Understanding interactions between fungal pathogens Leptosphaeria maculans (phoma stem canker) and Pyrenopeziza brassicae (light leaf spot) on oilseed rape

Diseases of arable crops are major threats to food production in the agricultural industry. Phoma stem canker and light leaf spot are two economically important diseases of oilseed rape in the UK. These two diseases can cause annual yield losses of winter oilseed rape > £100M. Phoma stem canker is mainly caused by the fungal pathogen Leptosphaeria maculans and light leaf spot is caused by the fungal pathogen Pyrenopeziza brassicae. Epidemics of both diseases are initiated by ascospores released from crop debris from the previous cropping season. However, interactions between these two pathogens during ascospore production are unknown. Ascospores of both pathogens initially cause leaf lesions, then either grow to the stem causing stem canker (L. maculans) or produce conidia causing secondary infection (on leaves, stems and pods) (P. brassicae). Although co-infections by these two pathogens were observed in crops, the interactions between them during leaf infection are not known. Results of our recent work showed that cultivars with good resistance against L. maculans are susceptible to P. brassicae. There is a need to understand the plant defence response to these two major pathogens and identify sources for resistance against both pathogens of oilseed rape. East Anglia is a major oilseed rape growing area in the UK. This PhD project aims to understand interactions between these two fungal pathogens at different stages of their life cycles and to develop new tools to control them. To achieve this, there are four related objectives: (1) To investigate interactions between the two pathogens (L. maculans and P. brassicae) during production of ascospores; (2) To study their interactions during leaf infection; (3) To examine their interactions in field conditions on different cultivars; (4) To develop new strategies for better control of both pathogens.