Determination of the pathogen population structure of Pyrenopeziza brassicae, causal agent of light leaf spot on brassicas

Light leaf spot, caused by the fungal pathogen Pyrenopeziza brassicae, is currently the major disease problem in oilseed rape production in the UK. Furthermore, P. brassicae can also be found on vegetable brassicas such as cabbage, cauliflower and Brussels sprouts. It is still unknown if the same strains of the pathogen are able to infect both oilseed rape and vegetable brassicas. Effective control of light leaf spot is difficult to achieve. Chemical control of the disease is challenging as fungicides must be applied when the pathogen grows symptomless in plant tissue (Figueroa et al., 1994). Exploiting plant resistance against the pathogen could help control the disease but current commercial cultivars show poor light leaf spot resistance. The aim of the project is to identify the pathogen population structure, to determine if the same strains are able to infect oilseed rape and other brassicas, and to gain a better understanding of the plant–pathogen interactions. Therefore, isolates of P. brassicae are being collected from infected leaf (oilseed rape, vegetables) and bud tissue (Brussels sprouts) from nine cultivars, which have been drilled at four sites in England (Cambridgeshire, Herefordshire, Lincolnshire, Yorkshire) and one site in Scotland (Aberdeenshire). The isolates will be studied morphologically and molecularly using neutral markers to determine differences between the isolates. Certain isolates will be used for in planta screenings to investigate differential interactions between isolates and potential host cultivars