, IAHH-8084 BGI, IAHH-8004 BGII and IAHH-8105 BGI were having more interaction and unstable genotypes. Large frequency of hybrids (57) were stable with IPCA scores nearing zero and low ASV values which is attributed resistance to bollworm due to Bt events.

A 6-year field monitoring of fall armyworm, Spodoptera frugiperda, in transgenic Bt maize in Brazil

A 6-year field monitoring study was designed to compare the presence of fall armyworm Spodoptera frugiperda (J. E. Smith), leaf injury, its parasitoids, 100 seed weight, and seed yield of Bt maize hybrids approved for commercialization in the Brazilian market. Field trials were planted in two municipalities, divided into two periods, from 2011 to 2014 (period I), and due to the approval of different Bt hybrids, from 2015 to 2016 (period II). Treatments were Bt, non-Bt maize and all non-Bt maize sprayed with insecticide methomyl. Six Bt-maize hybrids were planted, expressing the following proteins: Cry1Ab, Cry1F, Cry1A.105 (Cry1Ab +Cry1Ac +Cry1F), Cry2Ab2a and Vip3. In 2015 and 2016 Bt Powercore was planted due to its commercial approval. The number of S. frugiperda larvae for most Bt hybrids was lower than on non-Bt hybrids, except for Fórmula TL and Herculex in period II, in both municipalities. In period I, Bt hybrids VT, VT 2 and Viptera showed almost no injury on their leaves, despite the high number of fall armyworm larvae found in plants. Different parasitoids emerged from larvae from Bt and non Bt hybrids: Archytas sp., Campoletis sp., Chelonus sp., Eiphosoma sp. and Ophion luteus. The average 100 seed weight was higher in municipality from Sete Lagoas for all Bt hybrids, non-Bt hybrids and non-Bt hybrids sprayed with methomyl, when compared to Nova Porteirinha during period I. Fórmula TL, non-Bt Fórmula TL sprayed with methomyl, and non-Bt Fórmula TL showed the lowest seed yield in both municipalities and periods.