Cécile Thomas

Thesis started in 2016, defended in march, 21^th 2019
Funding: Bourse Cifre, Bretagne-Plants Innovation

Direction: Florence Val, Didier Andrivon

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Abstract:

The national regulation (Ecophyto II plan) requires pesticide reduction. Thus, it is crucial to develop alternative control methods, particularly to protect potato crops, highly dependent on agrochemicals. The management of Phytophthora infestans, responsible for potato late blight, requires the application of about 15 fungicide treatments per cropping season. Using the combination of the quantitative and induced resistance, could be a positive strategy. This method requires a better understanding of Solanum tuberosum - P. infestans interactions. To this end, this PhD thesis investigated the effect of induced resistance in potato on P. infestans ecology. Plant physiological responses were opposed to the pathogen life history traits and effectors. Four potato genotypes with different resistance levels were treated with a concentrated culture filtrate (CCF) of P. infestans inducing PAMP-triggered immunity. Then, detached leaflets were inoculated with fast- and slow-growing strains of P. infestans. The expression of 14 potato defense genes and of 9 P. infestans effector genes was analyzed by qRT-PCR. Disease symptoms were assessed by manual measurements and by visible and fluorescence image analysis. The main results obtained showed that the effectiveness of induced defenses by CCF depends on the genotype/strain pair according to (i) the genotype inducibility via the expression of PR protein (ii) the P. infestans growth rate and the expression of its effectors. High throughput phenotyping confirmed that, after induction, the symptom reduction was specific to both genotype and strain. Genotypes inducibility and their resistance to different strains of P. infestans could be considered for plant breeding in order to increase the effectiveness of induced resistance.

Poster (pdf)