16AGRITECHCAT5: Integrated control of Leptosphaeria pathogens on UK winter oilseed rape

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Phoma stem canker is an economically important disease of oilseed rape in the UK, leading to annual yield losses > £100M. This disease is caused by two closely related pathogens: Leptosphaeria biglobosa and L. maculans. However, current control of this disease focuses only on L. maculans and does not account for epidemics caused by L. biglobosa. This is one reason why this disease still causes substantial yield losses in the UK, despite the use of fungicides costing £20 M p.a. Results of recent work showed that L. biglobosa can be as destructive as L. maculans and that L. biglobosa is less sensitive to triazole fungicides than L. maculans. Therefore, L. biglobosa is a growing threat to oilseed rape production in the UK since no methods have been developed to control it. Previous research has mainly focused on improving control of L. maculans by both cultivar resistance and fungicides and little work has been done on control of L. biglobosa. The aims of this project are to understand stem canker epidemics caused by L. biglobosa and to develop new strategies for better control of phoma stem canker by targeting both causal pathogens (L. biglobosa and L. maculans). This project will use molecular techniques to investigate the differences between different regions in proportions of L. biglobosa and L. maculans in pathogen populations from air samples and differences in proportions of L. biglobosa and L. maculans in oilseed rape stems with severe canker symptoms sampled from different field trials and farmer's fields. Results will be used to guide deployment of cultivars with suitable resistance for the region where the corresponding pathogen species (L. biglobosa or L. maculans) is predominant. Control of severe stem canker epidemics involves fungicides. However, current fungicide control targets only L. maculans and has relied on use of triazole fungicides. Recent work showed that L. biglobosa is less sensitive to triazole fungicides than L. maculans. This project will investigate efficacy of triazole and non-triazole fungicides for control of L. biglobosa as well as L. maculans. The new knowledge about efficacy of different fungicides for control of the two pathogens, combined with the information about proportions of L. biglobosa and L. maculans in pathogen populations, will enable better control of the disease by targeted fungicide application. This project will also investigate the mechanisms of changes in sensitivity to different fungicides in L. biglobosa and L. maculans. The new knowledge will be used to guide use of existing fungicides and development of new fungicides.Use of host resistance is an effective and environmentally friendly way to control plant diseases. However, previous work on oilseed rape resistance against phoma stem canker has been focused on resistance against L. maculans with no work done on resistance against L. biglobosa. This project will assess cultivars and pre-breeding material for resistance against L. biglobosa and use recent developments in genomics to identify candidate resistance genes. This will provide new knowledge for improving breeding and using cultivar resistance to control the disease.New knowledge obtained from this project about the two causal pathogens, host resistance and efficacy of different fungicides for controlling them will be used to develop integrated control strategies for better control of phoma stem canker. This project will benefit growers by reducing yield losses through development of effective control methods targeting both pathogens. It will also address the challenge of food security. The environment will also benefit from reduced use of fungicides through targeted fungicide applications.