Assessing the hybridization risks between modern rye-grass cultivars and weed forms in the UK

1. Introduction

The Agriculture and Horticulture Development Board (AHDB) is a non-departmental Government body, funded by levy income from farmers, growers and others in the supply chain, and managed as an independent organisation (independent of both commercial industry and of Government). The role of the AHDB is to help improve the efficiency and competitiveness of various agriculture sectors within the UK. Our purpose is to help our farmers, growers and industry to succeed in a rapidly changing world.

As AHDB is funded in this manner, value for money is paramount, we welcome suppliers who can offer innovative and cost-efficient solutions to meet our needs, whilst also offering superlative service that will enable us to create a world-class food and farming industry. Solutions should look to help us not only reduce costs but increase business flexibility, lift productivity, bring people together to collaborate, innovate and drive change throughout. Further information about AHDB can be found here: https://ahdb.org.uk/

2. Background

Rye-grasses (Lolium), Italian rye-grass (Lolium multiflorum) in particular, are becoming an increasing concern for many growers due to the associated issues around herbicide resistance and the move to more ‘regenerative’ farming practices, which are considered high risk for these weed species. Herbicide resistance in rye-grass was first identified in the UK in 1990 and has since become widespread. There are instances of both non-target site resistance, which is common, and target site resistance to several important classes of herbicides which have led to increasing control issues and problematic hotspots across the country. In January 2025 the first case of glyphosate resistance in the UK was reported from an Italian rye-grass sample in Kent.Since then, further samples of Italian rye-grass have been tested an more have been confirmed as being resistant or having reduced sensitivity (WRAG updates 05/02/2025, 21/08/2025).

Lolium species have the potential to outcross and hybridise with one another. Both perennial and Italian rye-grass, and their hybrids, are sold as part of forage and margin mixtures to UK farmers. The AHDB Recommended Lists for Grass and Clover has a number of perennial and Italian rye-grass cultivars which are considered to be separate to the weed forms that are often found in arable rotations. There is uncertainty about whether rye-grass species found as weeds in the rotation have originated from varieties used for forage and in margin mixtures e.g. rye-grass weeds have been found on farms that don't have a history of using rye-grass for forage or in margins. Though modern breeding has refined cultivated rye-grass species, their ability to hybridise poses a potential threat as resistance to herbicides could potentially be passed between populations and stronger forms of resistance may appear, making rye-grass more difficult and costly to control. However, we currently lack the evidence to support this assumption. Understanding how, and at what level, resistance is passed between populations of cultivated and crop weed forms of rye-grass will help farmers and advisors inform farm management decisions, and support grass breeding programmes in reducing any potentially resistant material.

3. Related information

Weed Resistance Action Group - https://ahdb.org.uk/knowledge-library/the-weed-resistance-action-group-wrag

AHDB Blog Article - https://ahdb.org.uk/news/next-steps-for-managing-glyphosate-resistance-in-grass-weeds

PR631 - https://ahdb.org.uk/managing-the-resistance-risk-to-retain-long-term-effectiveness-of-glyphosate-for-grass-weed-control-in-uk-crop-rotations

Italian rye-grass biology and management - https://ahdb.org.uk/knowledge-library/distribution-biology-and-management-of-italian-rye-grass-in-the-uk

Perennial rye-grass biology and management - https://ahdb.org.uk/knowledge-library/distribution-and-biology-of-perennial-rye-grass-in-the-uk

4. Purpose of the tender

Suppliers are invited to submit proposals for this 8-month study. The aim of the work is to determine the genetic relationship between varieties currently grown for sale as forage or margin mixtures and weed forms on farm in order to assess the risk of hybridisation. Understanding the relationship between these rye-grasses will help to determine the risk of hybridisation, and therefore any potential resistance risks. Outcomes of the project will help to inform management decisions, enabling growers to reduce the risk of resistance in managed rye-grass and wild rye-grass populations. Outcomes will also help to inform varietal breeding programmes by helping to eliminate material that poses a potential resistance risk.

5. Tender Objectives

This research will deliver the following.

1. Genetic screening of commercial rye-grass varieties included on the current AHDB Recommended Lists for Grasses and Clovers.
2. Genetic screening of weed rye-grass samples, to be representative of the UK and include samples from ‘high risk’ farms, e.g., those farms considered to be conducting practices which are not advised in the control of Italian rye-grass or perennial rye-grass such as re-generative farming practices.
3. Analysis of genetic data to determine the relationship between rye-grass cultivars and rye-grass weed samples.
4. Findings of the project to be summarised in a report by the end of the project. The report should include:
   
   1. A full description of the methodology, analyses and results.
   2. An assessment of the risk of hybridisation is between cultivated and wild forms of rye-grass.
   3. A section on suggested guidance and future research.
   4. Further information and templates for these reports can be found at AHDB Cereals & Oilseeds research report templates
5. Appropriate knowledge exchange plan (to take place throughout the duration of the project) including dissemination of findings at AHDB events, e.g., AHDB Agronomy Conference 2026, to be included within the budget allocated.
6. Liaise with the Weed Resistance Action Group (WRAG) and BCPC Weeds Working Group to update guidance where relevant.
7. Liaise with breeding companies to communicate outcomes where relevant.

6. Scope and Approach

Proposals should include a detailed description of the planned works including:

• Clear evidence of how the approach is addressing the objectives and deliverables outlined in section 5.
• Justification for the suggested approach including any relevant references to other work using the same or similar methodology.
• The sources of the weed seed samples to be used, including the number and geographical spread of samples to be tested.
• The sources of rye-grass varietal seed to be used. Please include the number and range of species/varieties that will be tested within the quoted price.
• Details of how the project will be managed, including a staff contingency plan in the case of absence.
• A detailed knowledge exchange plan for the project including social media, events and published channels.
• Breakdown of costings within the quoted price. Please include details of the co-funding to be provided in addition to the requested funds from AHDB (see Section 7).

A final project report will be required along with participation in our annual project monitoring exercise. Further information and templates for these reports can be found at AHDB Cereals & Oilseeds research report templates.

7. Project Duration, Budget, and Collaboration

AHDB has set aside a maximum total budget of £41,000, inclusive of vat (£35,650 exclusive of VAT) over 8 months. The earliest date of commencement for work funded as a result of this call will be 30/03/2026.

Suppliers must detail at least two confirmed sources of co-funding within the submitted proposal. The co-funding can be in-kind or cash contributions relevant to the project.

Research Partnership Approach

Joint proposals from two or more contractors are acceptable and encouraged where there is added value. AHDB may, if it is deemed desirable, request applicants to form a consortium to work together. There should be one organisation designated as the lead organisation for the Research Partnership which is responsible for project management and delivery. The group size should be manageable. Prospective partnerships can comprise both research institutes and industrial partners, be multi-disciplinary, and draw on a range of research experience for a number of crops. Therefore, the group does not necessarily need to have a history of working together previously.

8. Structure/format of submission

Applicants should complete the AHDB Research and KE Application Form - Full Proposal Small, referring to the guidance notes to aid completion. Alternatively, applicants can submit a proposal in a format of their choice.  Completed application forms should be submitted to research@ahdb.org.uk no later than noon on the 27/02/2026.

On submitting a proposal, please ensure you have read and accepted our terms and conditions, these are available on our website here under the “Standard agreements” heading. Any organisation receiving funding from AHDB shall comply with the terms and conditions specified in the Research Funding Agreement. AHDB will not be held responsible for any expenses or losses incurred by applicants in the preparation of an application(s).

AHDB reserves the right to not proceed with any application or, if appropriate, to request applicants to form a consortium to work together to deliver a programme of activities.

An evaluation panel will assess submissions in line with the scoring criteria and weightings in section 9 to decide the best outcome for this research project.

9. Evaluation and award of contract

All submitted proposals will be reviewed by relevant representatives within AHDB, and the respective Research and Knowledge Exchange Committees. If required, external peer reviewers may be sought. The selection will be an open and fair competition according to AHDB’s procurement policy, which complies with EU state aid rules.

Evaluation of proposals will be on evidence provided against the following criteria:

10. Proposal submissions

Applications must be received by noon 27 Feburary 2026. Submissions to be made electronically to research@ahdb.org.uk quoting the reference P2512385: Assessing the hybridization risks between modern rye-grass cultivars and weed forms in the UK. 

Submissions will remain unopened until after the closing date and time has passed

11. Timetable

Please note these timescales are approximate and may change.

A project initiation meeting will be held between the successful bidder and the project funders at the commencement of the contract.  Additional meetings will be held as required for progress updates.

12. Terms/conditions of participation

AHDB terms and conditions shall apply to any contract awarded as a result of this request for invitation to tender.

If you have specific questions relating to this call, please email research@ahdb.org.uk. All Questions & Answers will be  anonymised and published.

As part of the open tender process, AHDB cannot discuss specific programme details prior to proposal submission.

If you have any questions relating to this tender, please contact