Enhancing Integrated Pest Management in GM Cotton Systems Using Host Plant Resistance

Cotton plants overexpressing the Bacillus thuringiensis Cry23Aa and Cry37Aa binary-like toxins exhibit high resistance to the cotton boll weevil (Anthonomus grandis)

The cotton boll weevil (CBW, Anthonomus grandis) stands as one of the most significant threats to cotton crops (Gossypium hirsutum). Despite substantial efforts, the development of a commercially viable transgenic cotton event for effective open-field control of CBW has remained elusive. This study describes a detailed characterization of the insecticidal toxins Cry23Aa and Cry37Aa against CBW. Our findings reveal that CBW larvae fed on artificial diets supplemented exclusively with Cry23Aa decreased larval survival by roughly by 69%, while supplementation with Cry37Aa alone displayed no statistical difference compared to the control. However, the combined provision of both toxins in the artificial diet led to mortality rates approaching 100% among CBW larvae (LC50 equal to 0.26 PPM). Additionally, we engineered transgenic cotton plants by introducing cry23Aa and cry37Aa genes under control of the flower bud-specific pGhFS4 and pGhFS1 promoters, respectively. Seven transgenic cotton events expressing high levels of Cry23Aa and Cry37Aa toxins in flower buds were selected for greenhouse bioassays, and the mortality rate of CBW larvae feeding on their T0 and T1 generations ranged from 75% to 100%. Our in silico analyses unveiled that Cry23Aa displays all the hallmark characteristics of β-pore-forming toxins (β-PFTs) that bind to sugar moieties in glycoproteins. Intriguingly, we also discovered a distinctive zinc-binding site within Cry23Aa, which appears to be involved in protein-protein interactions. Finally, we discuss the major structural features of Cry23Aa that likely play a role in the toxin's mechanism of action. In view of the low LC50 for CBW larvae and the significant accumulation of these toxins in the flower buds of both T0 and T1 plants, we anticipate that through successive generations of these transgenic lines, cotton plants engineered to overexpress cry23Aa and cry37Aa hold promise for effectively managing CBW infestations in cotton crops.

Sequential and Simultaneous Interactions of Plant Allelochemical Flavone, Bt Toxin Vip3A, and Insecticide Emamectin Benzoate in Spodoptera frugiperda

Target pests of genetically engineered crops producing both defensive allelochemicals and Bacillus thuringiensis (Bt) toxins often sequentially or simultaneously uptake allelochemicals, Bt toxins, and/or insecticides. How the three types of toxins interact to kill pests remains underexplored. Here we investigated the interactions of Bt toxin Vip3A, plant allelochemical flavone, and insecticide emamectin benzoate in Spodoptera frugiperda. Simultaneous administration of flavone LC25 + Vip3A LC25, emamectin benzoate LC25 + Vip3A LC25, and flavone LC15 + emamectin benzoate LC15 + Vip3A LC15 but not flavone LC25 + emamectin LC25 yielded a mortality significantly higher than their expected additive mortality (EAM). One-day pre-exposure to one toxin at LC5 followed by six-day exposure to the same toxin at LC5 plus another toxin at LC50 showed that the mortality of flavone LC5 + Vip3A LC50, emamectin benzoate LC5 + Vip3A LC50, and Vip3A LC5 + emamectin benzoate LC50 were significantly higher than their EAM, while that of flavone LC5 + emamectin benzoate LC50 was significantly lower than their EAM. No significant difference existed among the mortalities of Vip3A LC5 + flavone LC50, emamectin benzoate LC5 + flavone LC50, and their EAMs. The results suggest that the interactions of the three toxins are largely synergistic (inductive) or additive, depending on their combinations and doses.

Categories of resistance in cotton genotypes, Gossypium spp. against cotton-melon aphid, Aphis gossypii (Hemiptera: Aphididae)

Cotton-melon aphid, Aphis gossypii Glover (Hemiptera: Aphididae), is emerging as a potential threat to cotton cultivation worldwide. The resistance categories in Gossypium arboreum to A. gossypii still need to be explored. We screened 87 G. arboreum and 20 Gossypium hirsutum genotypes against aphids under natural field conditions. Twenty-six selected genotypes from these 2 species were tested under glasshouse conditions for resistance categories (antixenosis, antibiosis, and tolerance). Resistance categories were assessed by no-choice antibiosis assay, free-choice aphid settling assay, cumulative aphid days using population buildup tests, chlorophyl loss index, and damage ratings. No-choice antibiosis experiment revealed that the G. arboreum genotypes GAM156, PA785, CNA1008, DSV1202, FDX235, AKA2009-6, DAS1032, DHH05-1, GAM532, and GAM216 had a significant adverse effect on aphid development time, longevity, and fecundity. Gossypium arboreum genotypes CISA111 and AKA2008-7 expressed a low level of antixenosis but possessed antibiosis and tolerance. Aphid resistance persisted uniformly at different plant developmental stages studied. The chlorophyl loss percentage and damage rating scores were lower in G. arboreum than in G. hirsutum genotypes, indicating the existence of tolerance in G. arboreum to aphids. Logical relations analysis of resistance contributing factors depicted the presence of antixenosis, antibiosis, and tolerance in the G. arboreum genotypes PA785, CNA1008, DSV1202, and FDX235, indicating their utility for evaluating the mechanisms of resistance and aphid resistance introgression breeding into G. hirsutum to develop commercially cultivated cotton lines.

A novel picorna-like virus identified in the cotton boll weevil Anthonomus grandis (Coleoptera: Curculionidae)

The cotton boll weevil (CBW; Anthonomus grandis; Coleoptera: Curculionidae) is considered the major insect pest of cotton, causing considerable losses in yield and fiber quality. An increase in the boll weevil population due to increasingly inefficient chemical control measures is of great concernamong cotton producers. The absence of conventional or transgenic cultivars with minimal resistance to CBW has stimulated the search for new molecular and biological tools for efficient control of this insect pest. In this study, we used a metagenomic approach based on RNA deep sequencing to investigate the presence of viruses and coding viral RNA in apparently healthy native adult CBW insects collected from cotton crops in Mato Grosso state, Brazil. Using an Illumina HiSeq 2000 paired-end platform, 138,798 virus-related reads were obtained, and a consensus sequence of a putative new virus, 10,632 nucleotides in length, was assembled. The sequences of the 5' and 3' untranslated regions (UTRs) were determined by rapid amplification of cDNA ends (RACE), followed by Nanopore sequencing. The complete genome sequence included a 5'-UTR (1,158 nucleotides), a 3'-UTR (561 nucleotides), and a single ORF of 8,913 nucleotides encoding a large polyprotein. Sequence analysis of the putative polyprotein showed several regions with high sequence similarity to structural and non-structural proteins of viruses of the family Iflaviridae. Pairwise alignments of polyprotein amino acid sequences showed the highest sequence identity (32.13%) to a partial polyprotein sequence of a putative iflavirus (QKN89051.1) found in samples from wild zoo birds in China. Phylogenetic analysis based on full polyprotein sequences of different iflaviruses indicated that this new picorna-like virus is most closely related to iflaviruses found in lepidopteran insects, and it was therefore tentatively named "Anthonomus grandis iflavirus 1" (AgIV-1). This is, to our knowledge, the first complete viral genome sequence found in CBW, and it could provide a basis for further studies about the infectivity and transmission of this virus and its possible association with symptoms or acute disease. AgIV-1 could potentially be used to develop biological or molecular tools, such as a viral vector to carry interfering RNA molecules for CBW control.

The Past, Present, and Future of Host Plant Resistance in Cotton: An Australian Perspective

Cotton is a key global fiber crop. However, yield potential is limited by the presence of endemic and introduced pests and diseases. The introduction of host plant resistance (HPR), defined as the purposeful use of resistant crop cultivars to reduce the impact of pests and diseases, has been a key breeding target for the Commonwealth Scientific and Industrial Research Organisation (CSIRO) cotton breeding program. The program has seen success in releasing cultivars resistant to Bacterial blight, Verticillium wilt, Fusarium wilt, and Cotton bunchy top. However, emerging biotic threats such as Black root rot and secondary pests, are becoming more frequent in Australian cotton production systems. The uptake of tools and breeding methods, such as genomic selection, high throughput phenomics, gene editing, and landscape genomics, paired with the continued utilization of sources of resistance from Gossypium germplasm, will be critical for the future of cotton breeding. This review celebrates the success of HPR breeding activities in the CSIRO cotton breeding program and maps a pathway for the future in developing resistant cultivars.

Discovery and functional characterization of novel cotton promoters with potential application to pest control

pGhERF105 and pGhNc-HARBI1 promoters are highly responsive to CBW infestation and exhibit strong activity in vegetative and reproductive tissues, increasing their potential application in GM crop plants for pest control. The main challenge to cotton (Gossypium hirsutum) crop productivity is the constant attack of several pests, including the cotton boll weevil (CBW, Anthonomus grandis), which uses cotton floral buds for feeding and egg-laying. The endophytic nature of the early developmental stages of CBW makes conventional pesticide-based control poorly efficient. Most biotechnological assets used for pest control are based on Bacillus thurigiensis insecticidal Cry toxins or the silencing of insect-pest essential genes using RNA-interference technology. However, suitable plant promoter sequences are required to efficiently drive insecticidal molecules to the target plant tissue. This study selected the Ethylene Responsive Factor 105 (GhERF105) and Harbinger transposase-derived nuclease (GhNc-HARBI1) genes based on available transcriptome-wide data from cotton plants infested by CBW larvae. The GhERF105 and GhNc-HARBI1 genes showed induction kinetics from 2 to 96 h under CBW's infestation in cotton floral buds, uncovering the potential application of their promoters. Therefore, the promoter regions (1,500 base pairs) were assessed and characterized using Arabidopsis thaliana transgenic plants. The pGhERF105 and pGhNc-HARBI1 promoters showed strong activity in plant vegetative (leaves and roots) and reproductive (flowers and fruits) tissues, encompassing higher GUS transcriptional activity than the viral-constitutive Cauliflower Mosaic Virus 35S promoter (pCaMV35S). Notably, pGhERF105 and pGhNc-HARBI1 promoters demonstrated more efficiency in driving reporter genes in flowers than other previously characterized cotton flower-specific promoters. Overall, the present study provides a new set of cotton promoters suitable for biotechnological application in cotton plants for pest resistance.

Cotton Breeding in Australia: Meeting the Challenges of the 21st Century

The Commonwealth Scientific and Industrial Research Organisation (CSIRO) cotton breeding program is the sole breeding effort for cotton in Australia, developing high performing cultivars for the local industry which is worth∼AU$3 billion per annum. The program is supported by Cotton Breeding Australia, a Joint Venture between CSIRO and the program's commercial partner, Cotton Seed Distributors Ltd. (CSD). While the Australian industry is the focus, CSIRO cultivars have global impact in North America, South America, and Europe. The program is unique compared with many other public and commercial breeding programs because it focuses on diverse and integrated research with commercial outcomes. It represents the full research pipeline, supporting extensive long-term fundamental molecular research; native and genetically modified (GM) trait development; germplasm enhancement focused on yield and fiber quality improvements; integration of third-party GM traits; all culminating in the release of new commercial cultivars. This review presents evidence of past breeding successes and outlines current breeding efforts, in the areas of yield and fiber quality improvement, as well as the development of germplasm that is resistant to pests, diseases and abiotic stressors. The success of the program is based on the development of superior germplasm largely through field phenotyping, together with strong commercial partnerships with CSD and Bayer CropScience. These relationships assist in having a shared focus and ensuring commercial impact is maintained, while also providing access to markets, traits, and technology. The historical successes, current foci and future requirements of the CSIRO cotton breeding program have been used to develop a framework designed to augment our breeding system for the future. This will focus on utilizing emerging technologies from the genome to phenome, as well as a panomics approach with data management and integration to develop, test and incorporate new technologies into a breeding program. In addition to streamlining the breeding pipeline for increased genetic gain, this technology will increase the speed of trait and marker identification for use in genome editing, genomic selection and molecular assisted breeding, ultimately producing novel germplasm that will meet the coming challenges of the 21st Century.

Core Collections: Is There Any Value for Cotton Breeding?

Global plant breeding activities are reliant on the available genetic variation held in extant varieties and germplasm collections. Throughout the mid- to late 1900s, germplasm collecting efforts were prioritized for breeding programs to archive precious material before it disappeared and led to the development of the numerous large germplasm resources now available in different countries. In recent decades, however, the maintenance and particularly the expansion of these germplasm resources have come under threat, and there has been a significant decline in investment in further collecting expeditions, an increase in global biosecurity restrictions, and restrictions placed on the open exchange of some commercial germplasm between breeders. The large size of most genebank collections, as well as constraints surrounding the availability and reliability of accurate germplasm passport data and physical or genetic characterization of the accessions in collections, limits germplasm utilization by plant breeders. To overcome these constraints, core collections, defined as a representative subset of the total germplasm collection, have gained popularity. Core collections aim to increase germplasm utilization by containing highly characterized germplasm that attempts to capture the majority of the variation in a whole collection. With the recent availability of many new genetic tools, the potential to unlock the value of these resources can now be realized. The Commonwealth Scientific and Industrial Research Organisation (CSIRO) cotton breeding program supplies 100% of the cotton cultivars grown in Australia. The program is reliant on the use of plant genetic resources for the development of improved cotton varieties to address emerging challenges in pest and disease resistance as well as the global changes occurring in the climate. Currently, the CSIRO germplasm collection is actively maintained but underutilized by plant breeders. This review presents an overview of the Australian cotton germplasm resources and discusses the appropriateness of a core collection for cotton breeding programs.

Inductive and synergistic interactions between plant allelochemical flavone and Bt toxin Cry1Ac in Helicoverpa armigera

Genetically engineered crops simultaneously produce defensive allelochemicals and Bacillus thuringiensis (Bt) toxin proteins to kill some of the world's most devastating insect pests. How the two types of toxins, when ingested sequentially or simultaneously, interact at both lethal and sublethal doses in these pests remains underexplored. Here, we examined the toxicological interactions between the Bt toxin Cry1Ac and the flavonoid allelochemical flavone in Helicoverpa armigera. Simultaneous exposure of H. armigera neonates to lethal doses (LC₂₅ ) of Cry1Ac and flavone caused a mortality significantly higher than that of either toxin alone and their expected additive mortality. Preexposure for 24 h to a sublethal dose (LC₁₀ ) of Cry1Ac followed by 6-d simultaneous exposure to the same dose of Cry1Ac plus a lethal dose (1.6 mg/g diets, LC₅₀ ) of flavone resulted in a mortality significantly higher than that of the LC₅₀ dose of flavone alone and the expected additive mortality of the LC₅₀ dose of flavone plus the LC₁₀ dose of Cry1Ac. One-day preexposure to the sublethal dose (LC₁₀ ) of flavone followed by 6-d simultaneous exposure to the LC₅₀ dose (6 ng/cm² ) of Cry1Ac plus the LC₁₀ dose of flavone yielded a mortality significantly higher than that of the LC₅₀ dose of Cry1Ac but similar to the expected additive mortality of the LC₅₀ dose of Cry1Ac plus the LC₁₀ dose of flavone. The results suggest that Cry1Ac induces and synergizes the toxicity of flavone against H. armigera larvae.

Establishment and Application of a Monitoring Strategy for Living Modified Cotton in Natural Environments in South Korea

Cotton (Gossypium hirsutum L.) is grown worldwide for its natural hollow fibers and is used as cattle feed. Living modified (LM) cotton is not cultivated in South Korea and must be imported for food, feed, and processing. From 2009 to 2013, the Ministry of Environment (MOE) and the National Institute of Ecology (NIE) conducted a natural environment monitoring and post-management initiative for living modified organisms (LMOs) in some areas to reduce the likelihood of harmful effects caused by unintentionally discharged LMOs during transportation and use. In this study, we adopted a new strategy to identify unintentionally released LM cotton plants nationwide from 2014 to 2018. A total of 451 suspicious cotton samples were collected from 3921 survey sites. Among them, we identified 255 LM cotton plants, of which approximately 72.2% had transgenic herbicide and insecticide traits. The majority of the samples were collected from the roadside along transportation routes and from stockbreeding farms. This study establishes an LMO safety management system to efficiently maintain conservation efforts in South Korea. Our findings suggest that these efforts may play a key role in safely transporting, using, and managing approved LMOs, as well as in regulating unintentionally released LMOs, in order to preserve the natural ecosystem of South Korea.

Pyramiding of cry toxins and methanol producing genes to increase insect resistance in cotton

The idea of enhanced methanol production from cell wall by pectin methyl esterase enzymes (PME) combined with expression of cry genes from Bacillus thuringiensis as a strategy to improve insect pest control in cotton is presented. We constructed a cassette containing two cry genes (cry1Fa and Cry32Aa) and two pme genes, one from Arabidopsis thaliana (AtPME), and other from Aspergillus. niger (AnPME) in pCAMBIA1301 plant expression vector using CAMV-35S promoter. This construction was transformed in Eagle-2 cotton variety by using shoot apex-cut Agrobacterium-mediated transformation. Expression of cry genes and pme genes was confirmed by qPCR. Methanol production was measured in control and in the cry and pme transformed plants showing methanol production only in transformed plants, in contrast to the non-transgenic cotton plants. Finally, insect bioassays performed with transgenic plants expressing cry and pme genes showed 100% mortality for Helicoverpa armigera (cotton bollworm) larvae, 70% mortality for Pectinophora gossypiella (pink bollworm) larvae and 95% mortality of Earias fabia, (spotted bollworm) larvae, that was higher than the transgenic plants expressing only cry genes that showed 84%, 49% and 79% mortality, respectively. These results demonstrate that Bt. cry-genes coupled with pme genes are an effective strategy to improve the control of different insect pests.

Bacterial Microbiota of Field-Collected Helicoverpa zea (Lepidoptera: Noctuidae) from Transgenic Bt and Non-Bt Cotton

The bollworm, Helicoverpa zea (Boddie) (Lepidoptera: Noctuidae), is an important agricultural pest in U.S. cotton and is managed using transgenic hybrids that produce insecticidal proteins from the bacterium, Bacillus thuringiensis (Bt). The reduced efficacy against H. zea caterpillars of Bt plants expressing Cry toxins is increasing in the field. In a first step towards understanding Bt cotton–bollworm–microbiota interactions, we investigated the internal bacterial microbiota of second–third stadium H. zea collected in the field from non-Bt versus Bt (WideStrike) cotton in close proximity (in North Carolina, USA). The bacterial populations were analyzed using culture-dependent and -independent molecular approaches. We found that WideStrike samples had a higher bacterial density and diversity per larva than insects collected from non-Bt cotton over two field seasons: 8.42 ± 0.23 and 5.36 ± 0.75 (log₁₀ colony forming units per insect) for WideStrike compared to 6.82 ± 0.20 and 4.30 ± 0.56 for non-Bt cotton for seasons 1 and 2, respectively. Fifteen phyla, 103 families, and 229 genera were identified after performing Illumina sequencing of the 16S rRNA. At the family level, Enterobacteriaceae and Enterococcaceae were the most abundant taxa. The Enterococcaceae family was comprised mostly of Enterococcus species (E. casseliflavus and another Enterococcus sp.). Members of the Enterococcus genus can acidify their environment and can potentially reduce the alkaline activation of some Bt toxins. These findings argue for more research to better understand the role of cotton–bollworm–bacteria interactions and the impact on Bt toxin caterpillar susceptibility.

Distinct defensive activity of phenolics and phenylpropanoid pathway genes in different cotton varieties toward chewing pests

Identifying the maximum level of inherent defense against harmful insects in natural variation among wild lineages of crop plants may result in high yield tolerant varieties and reducing use of chemical insecticides. However, knowledge of natural cotton genotypes with high insect-resistance is still indistinguishable at the biochemical or molecular level. In the present study, different cultivated Gossypium hirsutum varieties were evaluated for their inherent insect-tolerance against two major cottons chewing pests. The insect bio-assay identified two tolerant and one susceptible cotton varieties. The study demonstrates difference in phenolic acids, proanthocyanidin and tannin accumulation in tolerant and susceptible varieties. The post-infestation of chewing pests increases transcript level of the phenylpropanoid pathway genes were detected in tolerant varieties as compared to the susceptible varieties. Altogether, chewing pest-tolerance level in cotton varieties is the cumulative effect of enhanced phenylpropanoid pathway genes expression and secondary metabolite leading to defense responses to conventional host plant.

Constitutive and induced insect resistance in RNAi-mediated ultra-low gossypol cottonseed cotton

BACKGROUND

Besides fibers, cotton plants also produce a large amount of seeds with a high oil and protein content. The use of these seeds is restricted by their high contents of the terpenoid gossypol, which is harmful to humans and livestock. Using a genetic engineering approach, "Ultra-low gossypol cottonseed" (ULGCS) plants were produced by knocking down an enzyme that catalyzes the formation of a precursor of gossypol. This was accomplished via RNAi-mediated silencing of the target gene using a seed-specific α-globulin promotor. Since gossypol is also a crucial defense mechanism against leaf-feeding herbivores, ULGCS plants might possess lower herbivore resistance than non-engineered plants. Therefore, we tested the constitutive and inducible direct insect resistance of two ULGCS cotton lines against the African cotton leafworm, Spodoptera littoralis.

RESULT

The herbivore was equally affected by both ULGCS lines and the control (Coker 312) line when feeding on fully expanded true leaves from undamaged plants and plants induced by jasmonic acid. When plants were induced by caterpillar-damage, however, S. littoralis larvae performed better on the ULGCS plants. Terpenoid analyses revealed that the ULGCS lines were equally inducible as the control plants. Levels of terpenoids were always lower in one of the two lines. In the case of cotyledons, caterpillars performed better on ULGCS cotton than on conventional cotton. This was likely caused by reduced levels of gossypol in ULGCS cotyledons.

CONCLUSION

Despite those effects, the insect resistance of ULGSC cotton can be considered as largely intact and the plants may, therefore, be an interesting alternative to conventional cotton varieties.

The impact of Genetically Modified (GM) crops in modern agriculture: A review

Genetic modification in plants was first recorded 10,000 years ago in Southwest Asia where humans first bred plants through artificial selection and selective breeding. Since then, advancements in agriculture science and technology have brought about the current GM crop revolution. GM crops are promising to mitigate current and future problems in commercial agriculture, with proven case studies in Indian cotton and Australian canola. However, controversial studies such as the Monarch Butterfly study (1999) and the Séralini affair (2012) along with current problems linked to insect resistance and potential health risks have jeopardised its standing with the public and policymakers, even leading to full and partial bans in certain countries. Nevertheless, the current growth rate of the GM seed market at 9.83-10% CAGR along with promising research avenues in biofortification, precise DNA integration and stress tolerance have forecast it to bring productivity and prosperity to commercial agriculture.

Plant training for induced defense against insect pests: a promising tool for integrated pest management in cotton

Enhancing cotton pest management using plant natural defenses has been described as a promising way to improve the management of crop pests. We here reviewed various studies on cotton growing systems to illustrate how an ancient technique called plant training, which includes plant topping and pruning, may contribute to this goal. Using examples from cotton crops, we show how trained plants can be brought to a state of enhanced defense that causes faster and more robust activation of their defense responses. We revisit the agricultural benefits associated with this technique in cotton crops, with a focus on its potential as a supplementary tool for integrated pest management (IPM). In particular, we examine its role in mediating plant interactions with conspecific neighboring plants, pests and associated natural enemies. We propose a new IPM tool, plant training for induced defense, which involves inducing plant defense through artificial injury. Experimental evidence from various studies shows that cotton training is a promising technique, particularly for smallholders, which can be used as part of an IPM program to significantly reduce insecticide use and to improve productivity in cotton farming. © 2018 Society of Chemical Industry.

Laccase GhLac1 Modulates Broad-Spectrum Biotic Stress Tolerance via Manipulating Phenylpropanoid Pathway and Jasmonic Acid Synthesis

Plants are constantly challenged by a multitude of pathogens and pests, which causes massive yield and quality losses annually. A promising approach to reduce such losses is to enhance the immune system of plants through genetic engineering. Previous work has shown that laccases (p-diphenol:dioxygen oxidoreductase, EC 1.10.3.2) function as lignin polymerization enzymes. Here we demonstrate that transgenic manipulation of the expression of the laccase gene GhLac1 in cotton (Gossypium hirsutum) can confer an enhanced defense response to both pathogens and pests. Overexpression of GhLac1 leads to increased lignification, associated with increased tolerance to the fungal pathogen Verticillium dahliae and to the insect pests cotton bollworm (Helicoverpa armigera) and cotton aphid (Aphis gosypii). Suppression of GhLac1 expression leads to a redirection of metabolic flux in the phenylpropanoid pathway, causing the accumulation of JA and secondary metabolites that confer resistance to V. dahliae and cotton bollworm; it also leads to increased susceptibility to cotton aphid. Plant laccases therefore provide a new molecular tool to engineer pest and pathogen resistance in crops.

Current perspectives on genetically modified crops and detection methods

Genetically modified (GM) crops are the fastest adopted commodities in the agribiotech industry. This market penetration should provide a sustainable basis for ensuring food supply for growing global populations. The successful completion of two decades of commercial GM crop production (1996-2015) is underscored by the increasing rate of adoption of genetic engineering technology by farmers worldwide. With the advent of introduction of multiple traits stacked together in GM crops for combined herbicide tolerance, insect resistance, drought tolerance or disease resistance, the requirement of reliable and sensitive detection methods for tracing and labeling genetically modified organisms in the food/feed chain has become increasingly important. In addition, several countries have established threshold levels for GM content which trigger legally binding labeling schemes. The labeling of GM crops is mandatory in many countries (such as China, EU, Russia, Australia, New Zealand, Brazil, Israel, Saudi Arabia, Korea, Chile, Philippines, Indonesia, Thailand), whereas in Canada, Hong Kong, USA, South Africa, and Argentina voluntary labeling schemes operate. The rapid adoption of GM crops has increased controversies, and mitigating these issues pertaining to the implementation of effective regulatory measures for the detection of GM crops is essential. DNA-based detection methods have been successfully employed, while the whole genome sequencing using next-generation sequencing (NGS) technologies provides an advanced means for detecting genetically modified organisms and foods/feeds in GM crops. This review article describes the current status of GM crop commercialization and discusses the benefits and shortcomings of common and advanced detection systems for GMs in foods and animal feeds.