Research and analysis

ACRE guidance on producing precision bred plants

Published 13 November 2025

Applies to England

This document relates to the Genetic Technology (Precision Breeding) Act 2023 and the Genetic Technology (Precision Breeding) Regulations 2025.

A ‘precision bred’ plant contains genetic features produced using modern biotechnology (such as genome editing) that could also have been produced by traditional processes. 

This document outlines: 

• the criteria for a precision bred plant 
• the scientific basis for these criteria 
• genetic features produced by the application of modern biotechnology and whether they would result in a precision bred plant 

The document will be updated to keep pace with scientific developments and user experience.  

If you plan to release or market a precision bred plant (or food and feed derived from it), you may need to confirm you have read this document. You should follow the guidance on releasing and marketing precision bred plants.

1. Scientific background 

A large body of scientific evidence demonstrates that genetic material naturally exists in variant forms, even between or within individuals of the same species.  

Naturally occurring genetic variation such as this is exploited by breeders to produce improved plant varieties. They use a range of techniques and interventions to generate and capture this genetic variation. Precision bred plants contain these types of genetic changes. 

The scientific evidence includes the following publications:

• ACRE advice on Defra’s consultation on the regulation of genetic technologies
• ACRE’s report: Genetically modified organisms: the case for new regulations
• Benoit, M, Jenike, KM, Satterlee, JW and others (2025). ‘Solanum pan-genetics reveals paralogues as contingencies in crop engineering’, Nature, volume 640, pages 135 to 145
• Chen, L, Luo, J, Jin, M and others (2022). ‘Genome sequencing reveals evidence of adaptive variation in the genus Zea’. Nature Genetics, volume 54, pages 1,736 to 1,745
• Cochetel, N, Minio, A, Guarracino, A and others (2023). ‘A super-pangenome of the North American wild grape species’. Genome Biology, volume 24, article 290
• Della Coletta, R, Qiu, Y, Ou, S and others (2021). ‘How the pan-genome is changing crop genomics and improvement’. Genome Biology, volume 22, article 3
• Healey, AL, Garsmeur, O, Lovell, JT and others (2024). ‘The complex polyploid genome architecture of sugarcane’. Nature, volume 628, pages 804 to 810
• Li, N, He, Q, Wang, J and others (2023). ‘Super-pangenome analyses highlight genomic diversity and structural variation across wild and cultivated tomato species’. Nature Genetics, volume 55, pages 852 to 860
• Li, X, Wang, Y, Cai, C and others (2024). ‘Large-scale gene expression alterations introduced by structural variation drive morphotype diversification in Brassica oleracea’. Nature Genetics, volume 56, pages 517 to 529
• Niu, J, Ma, S, Zheng, S and others (2023). ‘Whole-genome sequencing of diverse wheat accessions uncovers genetic changes during modern breeding in China and the United States’. The Plant Cell, volume 35, issue 12, pages 4,199 to 4,216
• Sun, H, Jiao, WB, Krause, K and others (2022). ‘Chromosome-scale and haplotype-resolved genome assembly of a tetraploid potato cultivar’. Nature Genetics, volume 54, pages 342 to 348
• Wang, L, Zhang, Z, Han, P and others (2023). ‘Association analysis of agronomic traits and construction of genetic networks by resequencing of 306 sugar beet (Beta vulgaris L.) lines’. Scientific Reports, volume 13, article 15,422

2. Criteria

For a plant to be considered ‘precision bred’, it must meet criteria outlined in the act.

The act defines an organism as ‘precision bred’ if:

• it contains any stable genomic feature produced using modern biotechnology
• the feature could have resulted from traditional processes

Alterations can be introduced in the DNA sequence and the epigenome, including both nuclear and non-nuclear genomes.

There is no specific limit on the number or size of genomic alterations that can be made within a single precision bred plant, as long as the alterations could have arisen through traditional processes.

 Genetic stability

The genetic changes introduced by modern biotechnology must be stable. This means developers will need to demonstrate they can be inherited following either sexual or asexual reproduction. 

Natural mutations can occur in a precision bred plant following confirmation of precision bred status. Developers are not expected to monitor or prevent these.

Traditional processes

The act defines a list of traditional processes. These cover the range of genetic changes that could feasibly occur in plants over the course of its lifetime or in a conventional breeding programme.

Naturally occurring changes include but are not limited to:

• point mutations, which could arise from mistakes in DNA polymerase activity
• chromosomal translocations, which could arise from mis-segregation of chromosomes during replication

Genetic changes that would not result in a precision bred plant

A plant is not precision bred if it contains transgenic material, including editing cassettes, selectable markers and vector genes.

Transgenic intermediates produced to enable the editing process can be used if all transgenic sequences are removed prior to release or marketing. Transgenic sequences are those whose presence in the plant could not have arisen through traditional processes.

Factors not affecting precision bred status

 The following factors do not impact the determination of a plant’s precision bred status:

• copy number variation (CNV)
• epigenetic status
• location of genetic changes

CNV is known to have significant natural variation within populations and does not directly correlate to protein expression and trait development.

Similarly, epigenetic status varies across the lifetime of plants.

The genomic location of genetic changes does not affect precision bred status because spontaneous mutations occur throughout genomes over time. Similarly induced mutations, such as those arising from traditional processes, also occur randomly throughout genomes.

3. Genome editing mechanisms: Site-directed nucleases (SDNs)

Precision bred plants may be developed using site-directed nucleases (SDNs). These genome editing systems (such as CRISPR-Cas9) can create DNA strand breaks at specific locations within a genome.

3.1 SDN1-type changes to genetic material

In SDN1, the strand break is repaired by endogenous DNA mechanisms, usually non-homologous end joining (NHEJ).

NHEJ is an error-prone repair mechanism that often results in small insertions or deletions (indels) to the DNA sequence. These indels may alter the function of a protein or affect the action of non-protein coding regulatory sites.

Single or double strand breaks followed by repair through endogenous repair mechanisms like NHEJ is a process that naturally produces spontaneous mutations during the lifetime of a plant.

This aligns with the traditional processes set out in the act. As a result, plants developed using SDN1 would likely be considered precision bred organisms.

Multiplex editing  

Developers may also use SDN1 to target multiple sites at once, to generate lesions at 2 or more spatially separated locations within a chromosome.

In this way, larger stretches of DNA can be deleted or inverted, potentially removing one or more whole genes or non-coding regions. This approach can result in significant rearrangements, deletions or duplications of translocations of genetic material.

These are events that also occur and can be selected for when using traditional breeding techniques, where they may be mediated by agents such as transposons or other mutagens.

Examples of gene-edited plants created using SDN1-type changes to genetic material

The following publications generally describe SDN1-type genetic changes to crops.

• Chen, Y, and others (2020). ‘High‐oleic acid content, nontransgenic allotetraploid cotton (Gossypium hirsutum L.) generated by knockout of GhFAD2 genes with CRISPR/Cas9 system’. Plant Biotechnology Journal: volume 19, issue 3, pages 424 to 426
• Do, PT and others (2019). ‘Demonstration of highly efficient dual gRNA CRISPR/Cas9 editing of the homeologous GmFAD2–1A and GmFAD2–1B genes to yield a high oleic, low linoleic and α-linolenic acid phenotype in soybean’. BMC Plant Biology: volume 19, issue 1, article 311
• Nonaka, S and others (2017). ‘Efficient increase of ɣ-aminobutyric acid (GABA) content in tomato fruits by targeted mutagenesis’. Scientific Reports (online): volume 7, issue 1, page 7,057
• Raffan, S and others (2021). ‘Wheat with greatly reduced accumulation of free asparagine in the grain, produced by CRISPR/Cas9 editing of asparagine synthetase gene TaASN2’. Plant Biotechnology Journal: volume 19, issue 8, pages1,602 to 1,613

Examples of gene-edited plants created using SDN1 to generate larger indels

The following publications generally describe gene-edited plants where SDN1 has been used to generate larger indels.

• Brooks, C and others (2014). ‘Efficient gene editing in tomato in the first generation using the clustered regularly interspaced short palindromic repeats/CRISPR-associated9 system’. Plant Physiology (online): volume 166, issue 3, pages 1,292 to 1,297
• Chandrasekaran, J, and others (2016). ‘Development of broad virus resistance in non-transgenic cucumber using CRISPR/Cas9 technology’. Molecular Plant Pathology: volume 17, issue 7, pages 1,140 to 1,153
• Li, S, and others (2022). ‘Genome-edited powdery mildew resistance in wheat without growth penalties’. Nature (online): volume 602, issue 7,897, pages 455 to 460
• Zhao, Y, and others (2016). ‘An alternative strategy for targeted gene replacement in plants using a dual-sgRNA/Cas9 design’. Scientific Reports: volume 6, issue 1, article 23,890
• Zhou, H, and others (2014). ‘Large chromosomal deletions and heritable small genetic changes induced by CRISPR/Cas9 in rice’. Nucleic Acids Research: volume 42, issue 17, pages 10,903 to 10,914

The techniques described in the selected publications above may not produce precision bred plants. To be confirmed as a precision bred organism, there can be no transgenic elements present, including gene-editing cassettes, selectable markers and vector genes.

3.2 SDN2 and SDN3

Precision bred plants can be developed using other cellular mechanisms, such as homology-directed repair (HDR), to change specific sequences within the genome of a plant.  

SDN2 and SDN3 also create strand breaks at a predetermined location. However, inclusion of a DNA template allows exploitation of HDR, which directs the DNA repair machinery to generate the precise sequence change that is required.

SDN2 results in smaller sequence changes or corrections. SDN3 results in the targeted insertion of longer stretches of genetic material, such as a whole gene or several contiguous genes.

SDN2 edits

SDN2 directly exploits existing cellular mechanisms that may be used when repairing spontaneous mutations that occur in a plant genome. It therefore aligns with the traditional processes set out in the act.

As a result, plants developed using SDN2 could be considered precision bred organisms as long as:

• any functional transgenes (such as selectable markers and vectors introduced during the development of the plant) have been removed and are no longer present
• the genetic changes could have resulted from traditional processes

SDN3 edits

SDN3 techniques could produce outcomes that arise through ‘traditional processes’ set out in the act. This applies if the genetic material inserted could have been crossed from within the existing gene pool of the plant.

This would mean the plant could be considered as precision bred. 

Examples of gene-edited plants created using SDN2 and SDN3

These publications generally describe examples where SDN2 and SDN3 have been used to create gene-edited plants, via HDR.

• Li, J, and others (2018). ‘Efficient allelic replacement in rice by gene editing: A case study of the NRT1.1B gene’. Journal of Integrative Plant Biology (online): volume 60, issue 7, pages 536 to 540
• Shi, J and others (2017). ‘ARGOS8 variants generated by CRISPR-Cas9 improve maize grain yield under field drought stress conditions’. Plant Biotechnology Journal (online): volume 15, issue 2, pages 207 to 216

The techniques described in the selected publications above may not produce precision bred plants. To be confirmed as a precision bred organism, there can be no transgenic elements present, including gene-editing cassettes, selectable markers and vector genes.

3.3 Prime and base editing 

Using an adaptation of the genome editing techniques described above, developers can precisely direct which specific nucleotide or nucleotides are changed within a genome without generating a double strand DNA break.

To achieve this, an SDN such as CRISPR-Cas9 is modified so that it nicks one of the DNA strands at a predetermined location. An enzyme linked to the SDN converts the incumbent nucleotide to an alternate one.

As with SDN1, prime and base editing make the same type of genetic changes that occur naturally. These are already exploited by breeders using traditional processes when selecting for varieties that have specific single nucleotide polymorphisms (SNPs).

There is no upper threshold on the number of SNPs that can be introduced, provided they could have accumulated in the plant through traditional processes.

4. Recombinant DNA techniques

4.1 Transgenic changes to genetic material

There are clear examples of genetic changes that do not result in precision bred organisms. Usually referred to as ‘transgenic’, they involve:

1. Manipulation of a DNA molecule from a non-crossable species outside of the cell (in vitro).
2. Inserting the DNA molecule into the genome using recombinant DNA technology.

The resulting plant is not a precision bred organism because its genetic composition does not fall within the variation that could occur:

• naturally within that species (or a related species)
• through traditional techniques and selection

An example of a transgenic changes to genetic material relevant to many gene-editing approaches is the insertion of the bacterial CRISPR-Cas9 gene into a plant genome. The genetic composition of the resulting plant is very unlikely to have occurred naturally or through traditional techniques and selection. This means the plant would not be a precision bred organism. 

If this gene was later removed (for example, through segregation), that plant could then be classed as precision bred if it both:

• contains no other transgenes, such as selectable markers or other vector derived genes
• meets the other required criteria outlined in this document

This example shows it is important to consider if the inserted DNA molecule originated from a species that is sexually compatible (or crossable) with the recipient species. If it did not originate from a sexually compatible (or crossable) species, the plant is not precision bred. 

Synthetic elements

Another approach that results in a transgenic organism is where an inserted DNA molecule encodes a synthetically designed peptide or protein not known to exist in nature. This would not be possible through the use of traditional processes and therefore any plant containing these would not be a precision bred organism. 

The following publications describe examples where novel synthetic elements have been used to develop sustainable resistance to pests and diseases in crops:

• Green J and others (2012). ‘Transgenic potatoes for potato cyst nematode control can replace pesticide use without impact on soil quality’. PLoS ONE: volume 7, issue 2, article e30973
• Kanniah Rajasekaran and others (2018). ‘Control of Aspergillus flavus growth and aflatoxin production in transgenic maize kernels expressing a tachyplesin-derived synthetic peptide, AGM182’. Plant Science: volume 270, pages 150 to 156
• Pradeep K Papolu and others (2020). ‘The production of a synthetic chemodisruptive peptide in planta precludes Meloidogyne incognita multiplication in Solanum melongena’. Physiological and Molecular Plant Pathology: volume 112, article 101,542

In most cases, it will be clear that the plant produced is not a precision bred organism on the basis of the detailed experimental information recorded during the development and molecular analysis of the plant.

Additional examples of transgenesis

There are other clear examples of transgenesis. For example, where a plant contains a gene from an animal or a fungus.

The following publications describe further examples of transgenesis in gene-edited plants:

• Chen, Z, Liu, Y, Yin, Y and others (2019). ‘Expression of AtGA2ox1 enhances drought tolerance in maize’. Plant Growth Regulation: volume 89, pages 203 to 215
• Fernanda Gabriela González and others. ‘Field-grown transgenic wheat expressing the sunflower gene HaHB4 significantly out yields the wild type’. Journal of Experimental Botany: volume 70, issue 5, 15 February 2019, pages 1,669 to 1,681 

4.2 Cisgenic changes to genetic material

Cisgenesis involves the introduction of genetic material from a sexually compatible donor species into a recipient. Unlike SDN3, older style cisgenic techniques require construction of a recombinant vector outside of the host organism. This is then integrated into the genome at a random location.

Cisgenes generally include all the naturally occurring genetic elements observed in the donor species, including introns and the native promoters and terminators. They also generally require short left and right borders, such as T-DNA borders, to enable insertion.

Plants created using cisgenic techniques are considered precision bred organisms if the genetic material inserted could have been introduced into the plant by traditional processes. This applies regardless of whether the inserted sequence was cloned from a donor plant or synthesised using knowledge of the contiguous sequences involved.

Border sequences

The presence of left and right border sequences, such as T-DNAs, does not preclude a plant from being considered precision bred.

Technically these small sequence additions would be classed as exogenous. However, there is a strong scientific rationale for suggesting that their presence may be discounted. This is because exogenous sequences are naturally present in the genomes of modern cultivated varieties. Some of which are derived from widely divergent species, including from other phylogenetic Kingdoms.

This is shown in the following paper: 

Jianchao Ma, Shuanghua Wang, Xiaojing Zhu, Guiling Sun, Guanxiao Chang, Linhong Li, Xiangyang Hu, Shouzhou Zhang, Yun Zhou, Chun-Peng Song, Jinling Huang (2022). ‘Major episodes of horizontal gene transfer drove the evolution of land plants’. Molecular Plant, volume 15, issue 5, pages 857 to 871

Multiple cisgenic changes

A precision bred plant may contain multiple cisgenes at a single locus or single cisgenes at multiple loci.

There is no specific limit on the number of cisgenes that can be introduced at once, provided this is consistent with the genetic variation that could occur:

• naturally within sexually compatible relatives
• through traditional processes and selection

4.3 Intragenic changes to genetic material

The main difference between intragenesis and cisgenesis is that intragenesis generally involves either:

• exon or intron swapping or splicing
• creating a recombinant DNA molecule with the coding region of one gene associated with the non-coding regulatory domains of one, or several, different genes

Importantly, by definition, in intragenesis all these genetic elements are derived from species that are sexually compatible with one another.

Intragenesis involves highly specific shuffling of intragenic regions and their regulatory domains to create novel splice variants with regulatory domains from unrelated genes. The traditional processes outlined in the act are unlikely to result in this. As a result, plants created through intragenesis are unlikely to meet the criteria for a precision bred organism as described in the act.

However, demonstration of a strong rationale that the genetic changes could have arisen through traditional processes will be considered.

Examples may include circumstances where the developer has produced recombinant DNA representing the complete coding region of a gene, alongside regulatory domains that feasibly could come to control the inserted gene (for example, through translocation).

5. Summary

Plants containing changes resulting from cisgenesis or SDNs are likely to be considered precision bred organisms, so long as:

• functional transgenes, such as selectable markers and vectors, have been removed (for example, by segregation)
• genetic changes introduced could have resulted from traditional processes and selection

Some possible exemptions are:

• where numerous genomic alterations have been made simultaneously – developers will need to consider if the amount of introduced genetic variation could have resulted from traditional processes and provide strong scientific rationale that this would be possible
• genomic changes that result in sequences or traits that could not reasonably be expected to arise through traditional processes

Plants containing the type of genetic changes resulting from intragenesis are unlikely to be considered precision bred unless a strong rationale for this is provided.

Transgenic plants contain genetic material from species that could not have been introduced through traditional processes and are therefore not precision bred organisms. 

Get help

If you are uncertain whether a specific plant generated using a genetic technology such as gene editing would be considered a precision bred organism, contact Defra:

Email: pb-regulation@defra.gov.uk