Dr Celine Caseys of the University of California, Davis, delivered the third presentation in the FABI International Seminar Series on 30 July. Her seminar “Plant versus Botrytis: A story of quantitative plant-pathogen interactions” highlighted how the quantitative virulence of 98 strains of Botrytis varies across eight crops representing 90 genotypes. FABI co-hosted the online seminar with the Southern African Society for Plant Pathologists(SASPP). SASPP President Prof. Wijnand Swartsaid the seminar series had “set a new era for SASPP and plant pathologists to interact on a global stage”. 

Dr Caseys showed how quantitative virulence gives clues to how Botrytis cinerea (the cause of grey mould), a polyphagous fungal pathogen that causes necrotic disease on various plant hosts, results in symptoms on eight plant hosts. Her study showed different responses of tomato, sunflower, endive, chicory, lettuce, soybean and turnip infected with B. cinerea compared to Arabidopsis plants. 

Dr Caseys infected the leaves of the seven crop species with B. cinerea, which then developed lesions. She used the lesion area as a quantitative measurement of the plants’ interaction with the pathogen. She investigated the influence of factors such as human crop breeding and the leaf surfaces infected by the pathogens on the severity of disease symptoms. Her study showed that domesticity had a “significant but small effect” on susceptibility to the pathogen and that human crop breeding did not change the plants’ susceptibility to Botrytis. Wild plant genotypes tend to be slightly more susceptible, she said.

Dr Caseys concluded that quantitative virulence was “real and complex” and that “both plant resistance and fungal virulence have quantitative genetic architectures with components of small to moderate effects”. The interaction of these quantitative architectures, she said, generate diverse disease outcomes.  

In the interest of ongoing science engagement, FABI hosts free monthly virtual seminars on a wide range of topics related to plant health. Participation is free and open to registered participants. One needs to register once to take part and to receive updates on upcoming seminars.