Phoma stem canker is a damaging disease of oilseed rape in the UK, leading to yield losses > £100M p.a. despite the use of fungicides. This disease is caused by two related pathogens: Leptosphaeria maculans and L. biglobosa. However, current control of the disease focuses only on L. maculans. Recent work showed that L. biglobosa can cause substantial yield losses and that it is less sensitive to triazole fungicides than L. maculans. L. biglobosa is a threat to oilseed rape production in the UK since no methods have been developed to control it. This project will investigate stem canker epidemics caused by L. biglobosa, determine the proportions of L. biglobosa and L. maculans in pathogen populations, screen cultivar resistance against L. biglobosa, determine efficacy of different fungicides for control of L. biglobosa as well as L. maculans. The new knowledge about the pathogens, host resistance and efficacy of fungicides will be used to develop new control strategies that ensure both pathogens are targeted.

Free Living Nematodes (FLN) are emerging as a major problem for UK potato growers, exacerbated in the short term by removal of approved nematicides and in the long-term by expected population increases due to climate change. FLN cause direct damage by feeding on potato roots reducing yields and quality, and indirectly by transmitting Tobacco Rattle Virus (TRV). Relatively low levels of TRV infections can render entire crops unsaleable, both for the fresh and the processing industries. Current knowledge estimates the total loss to the UK potato industry to be >£13m p.a. FLN comprise a range of different taxonomic groups that are difficult to distinguish visually but vary significantly in terms of their distribution, pathogenicity and virus transmission frequencies, and have been to date under-studied in the UK. The problem is further compounded by beneficial and pathogenic FLN species co-existing, and thus accurate discrimination is essential. This project brings together a consortium of companies with a grower base of over 500 growers invloved in ware potato production seed both for use in the UK and export. In addition, a number of companies with potential methods for controlling FLN populations are included as partners. For the first time, a molecular diagnostic capable of distinguishing between the three main groups of FLN of interest will be developed, validated and deployed. This will be used to assess direct FLN feeding damage on a selection of commercial potato varieties as well as study effects on tuber quality and transmission of virus. In parallel, molecular markers will be developed to facilitate the breeding of new potato varieties with resistance to TRV.

Despite fungicide applications valued at over £25M, 'Rhynchosporium' continues to be the most problematic and economically damaging disease of barley leading to annual yield losses of ~£7M. Research has shown the importance of extensive growth of this pathogen before symptoms are visible, even on resistant cultivars, and this has changed our understanding of its epidemiology. Previously we based our understanding of resistance on visible symptoms only - this new knowledge explains some of the difficulties in managing the disease. Understanding the impact of pre-symptomatic colonisation on yield and its impact on disease management is pivotal and our breeding and crop protection strategies need to change to exploit this new knowledge. We will identify, characterise and combine sources of barley resistance to improve durability and use knowledge of the mode of action of different defence mechanisms to improve crop protection strategies to increase the effectiveness of currently available fungicides. Using host plant gene markers together with microscopy methods using fluorescently-tagged pathogen isolates we will characterise sources of resistance, identify candidate genomic locations and obtain flanking diagnostic molecular markers. This knowledge will be used to develop new varieties and to validate optimal disease management programmes against this important pathogen.