Novel strategies for genetic improvement of disease resistance in perennial ryegrass

Lead Research Organisation: Aberystwyth University
Department Name: IBERS

Abstract

Perennial ryegrass (PRG) provides the majority of forage for livestock in the UK. Drechslera andersonii or net blotch is a serious fungal disease of PRG, and the UK is at high or medium risk. Yield effects can be over 1t DM per hectare in the first cut (British Society of Plant Breeders - Recommended List). Few current diploid varieties have good resistance, and the UK bred high sugar grass (HSG) varieties show poor resistance. Fungicide use is not a viable option. Reduction in the use of HSG varieties will lead to decreasing sales and increase in imported varieties with higher resistance, but without the high sugar content, which improves ruminant nutrition efficiency. The project brings together the only UK owned forage grass and legume seed production and wholesale company (Germinal Holdings Ltd), and the major forage plant breeding and genetics research organisation within the UK (IBERS, Aberystwyth University) in a consortium that has the skills and commercial experience to deliver new net blotch resistant PRG varieties with HSG characteristics. IBERS, Aberystwyth University will breed net blotch resistant HSG varieties using a novel backcross strategy aided by genomic selection. This will increase the speed with which disease resistant hybrids recover previous values of agronomic and HSG traits. This has not been done before in a ryegrass breeding programme. New net blotch resistant HSG ryegrass varieties will help GHL maintain and increase market share in the UK and abroad. We have identified ecotypes with high net blotch resistance. They will initially be crossed with AberWolf, a high performing HSG varieties with low net blotch resistance. The F1 progeny will be assessed phenotypically for disease resistance, and genotyped with a 4000 molecular marker SNP chip. This allows us to identify quantitative trait loci (QTLs) for net blotch resistance. Secondly, prediction models have been developed to derive genomic estimated breeding values for agronomic and forage quality traits. This will enable us to select the best candidates for disease resistance as well as HSG traits. A polycross of the F1 plants will be performed to guarantee segregation of the disease resistance traits. By year 5 three further rounds of backcrossing with the recurrent HSG parent will have been completed. Seed will be set aside from year 3 for small scale field trials in Devon for the remaining two years. These field trials will also include a wide range of susceptible and resistant material with high or low water soluble carbohydrate (WSC) content for comparison and as controls. These rigorous trials will ensure that by the end of the project, we will have populations with much higher net blotch resistance in addition to the beneficial properties of AberHSG varieties in terms of yield, WSC and digestibility. A range of activities will be undertaken to publicise this work, and thus facilitate fast on-farm uptake of these new varieties. This includes communication with seed distributors, advisors and farmers. The technology will be demonstrated at various livestock shows, including demonstration plots, where possible. GHL will also produce easy to follow management guidelines for farmers.

Technical Summary

Perennial ryegrass (PRG) provides the majority of forage for livestock in the UK, and delivers commercial returns to Germinal Holdings (GHL) through seed sales worth £8250K. Drechslera andersonii or net blotch is a serious fungal disease of PRG, and the UK is at high or medium risk. Resulting yield reductions can be very significant. Few current diploid varieties have good resistance, and the UK bred high sugar grass (HSG) varieties show poor resistance. Fungicide use is not a viable option. Reduction in the use of HSG varieties will lead to decreasing sales and increased imported varieties with higher resistance, but without the high sugar content, which improves ruminant nutrition efficiency (Lee et al. 2001, Anim. Res. 50, 441-449). A 20% reduction in HSG seed sales represents 400 t (£1000K), and has serious commercial implications for GHL. IBERS, Aberystwyth University will breed net blotch resistant HSG varieties using a novel backcross strategy aided by genomic selection. This will increase the speed with which disease resistant hybrids recover previous values of agronomic and HSG traits. New net blotch resistant HSG ryegrass varieties will maintain and increase GHL sales.

Planned Impact

The livestock farmers will benefit from the new net blotch resistant HSG varieties by providing a high yielding high quality forage without the yield reductions resulting from net blotch attacks. The HSG varieties have also been shown to improve the efficiency of utilisation of plant protein by the ruminant animals.

The novel genomic selection-aided backcross approach described in the project will benefit the plant breeders and the wider scientific community by providing sufficient phenotypic and genotypic data to enable accurate mapping of the quantitative trait loci for net blotch pathogen resistance, and thus facilitate the elucidation of its genetic basis. Depending upon its genetic architecture it may also provide molecular markers with large effect, which could be used in future marker assisted selection programmes. The use of genetic selection to help providing faster genetic gain from backcross breeding will also benefit the scientific community by providing proof of principle of this approach, and a potential blueprint for applying this technology in other forage crop breeding programmes.

The development of new perennial ryegrass varieties in the UK will not only enable Germinal Holdings Ltd (GHL), who is the commercial partner in this project, to maintain or increase its share of the UK ryegrass seed market, but it will also benefit the UK balance of payments. Without the new UK developed varieties, a 20% (1000 t) increase in ryegrass seed imports, would represent a negative impact worth £2.5M for the UK. Conversely, a 5% increase in market share for GHL, brought about by the development of resistant Aber high sugar grasses (HSG) varieties, would mean an extra 500 t of seed worth about £500K/annum for GHL.

There is also a potentially positive impact on the environment from increased use of HSG varieties. Studies have shown that lambs fed on HSG produce 20% less methane than lambs fed on a control variety of forage grass, possibly due to their high eney content. In three zero-grazing trials involving early, mid and late lactation animals the amount of feed nitrogen lost in the urine was reduced by up to 24% from animals fed the HSG variety.

Publications

10 25 50
 
Description The main objective is to generate perennial ryegrass high sugar grass breeding populations with improved resistance to leaf spot disease, an increasingly important fungal pathogen. This is done through a backcrossing programme from ecotypes with high resistance into IBERS high sugar grass elite breeding populations. So far we have reached the F2 generation, and the crossing has proceeded according to plan. Genotypic data are now available to assist in the selection of best candidates for further backcrossing. Further polycrossing of most resistant families is in progress in 2019. This will be accompanied by genotype data to assist in the selection process.
Exploitation Route Leaf spot resistant ryegrass germplasm will be used in variety development by Germinal.
Sectors Agriculture, Food and Drink

 
Description In training days at IBERS for agronomists and farmers
First Year Of Impact 2017
Sector Agriculture, Food and Drink
Impact Types Economic

 
Description AberForward graduate placement scheme
Amount £1,500 (GBP)
Organisation Aberystwyth University 
Sector Academic/University
Country United Kingdom
Start 01/2017 
End 02/2017
 
Description Farm advisor training session 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Industry/Business
Results and Impact Three farm advisor training sessions were held. Two at IBERS and one at SASA. The purpose is to make advisors aware of new developments and varieties in the pipeline, and provide advice about management of such new material.
Year(s) Of Engagement Activity 2018
 
Description Grasslands and Muck show 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Industry/Business
Results and Impact Demonstration plots at Grasslands and Muck Event
Year(s) Of Engagement Activity 2017
URL http://www.grasslandevent.co.uk/
 
Description Press briefing in London 
Form Of Engagement Activity A press release, press conference or response to a media enquiry/interview
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Media (as a channel to the public)
Results and Impact Industrial partner Germinal Holdings met with 5 journalists from the print media to give an update on projects.
Year(s) Of Engagement Activity 2018
 
Description Seed growers visit to IBERS 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Professional Practitioners
Results and Impact 15 seed growers visited IBERS for exchange of information and updates.
Year(s) Of Engagement Activity 2016
 
Description Show at Royal Welsh Grassland Event 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Professional Practitioners
Results and Impact Show at Royal Welsh Grasslands Event - 5000 farmers in attendance, the Germinal plots were a trailer stop on the tour around the site, it was an organic farm so disease pressure was high and the interest in the project was excellent. Interview conducted with S4C (In Welsh) and transmitted on their farming programme.
Year(s) Of Engagement Activity 2016
 
Description Training course at IBERS for 50 advisors 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Professional Practitioners
Results and Impact Training for advisors relating to forage crop breeding and grassland management
Year(s) Of Engagement Activity 2015,2016
 
Description Training course sponsored by Germinal Holdings for seed merchants 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Industry/Business
Results and Impact David Lloyd, IBERS legume breeder gave a presentation at a training course sponsored by Germinal Holdings for seed merchants
Year(s) Of Engagement Activity 2016
 
Description Training days for farm advisors 
Form Of Engagement Activity Participation in an open day or visit at my research institution
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Industry/Business
Results and Impact 2 x Farm advisor training days at IBERS (50 attendees) , explaining the importance of Drechslera, identifying the different types, explaining the economic cost and the expected outcomes of this project.
Year(s) Of Engagement Activity 2017
 
Description Training group of crop agronomists 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Industry/Business
Results and Impact Training a group of crop agronomists from Hutchinson's at Germinal Holdings Lincoln site
Year(s) Of Engagement Activity 2017
 
Description Visit of Advanced Ag 
Form Of Engagement Activity Participation in an open day or visit at my research institution
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Industry/Business
Results and Impact Visit of delegation of Advanced Ag from New Zealand, who has links with our industrial partner germinal Holdings to see the breeding work and facilities at IBERS and meet some of the staff involved in forage breeding
Year(s) Of Engagement Activity 2018
 
Description Visit of Farmlands NZ 
Form Of Engagement Activity Participation in an open day or visit at my research institution
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Industry/Business
Results and Impact Visit of Farmlands NZ who has links with Germinal Holdings our industrial partner. Primary purpose was to present the breeding work going on at IBERS and interact with the staff in the Forage Plant Breeding team
Year(s) Of Engagement Activity 2018