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Doctoral thesis2021Open access

A tale of two blights

Brouwer, Sophie


Potato is the third most important food crop for human consumption. However, the production is plagued by several pests and pathogens causing yield reducing diseases. Estimations indicate that 17% of the global potato yield is lost due to pests and pathogens. Considering the predicted growth of the human population and the already worrying prevalence of hunger, attenuation of these yield losses attributed to pests and pathogens is required. The major causal agents of disease in potato are the oomycete Phytophthora infestans and the fungus Alternaria solani, causing late blight and early blight respectively. The effective control of these two blights is achieved predominately by synthetic chemical fungicide treatments. However, even though currently effective, this reliance on chemical control is unsustainable and new knowledge is required for the development of future-proof control that takes the impact on the environment, human health and ecosystem dynamics into account. In this thesis, I studied the interactions between A. solani, P. infestans, and Solanum tuberosum. The main aim was to gain an increased understanding of the interactions between a single host plant and multiple pathogens, either alone or together. Using infection and transcriptomic studies of plant hormone deficient lines, I found that potato defences require intact salicylic acid signalling to limit A. solani infection. Additionally, I analysed the gene expression of both potato and A. solani during infection in more detail. Moreover, I analysed the spatial distribution of chemical elements in plants that were either susceptible or resistant to P. infestans and found several resistance specific redistribution patterns after inoculation with P. infestans. Finally, studies on the interactions between all three organisms, showed that the growth of P. infestans is limited in the presence of A. solani both in vitro and in planta. This holds true both in a controlled environment and in an agriculturally relevant setting. Overall, the work in this thesis has generated a deeper understanding of the interactions between potato and the two pathogens that cause the most significant losses in this crop. Furthermore, it highlights the importance of studying plant-pathogen interaction not solely as binary interactions and indicates potential new leads for the development of more sustainable control strategies.


Solanum tuberosum; potato; Phytophthora infestans; late blight; Alternaria solani; early blight; ionomics; co-infection; tripartite interactions

Published in

Acta Universitatis Agriculturae Sueciae
2021, number: 2021:3ISBN: 978-91-7760-684-0, eISBN: 978-91-7760-685-7
Publisher: Department of Plant Protection Biology, Swedish University of Agricultural Sciences

    UKÄ Subject classification

    Cell and Molecular Biology
    Food Science

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