The scale of the screening effort is what sets the work apart. Rather than studying a handful of lines, the team, led by Jie Zhao and Yingjun Zhang at the Hebei Academy of Agriculture and Forestry Sciences in Shijiazhuang, assessed herbicide damage across a diverse panel of 539 common wheat accessions. Each plant received a herbicide damage rating after treatment, and the researchers then searched the wheat genome for single-letter DNA variants that statistically tracked with tolerance or susceptibility. This approach, known as a genome-wide association study or GWAS, exploits the natural genetic variation already present in a crop species, scanning millions of genetic markers for those that co-inherit with the trait of interest.

The scan converged on four stable genetic loci, designated QMSL-3D.1, QMSL-4A.1, QMSL-5A.1/QMSH-5A.1, and QMSL-5B.1, located on chromosomes 3D, 4A, 5A, and 5B respectively. The naming convention reflects their role as quantitative trait loci for mesosulfuron-methyl response, with the letter suffixes indicating the chromosome arm. Stability across testing conditions matters enormously in GWAS work, because spurious associations often appear in one environment and vanish in another. Loci that hold up across multiple treatments and assessments are far more likely to harbor genuine causal genes rather than statistical noise.

One of the most striking findings concerns what happens when breeders stack the favorable versions of these loci together. The researchers found that pyramiding the superior alleles at all four loci reduced the mean herbicide damage rating by 32.1 percent under one mesosulfuron-methyl dosage and by 26.6 percent under a second. Those are meaningful reductions in crop injury. Yet the team was careful to note that these alleles collectively explained only a minor proportion of the overall phenotypic variation. In other words, tolerance to this herbicide is a polygenic trait, shaped by many genes of small effect scattered across the genome, and the four loci represent an important but incomplete slice of that genetic architecture.

To get closer to the actual genes, the researchers turned to transcriptomics, sequencing the RNA produced by a tolerant cultivar called Chang 4640 and a susceptible cultivar called Xinong 928 under herbicide treatment. The logic is straightforward: if a gene near an associated locus behaves differently in tolerant versus susceptible plants when the herbicide is applied, it becomes a prime suspect for the causal variant. The comparison flagged two differentially expressed candidate genes, TraesCS5A02G398300 and TraesCS5B02G403400, sitting within the chromosome 5A and 5B loci.

What those two genes do makes the story biologically compelling. They are homoeologous genes, meaning they are paired copies inherited from the ancestral grass genomes that fused to form modern hexaploid wheat, which carries three related versions of most genes across its A, B, and D subgenomes. Both copies encode aspartate-semialdehyde dehydrogenase, a key enzyme in the biosynthesis of essential amino acids. The connection to herbicide tolerance is not accidental. Mesosulfuron-methyl belongs to the sulfonylurea class, which kills plants by inhibiting acetolactate synthase, the first enzyme dedicated to branched-chain amino acid synthesis. A wheat plant with more robust capacity to sustain amino acid production under chemical stress plausibly withstands the treatment better, and the transcriptomic evidence places the enzyme squarely in the plant’s response to the herbicide.

Translating the discovery into breeding practice required a second layer of technology. The team developed six Kompetitive Allele-Specific PCR markers, or KASP markers, closely linked to the tolerance loci and candidate genes. KASP genotyping is a fluorescence-based assay that distinguishes DNA variants cheaply and quickly, making it well suited to high-throughput breeding programs. With these markers, a breeder can test seedlings in a lab within days and know which carry the tolerance alleles, without waiting for a growing season of herbicide spraying to reveal the answer. This is the essence of marker-assisted selection, and it converts a slow, weather-dependent screening process into a routine molecular test.

The study also looked beyond genetics to practical variety performance. In field evaluations conducted across multiple years and at several mesosulfuron-methyl concentrations, the researchers screened wheat varieties for consistent tolerance and identified five varieties that maintained stable tolerance under the tested conditions. Multi-year, multi-dose validation is critical because herbicide injury is notoriously sensitive to environmental conditions; a variety that tolerates the chemical in one season may fail in another if the underlying genetics are weak or the expression is environmentally unstable. The five identified varieties provide immediate, field-proven material for growers and for crossing programs alike.

The agricultural context gives the work its urgency. Grassy weeds such as ryegrass and other poaceae relatives are among the most damaging competitors in wheat fields because they mimic the crop’s growth habit and are hardest to control selectively. Mesosulfuron-methyl is prized precisely because it exploits the narrow biochemical differences between wheat and its grassy weed competitors. But improper application can tip the balance the wrong way, producing phytotoxicity and yield losses in the crop itself. Herbicide-resistant weed populations are also an escalating global problem, with documented cases of metabolic resistance and altered target-site sensitivity in multiple weed species, which makes protecting the efficacy of remaining effective chemistries a priority. Tolerant wheat varieties would give farmers a wider safety margin, allowing recommended or slightly variable doses to be applied without fear of crop injury.

The study’s authors are candid that the four loci explain only part of the tolerance puzzle, and the candidate genes remain candidates until formal validation, for example through knockout or overexpression experiments, confirms their causal role. Still, the resources generated here, from the 539-accession association panel to the KASP markers and the transcriptomic dataset, constitute a launchpad for that next phase. The work was supported by the National Natural Science Foundation of China and other national and provincial programs, reflecting the strategic importance of wheat breeding in a major wheat-producing region. For a crop that feeds roughly a third of humanity, even incremental gains in the reliability of weed control translate into substantial yield protection, and this study has turned a poorly understood trait into a set of concrete, testable, and breedable genetic targets.

Subject of Research: Genetic loci and candidate genes associated with mesosulfuron-methyl herbicide tolerance in wheat

Article Title: Genome-wide association study and transcriptome analysis reveal candidate genes associated with mesosulfuron-methyl tolerance in wheat

Article References: Zhao, J., Cai, M., Sun, L., Hu, M., Li, H., Liu, X., & Zhang, Y. (2026). Genome-wide association study and transcriptome analysis reveal candidate genes associated with mesosulfuron-methyl tolerance in wheat. Theoretical and Applied Genetics, 139(11), Article 306. https://doi.org/10.1007/s00122-026-05411-6

Image Credits: AI Generated

DOI: 10.1007/s00122-026-05411-6

Keywords: wheat, mesosulfuron-methyl, herbicide tolerance, GWAS, quantitative trait loci, transcriptomics, aspartate-semialdehyde dehydrogenase, KASP markers, marker-assisted selection, plant breeding, sulfonylurea herbicides, crop genetics

The target of the work was 4-hydroxyphenylpyruvate dioxygenase, or HPPD, an enzyme that sits at a critical junction in plant metabolism. HPPD catalyzes a step in the breakdown of tyrosine that feeds the production of homogentisate, a precursor required for plastoquinone and tocopherol synthesis. Plastoquinone, in turn, is essential for carotenoid biosynthesis, and carotenoids protect the photosynthetic machinery of chloroplasts from oxidative damage. This dependency is exactly what makes HPPD such an effective herbicidal target: compounds that inhibit the enzyme, including widely used triketone herbicides such as mesotrione, starve plants of carotenoids, causing bleaching of newly emerged tissue and ultimately death. Weeds, crops, and everything green in between share this vulnerability, which is why engineering tolerance at the HPPD locus has long been an attractive but difficult proposition.

The difficulty lies in a classic trade-off. Mutations in the coding sequence of HPPD that weaken herbicide binding tend also to compromise the enzyme’s catalytic performance, because the herbicide-binding pocket overlaps with the chemistry the enzyme must perform. A plant carrying such a mutation may survive spraying, but it pays a growth penalty. Conversely, simply cranking up expression of an unmodified HPPD gene can raise the amount of enzyme available and dilute the herbicide’s effect, but regulatory overexpression often brings pleiotropic problems — metabolic imbalance, developmental defects, and unpredictable performance across genetic backgrounds and environments. The research team behind the new study recognized that dosage-sensitive traits like herbicide tolerance demand simultaneous optimization of both protein function and protein abundance.

Their solution was a dual-layer strategy. On the first layer, they used structure-guided protein design to identify amino acid substitutions in HPPD that would reduce sensitivity to herbicide inhibitors while preserving catalytic activity. Rather than screening random mutagenesis libraries, the researchers reasoned from the three-dimensional structure of the enzyme, focusing on positions that line the inhibitor-binding site but sit at a tolerable distance from the catalytic machinery. This rational approach, informed by computational tools for protein engineering that integrate structural and evolutionary constraints — an area that has advanced rapidly with artificial-intelligence-based inverse-folding models — allowed them to prioritize a small set of candidate substitutions with a high probability of decoupling inhibitor binding from enzymatic function.

On the second layer, the team turned to cis-regulatory engineering at the endogenous HPPD locus. Instead of inserting a transgene under a strong constitutive promoter, they edited the native promoter and regulatory regions of the crop’s own HPPD gene to tune its expression upward in the tissues where tolerance matters most. Because the edits were made in cis, at the gene’s natural address in the genome, the resulting plants carry modified versions of their own gene rather than foreign DNA constructs. This endogenous approach matters both scientifically and commercially: it preserves native regulation as much as possible, reduces the risk of position effects and silencing that plague transgenic insertions, and may ease the regulatory and public-acceptance pathways for edited crops in jurisdictions that distinguish gene-edited from transgenic plants.

Neither layer alone was sufficient. Coding-sequence edits that conferred reduced herbicide sensitivity produced plants whose tolerance was real but incomplete, while regulatory edits alone raised enzyme levels without addressing the fundamental vulnerability of the wild-type protein to inhibition. It was the combination — an enzyme variant less easily poisoned, produced at elevated levels from its own tuned promoter — that produced the striking tolerance phenotypes. The authors describe these combined versions as elite alleles: single, precisely defined haplotypes at the native locus that deliver a trait at a level useful for breeding, without the need for transgenes or multi-gene stacks.

Demonstrating the strategy in both rice and wheat is a significant part of the result. Rice, a model grass with a compact genome and efficient editing protocols, served as the development platform, but wheat presents a far harder engineering challenge because of its large polyploid genome, in which multiple homoeologous copies of genes must often be edited in concert to see an effect. That the dual-layer approach transferred between these two species suggests it is not a quirk of one crop’s genetics but a generalizable design principle for engineering dosage-sensitive traits — traits whose performance depends on getting both the quality and the quantity of a gene product right.

The implications extend well beyond herbicide tolerance. Herbicide-resistant weeds are a mounting global problem, documented across hundreds of species and virtually every major herbicide class, and new tolerance traits are needed both to replace overused chemistries and to enable rotation between different modes of action — a practice that slows the evolution of resistance in weed populations. An HPPD-based tolerance allele generated by editing native sequences could be introduced into elite breeding lines by conventional crossing once created in a donor background, or recreated directly in elite germplasm by editing, dramatically shortening the path from discovery to farmers’ fields compared with transgenic trait development.

More broadly, the study offers a template for how genome editing in crops is maturing. Early editing work largely mimicked loss-of-function genetics, knocking out genes to study their roles or eliminate undesirable traits. The frontier is now precision gain-of-function engineering: redesigning proteins in place, tuning their expression from native regulatory landscapes, and combining these edits into coherent alleles that behave predictably. The same dual-layer logic could apply to other dosage-sensitive agricultural targets, including disease resistance genes, nutrient biosynthetic pathways, and tolerance to drought, salinity, or heat, where both the biochemical properties of a protein and the amount of it a tissue produces determine the phenotype.

Challenges remain before elite HPPD alleles reach commercial reality. Edited crops must clear regulatory review in each market, and the agronomic performance of tolerance alleles must be validated across seasons, soils, and herbicide application regimes. Fitness costs of modified enzyme variants, if any, will need to be quantified over full crop lifecycles, and stewardship plans will be required to manage resistance evolution in weed populations exposed to HPPD-inhibiting chemistry. Yet the conceptual advance is clear and consequential: by treating a gene’s coding sequence and its regulatory architecture as a single coordinated design problem, plant biologists have shown that traits once requiring transgenic stacks can be built into the crop’s own genome, one precisely placed edit at a time. For a world that needs higher yields on finite land under intensifying weed pressure, that is a blueprint worth watching closely.

Subject of Research: Dual-layer genome editing of coding and cis-regulatory sequences at the HPPD locus to engineer herbicide-tolerant rice and wheat

Article Title: Coordinated editing of coding and regulatory sequences creates elite herbicide-tolerant alleles

Article References: Coordinated editing of coding and regulatory sequences creates elite herbicide-tolerant alleles. (2026). Nature Plants. https://doi.org/10.1038/s41477-026-02426-1 (Author names are not included in the publisher’s citation export.)

Image Credits: AI Generated

DOI: 10.1038/s41477-026-02426-1

Keywords: genome editing, herbicide tolerance, HPPD, rice, wheat, cis-regulatory engineering, protein design, crop breeding, gene editing, plant biotechnology, elite alleles, Nature Plants

The target of the engineering campaign was 4-hydroxyphenylpyruvate dioxygenase, or HPPD, an enzyme that sits at a critical junction in plant metabolism. HPPD catalyzes a key step in the tyrosine degradation pathway, converting 4-hydroxyphenylpyruvate into homogentisate, which in turn feeds the production of plastoquinone and tocopherols. Because plastoquinone is indispensable for carotenoid biosynthesis and for protecting the photosynthetic apparatus, blocking HPPD with herbicides such as mesotrione, isoxaflutole and fenpyrazone causes treated plants to bleach and die. This vulnerability makes HPPD inhibitors among the most valuable weed killers in modern agriculture, but it also means that any crop engineered to tolerate them must maintain a delicately balanced enzyme that still performs its metabolic duties while refusing to bind the herbicide.

Previous attempts to generate herbicide-tolerant HPPD variants relied largely on directed evolution, randomly mutating the gene and screening survivors for resistance. That approach can find resistance mutations, but it offers no guarantee that the resulting enzyme retains full catalytic activity, and it typically operates on a single genetic axis: the protein sequence itself. The Gao laboratory chose a fundamentally different route, beginning with structure. The team solved the crystal structure of rice HPPD, OsHPPD, depositing it in the Protein Data Bank under accession 21WF, and used the three-dimensional map of the enzyme to identify amino acid positions where substitutions could plausibly disrupt herbicide binding while leaving the catalytic machinery untouched. This structure-guided design narrowed the search space dramatically, focusing attention on residues near the herbicide-binding pocket rather than across the entire protein.

The structural analysis pointed to a cluster of glycine residues and a phenylalanine at position 378 as prime candidates. The researchers designed a panel of coding variants, including F378A, G414A, G415V and a series of substitutions at position 417, each chosen because the atomic geometry suggested the mutation would either enlarge or reshape the herbicide-binding cavity without disturbing the iron-coordinating active site or the substrate-channeling architecture of the enzyme. Biochemical assays confirmed the logic: the engineered enzymes retained their dioxygenase activity against the natural substrate while showing markedly reduced sensitivity to mesotrione, the HPPD-inhibiting herbicide used as the primary test compound throughout the study.

Installing these mutations in the rice genome required precision rather than brute force. The team deployed prime editing, a CRISPR-derived technology that uses a modified Cas9 fused to a reverse transcriptase and an extended guide RNA carrying the desired edit, to write the designed substitutions directly into the endogenous OsHPPD locus. Prime editing was chosen over conventional CRISPR-Cas9 knockout approaches because it makes exact sequence changes without creating double-strand DNA breaks, avoiding the large deletions, rearrangements and chromosomal damage that have been documented as unintended consequences of break-based editing. Using both standard pegRNA vectors and engineered epegRNA systems, the researchers generated transgene-free rice lines carrying each of the designed resistance alleles, confirming the edits by Sanger sequencing and verifying that the plants grew normally in the absence of herbicide.

The coding mutations alone conferred meaningful tolerance, but the team suspected that a second lever could push resistance to a level that would survive real-world field conditions. Their attention turned to cis-regulatory DNA, the non-coding sequences that govern how strongly a gene is expressed. Drawing on expression-modulating elements, short enhancer-like motifs that can boost transcription when placed near a promoter, the researchers screened candidate sequences in rice protoplasts using a dual-luciferase reporter assay. One sequence stood out: a compact 22-base-pair element, dubbed EME, that significantly increased expression when inserted upstream of the OsHPPD core promoter and 5-prime untranslated region. Computational analysis with the PlantPAN 4.0 database predicted that the element recruits transcription factors capable of amplifying gene activity, and RNA-folding simulations suggested the short sequence adopts a defined secondary structure that may facilitate its integration during prime editing.

The mechanism of EME insertion is itself a technical tour de force. The 22-base-pair element contains a palindromic sequence, meaning it reads the same in both directions, and the researchers showed that during the flap-equilibration step of prime editing this palindrome can exist either as a linear strand, producing a precise replacement, or as a structured three-prime flap whose microhomology with the genomic target allows flexible insertion. By tuning the editing system, including the use of an enhanced prime editor called ePPEplus, the team achieved efficient installation of the EME at the OsHPPD locus in whole plants, generating alleles that combined a resistance mutation in the coding region with an expression-boosting element in the regulatory region, all within a single gene and without any foreign DNA.

The results were striking. Rice plants carrying both layers of engineering, a resistance mutation such as G417A or G414A plus the EME element, showed elevated OsHPPD mRNA and protein abundance and tolerated mesotrione at rates up to four times the recommended field application dose. The plants also withstood isoxaflutole and fenpyrazone, demonstrating that the tolerance extends across the HPPD-inhibitor class rather than being specific to a single chemistry. Crucially, multi-season field trials in Hainan, China, in 2025 and 2026 showed that the engineered lines matched or exceeded wild-type plants in every major agronomic trait measured, including plant height, grain number per panicle, seed-setting rate, thousand-grain weight, tiller number and grain yield per plant. The absence of yield penalties is the detail that separates this work from many earlier trait-engineering efforts, where resistance often came at the cost of vigor.

To test whether the framework was a rice-specific trick or a general principle, the team turned to wheat, a hexaploid crop whose genome carries three homoeologous copies of the HPPD gene, TaHPPD-A1, TaHPPD-B1 and TaHPPD-D1. Multiplex prime editing was used to introduce glycine-to-alanine substitutions at the positions corresponding to rice G414 across all three homoeologs, and a duplicated EME element was then inserted into the regulatory region of one TaHPPD-B1 allele. The resulting wheat plants, designated 2EME-G404A, showed increased TaHPPD transcript and protein levels and enhanced mesotrione tolerance relative to plants carrying only the coding mutation. The demonstration that the dual-layer strategy functions in a polyploid genome, with its added complexity of multiple gene copies and larger regulatory landscapes, is strong evidence that the approach can be ported across species and genome architectures.

Beyond herbicide tolerance, the study articulates a template that the authors argue is broadly applicable to crop improvement. Most engineered traits to date have manipulated either a protein or a regulatory element, and the single-axis approach often hits a ceiling: a resistance enzyme may be too weak, or an overexpressed wild-type enzyme may still be inhibited. By coordinating structure-guided protein design with precise cis-regulatory tuning at the same locus, the dual-layer framework allows each layer to compensate for the limitations of the other, producing alleles that are simultaneously resistant and abundantly expressed. The strategy also sidesteps the transgene silencing, position effects and regulatory burdens associated with inserting foreign genes, because every change is written into the crop’s own DNA. With deep-sequencing data deposited under NCBI BioProject PRJNA1417282 and analysis code released through GitHub, the work provides both the biological blueprint and the computational toolkit for breeding programs seeking to engineer durable, penalty-free traits in the crops that feed the world.

Subject of Research: Dual-layer genome editing of HPPD coding and regulatory sequences to engineer herbicide-tolerant rice and wheat

Article Title: Coordinating structure-guided design and cis-regulatory optimization to engineer elite herbicide-tolerance alleles in crops

Article References: Zhang, R., Chai, Z., Wang, M., Chen, S., Liu, M., Shi, X., Zhang, C., Wang, W., Zhang, F., Wang, G., Lei, G., Chen, Y., & Gao, C. (2026). Coordinating structure-guided design and cis-regulatory optimization to engineer elite herbicide-tolerance alleles in crops. Nature Plants. https://doi.org/10.1038/s41477-026-02423-4

Image Credits: AI Generated

DOI: 10.1038/s41477-026-02423-4

Keywords: genome editing, prime editing, herbicide tolerance, HPPD, rice, wheat, cis-regulatory elements, mesotrione, crop breeding, protein design, CRISPR, plant biotechnology

The research, published in the Journal of Agriculture and Food Research, was led by Keisuke Soga and colleagues at Japan’s National Institute of Health Sciences and collaborating institutions. The team took soybean samples that had previously been analyzed for herbicide residues and subjected the very same material to a battery of event-specific real-time PCR tests. Their goal was exploratory but ambitious: to see whether the residue profile of glyphosate, glufosinate, and their metabolites could be matched to particular herbicide-tolerance traits in commercially distributed soybeans imported from the United States and Brazil.

The logic behind the approach rests on the biochemistry of herbicide tolerance. Glyphosate kills plants by inhibiting 5-enolpyruvylshikimate-3-phosphate synthase, or EPSPS, an enzyme essential for synthesizing aromatic amino acids through the shikimate pathway. Glyphosate-tolerant soybeans evade this attack by carrying a modified epsps gene, such as the cp4 epsps gene borrowed from the soil bacterium Agrobacterium tumefaciens strain CP4, which produces an enzyme the herbicide cannot bind. Glufosinate works differently: it blocks glutamine synthetase, causing toxic ammonia to accumulate and shutting down photosynthesis. Soybeans tolerate glufosinate by carrying the pat or bar gene, which encodes phosphinothricin N-acetyltransferase, an enzyme that acetylates the herbicide into N-acetyl-glufosinate, an inactive compound that no longer threatens the plant.

These mechanisms create a chemical fingerprint. A soybean carrying a modified epsps gene can survive glyphosate spraying and may retain detectable glyphosate residues, but it cannot convert glufosinate into its acetylated form. Conversely, a soybean carrying pat can metabolize glufosinate into N-acetyl-glufosinate, so the presence of that metabolite hints at a pat-containing event. The Japanese team reasoned that detecting glyphosate or the acetylated glufosinate metabolite in a shipment should statistically correlate with the presence of the corresponding transgenes, and that the strength of the correlation might even reveal which specific events dominate cultivation in the exporting country.

The sample set consisted of fifteen soybean lots: one edible soybean sample grown in Japan, eight feed samples from the United States, three non-GM samples from the United States imported under identity-preserved handling, and three feed samples from Brazil. Identity-preserved systems segregate non-GM soybeans from GM ones through documentation and traceability, though they cannot guarantee the complete absence of unintended commingling. The researchers ground 100 grams of each sample in a cryogenic mill, extracted genomic DNA, and screened for eleven GM events using primers and probes drawn from the European Union’s GMOMETHODS database and Japanese official detection methods, with the soybean lectin gene serving as an endogenous reference.

The qualitative results were striking. In the non-GM samples, GM events were essentially undetectable, with only a faint signal for event DAS-44406 in one sample. In the American feed samples, the team detected RRS, MON89788, FG72, A2704-12, A5547-127, and DAS-44406, while Brazilian feed samples were dominated by RRS, MON89788, and DAS-81419. The edible Japanese sample contained none of the tested events. Crucially, the events found in the herbicide-positive samples matched the residue chemistry: glyphosate-containing lots carried high levels of epsps-harboring events, and lots containing N-acetyl-glufosinate carried high levels of pat-harboring events.

Quantification sharpened the picture considerably. In American feed samples where glyphosate was detected, MON89788 ranged from 8.7 to 50.7 percent commingling, and DAS-44406, a stacked event carrying 2mepsps, pat, and aad-12 transgenes, reached an extraordinary 41.3 to 71.6 percent. In Brazilian feed samples, MON89788 dominated at 62.6 to 102.6 percent, with the value above 100 percent attributed to inherent measurement uncertainty in event-specific quantitative PCR rather than an impossible true percentage. Meanwhile, the American feed sample in which neither glufosinate nor its metabolite was detected showed low commingling for the pat-containing events, at 0.4 percent for DAS-44406 and 1.1 percent for A5547-127, reinforcing the link between the metabolite and the trait.

The authors interpret these patterns through the lens of regional agricultural practice. In the United States, herbicide use on soybeans has diversified markedly as growers battle glyphosate-resistant weeds. Department of Agriculture surveys show that in 2006 more than 50 million soybean acres were treated exclusively with glyphosate, but by 2012 that area had shrunk by roughly 20 million acres as farmers adopted tank mixes. By 2023, glyphosate isopropylamine remained the most widely used herbicide at 46 percent of planted acres, but 2,4-D choline salt followed at 37 percent, with glufosinate-ammonium at 23 percent. This diversification aligns neatly with the prominence of DAS-44406, whose stacked transgenes confer tolerance to glyphosate, glufosinate, and 2,4-D simultaneously.

Brazil tells a different story. No-tillage systems dominate Brazilian soybean production, and without plowing to control weeds, farmers lean heavily on herbicides; glyphosate was applied to roughly 95 percent of the soybean area by 2021. The insect-protected and glyphosate-tolerant stacked variety MON 87701 x MON 89788, introduced in the 2013/14 season, expanded from 1.2 million hectares to more than 30 million hectares, about 80 percent of national acreage by 2020/21. That near-total adoption explains why MON89788 commingling in Brazilian feed samples reached such extreme levels, while glufosinate-tolerant events remained scarce at 0.2 to 3.2 percent. The researchers note that as glyphosate-resistant weeds spread in Brazil, additional herbicide-tolerance traits may follow the American trajectory, making continued monitoring essential.

The study’s implications extend beyond curiosity. If herbicides or their metabolites appear in a product labeled non-GM, that could signal the presence of GM material and justify verification against labeling regulations, as illustrated by the glufosinate found in the identity-preserved American samples, which the authors attribute to cultivation practices, environmental sources, post-harvest handling, or commingling below the detection range of the genetic assays. Conversely, residue data can cross-check genetic findings, boosting overall reliability. The authors also point toward future work on 2,4-D and dicamba, whose tolerance events, DAS-44406 and MON87708 respectively, metabolize these auxin-mimicking herbicides into detectable signature compounds. Because the sample set was small, the team frames the work as exploratory rather than a quantitative correlation analysis, but the concept is clear: two regulatory silos, pesticide monitoring and GM surveillance, each hold half of a story that only makes full sense when the datasets are combined. Extending this integrated approach to maize and other crops could give food safety authorities a powerful, mutually validating tool for traceability and enforcement in global commodity chains.

Subject of Research: Association between herbicide residues and herbicide-tolerance GM soybean events in imported soybean samples

Article Title: Association between herbicide residues and herbicide tolerance-related genetically modified events in imported soybean samples

Article References: Soga, K., Yoshiba, S., Takabatake, R., Taguchi, T., Tsutsumi, T., Ito, R., Iwasaki, Y., Akiyama, H., & Shibata, N. (2026). Association between herbicide residues and herbicide tolerance-related genetically modified events in imported soybean samples. Journal of Agriculture and Food Research, 31, Article 103321. https://doi.org/10.1016/j.jafr.2026.103321

Image Credits: AI Generated

DOI: 10.1016/j.jafr.2026.103321

Keywords: glyphosate, glufosinate, genetically modified soybeans, herbicide tolerance, real-time PCR, food safety monitoring, maximum residue limits, MON89788, DAS-44406, identity preservation, Brazil soybean exports, United States soybean exports

The technical logic of transgenesis is straightforward but powerful. Where a breeder seeking a target trait must find it within the primary gene pool of a crop, a transgenic approach can source the gene from any organism, including microbes, unrelated plants, or even the crop’s own genome rearranged in new ways. The major traits incorporated into commercial transgenic crops to date fall into four broad categories: herbicide tolerance, insect resistance, tolerance of abiotic stresses such as drought and salinity, and nutritional enhancement. Insect-resistant crops typically deploy genes derived from the soil bacterium Bacillus thuringiensis, whose crystalline toxin proteins, modified for enhanced expression in plant tissues, disrupt the gut of specific larval pests while leaving beneficial insects largely unharmed. Herbicide-tolerant crops carry enzymes insensitive to broad-spectrum herbicides such as glyphosate, allowing farmers to control weeds with simpler spray regimes. The review emphasizes that these are not exotic interventions but extensions of a long tradition of genetic exchange that plant breeders have practised for a century, from the transfer of leaf-rust resistance from Aegilops umbellulata into wheat in the 1950s to the wide hybridization programmes that underpin modern triticale.

The global adoption record is striking. Since the first commercial plantings in 1996, biotech crops have spread to tens of millions of hectares across more than two dozen countries, with soybean, maize, cotton and canola dominating the area. Meta-analyses of agronomic and economic outcomes, including the widely cited work of Klümper and Qaim, indicate that transgenic varieties have generally delivered reduced pesticide use, higher yields and improved farmer profits, with the largest gains accruing to smallholders in developing countries. Economic assessments covering 1996 to 2020 estimate cumulative farm income gains in the tens of billions of dollars and document reductions in pesticide spraying and associated carbon emissions. The review notes that these benefits have not been uniform, and that outcomes depend heavily on the trait, the crop, the pest complex and the stewardship practices that accompany deployment, but the overall pattern of evidence supports the view that the technology, when well managed, has been a net positive for productivity and environmental load.

India’s own experience with Bt cotton is the centerpiece of the domestic evidence base. Approved for cultivation in 2002, Bt cotton expressing the Cry1Ac toxin, and later stacked events, spread rapidly to cover more than ninety percent of the cotton area, transforming India from a cotton importer into one of the world’s largest producers and exporters. Yields rose, insecticide sprays against bollworms fell, and farm incomes improved in the early years of adoption. Yet the review is candid about the cautionary side of the story. Field-evolved resistance in the pink bollworm, Pectinophora gossypiella, was documented in central India within a decade of introduction, and widespread infestations on Bt cotton have since eroded some of the early gains. The authors point to inadequate compliance with refuge requirements, the planting of non-Bt cotton strips designed to slow the evolution of resistant pests, and the persistence of unapproved or diluted seed markets as contributing factors. The lesson, they argue, is not that the technology failed but that stewardship, seed quality control and resistance management are inseparable from any transgenic deployment.

Safety concerns have shadowed transgenic crops from the outset, and the review confronts them directly. Novel gene combinations have raised questions about potential risks to human and animal health, biodiversity and the environment, and these questions have fuelled some of the most contentious episodes in modern science communication. The authors revisit the Séralini affair, in which a 2012 rodent feeding study linking glyphosate-tolerant maize to tumours was widely criticized on statistical and design grounds, retracted, and later republished elsewhere, with regulatory agencies including the European Food Safety Authority concluding that it did not demonstrate harm. They also note the monarch butterfly controversy, in which laboratory findings of Bt pollen toxicity to larvae were subsequently weighed against field evidence and habitat loss as the dominant driver of population declines. More broadly, comprehensive reviews of livestock feeding studies have found no consistent adverse health effects from approved GM feed, and the National Academies of Sciences, Engineering and Medicine concluded in 2016 that genetically engineered crops are as safe as their conventional counterparts when properly regulated. The review stresses that every commercial transgenic crop undergoes rigorous evaluation for agronomic performance, food and feed safety, and compositional equivalence before release.

One of the more provocative threads in the review is the argument that transgenes are not inherently hazardous and that nature itself has been moving genes across species boundaries for millennia. The cultivated sweet potato, a staple food for millions, carries Agrobacterium T-DNA sequences with expressed genes in its genome, the result of ancient horizontal gene transfer, making it in a literal sense a naturally transgenic crop. Widespread horizontal gene transfer between plants and bacteria continues to be documented in modern genomes. The authors argue that increasing public awareness of such facts is critical for building societal confidence, because the perception of transgenesis as an alien and uniquely dangerous intervention rests on a misunderstanding of both the technology and natural biology. Transparent communication, they contend, must become a core component of any deployment strategy rather than an afterthought.

Gene flow and containment receive detailed technical treatment. Pollen-mediated transgene escape from cultivated fields to wild or weedy relatives has been demonstrated in crops such as rice, rapeseed and cotton, and the review surveys the strategies available for containment, including chloroplast transformation, male sterility systems, genetic use restriction technologies and spatial isolation. The risk profile, however, is highly crop-specific. A transgenic trait in a self-pollinating crop with no compatible wild relatives in the region of cultivation poses a very different ecological question than the same trait in an outcrossing species surrounded by interfertile wild populations. This crop-specific logic underpins the review’s central recommendation about where India should focus its transgenic efforts next.

Applying criteria that include the availability of target traits within the primary gene pool, consumption patterns, ecological risks and lessons from past experience, the authors identify transgrafted fruits, sugarcane, forage crops and maize as promising candidates for India. Transgrafting is technically elegant: a transgenic rootstock conferring disease resistance or other traits can be grafted with a non-transgenic scion, and in some systems mobile molecules such as transgene-derived small interfering RNAs travel from rootstock to scion, conferring virus resistance without genetically modifying the harvested fruit. Studies in grapevine, apple, sweet cherry, plum and blueberry have demonstrated the feasibility of the approach, and because the edible product may not carry the transgene, regulatory and consumer barriers could be lower. Sugarcane, propagated vegetatively and not grown from seed in the field, presents minimal gene-flow risk, while forage crops and maize offer clear targets in pest resistance and stress tolerance, with maize already the subject of global transgenic experience that India can draw upon directly.

The regulatory dimension is treated as decisive. India’s case-by-case framework, overseen by the Genetic Engineering Appraisal Committee, has approved only Bt cotton for commercial cultivation, and the long-pending case of genetically modified mustard illustrates how regulatory decisions can stall under public and political pressure. Meanwhile, the government has moved to clarify the status of genome-edited plants, issuing standard operating procedures for regulatory review of SDN-1 and SDN-2 categories of targeted mutagenesis, which do not introduce foreign DNA and are treated more leniently in many jurisdictions. The review argues that strengthening regulatory capacity, ensuring timely and science-based decisions, and addressing public concerns through transparent communication are essential for effective and socially acceptable deployment. It also points to the experience of Bangladesh, where Bt eggplant was commercialized for smallholders, as evidence that South Asian farming systems can benefit from well-managed transgenic introductions beyond cotton.

The overall message of the review is one of disciplined optimism. Transgenic technology is neither a panacea nor a menace; it is a tool whose value depends on choosing the right crops, the right traits and the right stewardship systems, and on building the regulatory and communicative infrastructure that allows evidence rather than fear to guide adoption. For India, with its mounting pressures of population, climate variability, shrinking arable land and degrading water resources, the authors argue that the strategic question is not whether to use transgenic innovation but where and how to deploy it first. Their answer, grounded in global evidence and Indian experience alike, points toward fruit crops protected through transgrafting, sugarcane, forages and maize as the sensible frontier, with Bt cotton’s mixed legacy serving as both inspiration and warning for the road ahead.

Subject of Research: Global transgenic crop innovations and their strategic application to Indian agriculture

Article Title: Advancing Indian Agriculture Through Global Transgenic Innovations

Article References: Dhillon, B., Singh, A., Sohu, V., & Rakshit, S. (2026). Advancing Indian Agriculture Through Global Transgenic Innovations. Indian Journal of Genetics and Plant Breeding, 86(3), 261-278. https://doi.org/10.1007/s44489-026-00030-3

Image Credits: AI Generated

DOI: 10.1007/s44489-026-00030-3

Keywords: transgenic crops, Bt cotton, India, transgrafting, gene flow, biosafety, herbicide tolerance, insect resistance, pink bollworm resistance, maize, sugarcane, genome editing

The study, led by Reisane Teles Santiago of the Federal University of Recôncavo da Bahia and Embrapa Mandioca e Fruticultura, together with colleagues Massaine Bandeira e Souza, Diego Fernando Marmolejo Cortes and Eder Jorge de Oliveira, carried out one of the first genome-wide association studies (GWAS) of herbicide tolerance in cassava. The researchers evaluated 194 genotypes from the Embrapa Cassava and Fruits breeding program, exposing them to three post-emergence herbicides with very different modes of action: mesotrione, which blocks carotenoid biosynthesis; S-metolachlor, which inhibits very-long-chain fatty acid synthesis; and chloransulam-methyl, an inhibitor of acetolactate synthase.

Timing proved to be everything in the experiment. The team scored phytotoxicity symptoms—leaf burn, chlorosis and wilting—at 3, 6, 9, 15 and 30 days after application, on a five-point scale converted to percentage injury values. Segmented regression analyses showed that the window around 9 to 11 days after application captured both the maximum symptom expression and the greatest differentiation among genotypes. That time point, dubbed PhytoX9DAA, became the phenotype of choice for the genetic mapping. Visual scores were converted to percentage injury, then distilled into genotypic best linear unbiased predictors, or BLUPs, using linear mixed models. After deregression, these continuous genetic values served as the input for association testing.

Genotyping was performed at Cornell University using a genotyping-by-sequencing approach, in which DNA is digested with the ApeKI enzyme, barcoded and sequenced on an Illumina platform. After stringent quality control—removing markers with call rates below 80 percent and minor allele frequencies under 5 percent—and imputation with Beagle, the team retained 23,047 single-nucleotide polymorphisms spread across all 18 cassava chromosomes. The panel, dominated by Brazilian landraces, showed healthy diversity: expected and observed heterozygosity were nearly identical at around 0.24, and linkage disequilibrium decayed rapidly, reaching background levels at roughly 4 to 6 megabases.

Association analyses were run with three complementary statistical models—MLM, MLMM and BLINK—each incorporating both a kinship matrix and population structure covariates derived from principal component analysis to guard against spurious associations. The results were strikingly herbicide-specific. For S-metolachlor, a single SNP on chromosome 9, chr9:1858429, emerged consistently in the BLINK model across 2023, 2024 and the combined analysis. For mesotrione, the picture was far richer: 68 significant SNP associations were detected, distributed across chromosomes 1, 4, 5, 7, 11, 14, 15 and 18, with the strongest signals clustering on chromosome 5, where four adjacent markers hinted at a haplotype block tied to tolerance. Notably, no significant associations surfaced for chloransulam-methyl, a silence the authors attribute cautiously to a possibly highly polygenic architecture, limited statistical power, or the relatively modest marker density of the GBS platform.

Mining the genomic neighborhoods of the significant markers within a 240-kilobase window, the researchers cataloged 59 candidate genes whose annotations read like a molecular toolkit for surviving chemical stress. On chromosome 7, genes annotated with antiporter activity and xenobiotic transmembrane transporter activity evoke the ABC and MATE transporter families, well-known agents of herbicide sequestration and efflux in other plants. On chromosome 1, candidates linked to RNA binding and RNA methyltransferase activity suggest post-transcriptional regulation at play, while chromosome 15 genes carry annotations for transcription factors and transmembrane transport. Key standouts include Manes.02G151900 and Manes.02G152700 on chromosome 2, tied to channel activity and signal peptide processing; Manes.09G060900 on chromosome 9, annotated with protein kinase and ATP-binding functions; and Manes.15G083800 and Manes.15G084000 on chromosome 15, linked to S-adenosylmethionine-dependent methyltransferase activity and phosphorylation.

The authors are careful to stress that these functional interpretations rest on annotation and comparative evidence from other species rather than direct experimental validation in cassava. Still, the emerging picture fits neatly with established mechanisms of metabolic herbicide resistance documented in crops and weeds alike: cytochrome P450-mediated oxidation, glutathione S-transferase conjugation, and vacuolar sequestration via ABC transporters. Comparable GWAS findings in rice, soybean, faba bean and wheat have similarly implicated transporters, protein kinases and detoxification enzymes in herbicide responses, suggesting that cassava may share evolutionarily conserved pathways for coping with xenobiotic stress.

The study also confirmed that substantial heritable variation for herbicide tolerance exists within the cassava gene pool. Variance component analysis showed a highly significant genotypic effect for phytotoxicity at 9 days after application for all three herbicides, meaning breeders have real material to select from. A significant genotype-by-year interaction was also detected across compounds, a reminder that temperature, humidity and growing conditions shape how herbicide injury unfolds in the field. Genomic inflation factors close to 1.0 for the BLINK and MLMM models, together with well-behaved quantile-quantile plots, indicate the association results are statistically sound.

For a crop whose expansion is increasingly squeezed by the rising cost of hand weeding, the practical implications are considerable. The chromosome 9 locus for S-metolachlor tolerance and the robust mesotrione signals on chromosomes 4 and 5 could, after independent validation and functional characterization, feed directly into marker-assisted selection and haplotype-based breeding. Given the polygenic nature of the trait, the authors also point to genomic selection as a complementary route, with GWAS-derived markers potentially boosting prediction accuracy when integrated into training populations. For smallholder farmers in Brazil, Nigeria and beyond, tolerant varieties could translate into cheaper, more reliable weed control and more stable yields.

Scientifically, the message is equally clear: herbicide tolerance in cassava is a quantitative, polygenic trait governed by many small-effect loci rather than a single master switch. The integration of membrane transport, cellular signaling and metabolic regulation highlighted by the candidate genes underscores the physiological resilience that has made cassava such a successful tropical staple. What this study delivers is a genomic map—a first, detailed chart of where that resilience resides in the cassava genome. Fine mapping, gene editing and validation experiments will now be needed to convert candidate loci into tools, but the first genomic dissection of herbicide tolerance in this vital crop has firmly been delivered, opening a path toward cassava varieties bred as much for chemical resilience as for the drought tolerance and low-input hardiness for which the species is already famous.

Subject of Research: Genome-wide association mapping of herbicide tolerance loci in cassava (Manihot esculenta)

Article Title: Pinpointing genomic regions conferring herbicide tolerance in cassava via genome-wide association mapping

Article References: Santiago, R. T., Souza, M. B. E., Cortes, D. F. M., & de Oliveira, E. J. (2026). Pinpointing genomic regions conferring herbicide tolerance in cassava via genome-wide association mapping. Plant Molecular Biology, 116(5), Article 95. https://doi.org/10.1007/s11103-026-01761-3

Image Credits: AI Generated

DOI: 10.1007/s11103-026-01761-3

Keywords: cassava, GWAS, herbicide tolerance, Manihot esculenta, SNP markers, mesotrione, S-metolachlor, candidate genes, marker-assisted selection, plant breeding, genomic selection, detoxification pathways