Award details

Understanding resistance to decrease risk of severe phoma stem canker on oilseed rape

Reference	BB/I017585/1
Principal Investigator / Supervisor	Professor Bruce Fitt
Co-Investigators / Co-Supervisors	Dr Yongju Huang, Professor Graham King
Institution	Rothamsted Research
Department	Plant Pathology and Microbiology
Funding type	Research
Value (£)	516,062
Status	Completed
Type	Research Grant
Start date	01/12/2010
End date	01/07/2011
Duration	7 months

Abstract

This project is using oilseed rape (Brassica napus)/Leptosphaeria maculans (phoma stem canker disease as a model host/pathogen system to improve understanding of operation of host resistance for effective control of plant diseases. Phoma stem canker poses an increasing threat to sustainable production of oilseed rape. This project aims to decrease future risk of severe phoma stem canker on oilseed rape to maintain yield to contribute to food security. R gene mediated resistance to L. maculans is race-specific and is often rendered ineffective in 2 to 3 years due to evolution of pathogen populations from avirulence to virulence. Seasonal/regional changes in distribution of races of L. maculans will be identified using traditional cotyledon tests or new quantitative PCR. The L. maculans race information will be used to guide regional and seasonal deployment of different R genes to maintain their effectiveness. This project will assess effectiveness of R gene resistance and quantitative resistance in natural conditions and controlled environments. Cultivars with only R genes, only quantitative resistance or combinations of R gene & quantitative resistance will be used to investigate which R gene or which combination of resistance is more consistently effective in different environments. This will guide breeders to produce cultivars with resistance effective in a changing environment. Three R genes show a differential response to temperature; two of them map in the same region at distinct loci on chromosome A10. This project will focus on these R genes and use temperature as a means to understand operation of B. napus resistance to L. maculans. To investigate whether the difference in temperature response between these R genes is due to the resistance loci or host background, by collaboration with China and Canada, sets of materials with these R genes in the same background or the same R gene in different backgrounds will be tested at different temperatures.

Summary

Use of host resistance is the most effective and environmentally friendly way to control plant diseases. Oilseed rape (Brassica napus) is an important arable crop in the UK. The disease phoma stem canker, caused by Leptosphaeria maculans, poses an increasing threat to sustainable production of this crop. In the UK, phoma stem canker cause losses of > £100M p.a., despite use of fungicides. These losses will increase if the most effective fungicides are no longer permitted by EU legislation. Furthermore, it is predicted that global warming will continue to increase the range and severity of phoma stem canker epidemics. There is thus a challenge to produce cultivars with effective resistance in a changing climate to contribute to national food security. This project aims to decrease future risk of severe phoma stem canker on oilseed rape by developing a scheme for effective use of host resistance and by improving understanding of operation of host resistance against the pathogen to guide resistance breeding. The two types of resistance to L. maculans identified in B. napus are major resistance (R) gene mediated qualitative resistance that operates in cotyledons and leaves in autumn and quantitative resistance that operates in leaf stalk and stem tissues, after initial leaf infection until harvest in summer. R gene mediated resistance to L. maculans is single-gene race-specific resistance that is effective in protecting plants only if the corresponding avirulent allele is predominant in the local L. maculans population. R gene resistance often loses its effectiveness in 2 to 3 years after widespread use in commercial cultivars because of changes in L. maculans populations. To maintain the effectiveness of R gene resistance and decrease the risk that it will become ineffective, races in L. maculans populations in different regions will be determined. The L. maculans race information will be used to develop a scheme for deployment of cultivars with differentR genes in space and time. Previous work at Rothamsted showed that temperature influences the effectiveness of both R gene resistance and quantitative resistance against L. maculans. To identify effective resistance in oilseed rape that will operate against L. maculans in a changing climate, this project will assess effectiveness of different types of resistance in both in controlled environments and natural conditions. Cultivars with only R genes, only quantitative resistance or combinations of R gene & quantitative resistance will be tested in different environments. From the results, we can assess which R gene or which combination of resistance is more effective. This information can be used to improve breeding strategies. To understand how temperature influences the effectiveness of host resistance, this project will focus on the three R genes which show a differential response to temperature; two of them map in the same region on chromosome A10 at distinct loci. To investigate mechanisms of operation of R gene and quantitative resistance against L. maculans, sets of materials with these R genes in the same background or the same R gene in different backgrounds will be used. These materials will enable us to investigate whether the difference in temperature response between these three R genes is due to the resistance loci or host background. Results from this project will help to minimise the risk of severe epidemics on oilseed rape so that yields are maintained to contribute to national food security and avoid unnecessary fungicide use. Breeders will benefit from improved strategies for breeding cultivars with effective disease resistance. The environment will also benefit from reduced greenhouse gas emissions through improved disease control in oilseed rape.

Impact Summary

This project is directly relevant to the BBSRC Strategic Research Priority 1, Food Security, outlined in the 2010-2015 Strategic Plan. Oilseed rape is an important arable crop in the UK. The greatest current threat to sustainable production of this crop is the disease phoma stem canker caused by Leptosphaeria maculans. This project will benefit the agricultural industry by decreasing future risk of severe phoma stem canker through improved understanding of resistance to L. maculans. A major beneficiary of the project will be plant breeders. The project will investigate effects of environmental factors (e.g. temperature) on stability of different types of resistance (e.g. R gene mediated resistance and quantitative resistance) to L. maculans which will provide breeders with information for selection of pre-breeding material and guide their breeding strategies for development of suitable cultivars for different environments. In addition, this project will develop molecular markers for specific resistance loci that can be used by breeders in marker-assisted breeding programmes. This project will produce information on regional distribution of L. maculans races which will help breeders to develop cultivars for target regions. Another major beneficiary of the project will be growers. This project will improve understanding of operation of host resistance and knowledge about current L. maculans races to develop a scheme for deployment of cultivars with different combinations of R genes and background quantitative resistance, so that growers can choose suitable cultivars and avoid unnecessary fungicide use, especially if recent EU legislation leads to a decrease in fungicide types available. Furthermore, it is predicted that global warming will continue to increase the UK range and severity of phoma stem canker epidemics. This project will help growers to use resistance more effective for more sustainable and profitable control of phoma stem canker in oilseedrape. Agricultural advisors will benefit from this project by using the results to make recommendations on effective use of host resistance. HGCA will benefit by using the results to decrease costs of Recommended List trials. Policy-makers will benefit by using the results to guide forward planning as part of strategies to achieve the government climate change mitigation target for UK agriculture (Food 2030, Jan 2010) by reducing its carbon foot-print through improved disease control. Ultimately the public and environment will benefit from reduced fungicide use through improved guidance on selection and deployment of host resistance. Furthermore, improved resistance for efficient disease control in oilseed rape crops will increase yield, which will contribute to national food security. Since phoma stem canker is not only a major disease problem on oilseed rape in the UK but also a global disease on oilseed rape and brassica vegetables, results from this project will also contribute to international food security. The involvement of wide range of partners in this LINK project will ensure that outcomes of this research are exploited directly to translate scientific outputs into practical improvements to current disease management strategies. Well-established web-based communication methods will disseminate the research results quickly to the scientific communities (e.g. Leptosphaeria Research Community and Brassica Research Community). This project will produce new host materials with different resistance genes in the same background or the same resistance gene in different backgrounds. These materials will be ideal for further detailed investigation of mechanisms of host-pathogen interactions under different environment conditions. Therefore, this project will benefit scientific communities by improving our understanding of host resistance.

Committee	Research Committee B (Plants, microbes, food & sustainability)
Research Topics	Crop Science, Microbiology, Plant Science
Research Priority	Crop Science, Living with Environmental Change
Research Initiative	LINK: Sustainable Arable Production SAPPIO (SAP) [1998-2010]
Funding Scheme	X – not Funded via a specific Funding Scheme

Associated awards:

BB/I017585/2 Understanding resistance to decrease risk of severe phoma stem canker on oilseed rape

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