S03 - Session P1 - Pathogen transmission by the seed. The necrotrophic fungus Alternaria brassicicola might hijack immune response in Arabidopsis germinating seeds for its own propagation

Authors: Mailen Ortega-Cuadros *, Nubia Velasquez, Tiago Lodi De Souza, Romain Berruye2, Sophie Aligon, Sandra Pelletier, Jean-Pierre Renou, Tatiana Arias, Claire Campion, Thomas Guillemette, Jérôme Verdier and Philippe Grappin

The caper is an important plant in the Mediterranean area, tolerant to drought, used for its flower buds and fruits, and recently for its bioactive principles. The seeds present a low germination percentage (G), which has been related to physiological dormancy when responding positively to treatments with gibberellic acid solution (GA 3 ). The objective of this study was to provide practical guidelines for gibberellins use to improve G, for which 3 experiments were carried out. In the first experiment, 2 GA 3 application methods (moistening the germination substrate of the Between-Paper method with a GA 3 and immersion in the GA 3 ) and 5 GA 3 concentrations (0, 100, 500, 1000 and 2000 mg·L -1 ) were compared. The best result was obtained by moistening the substrate with 500 mg·L -1 (G=76.3%). In the second experiment, different methods for moistening the substrate with a 500 mg·L -1 GA 3 were compared. The method of continuous wetting, used in the first experiment, was compared to changing the germination substrate fortnightly and with moistening the substrate with GA 3 for 30 days and with ultra-pure-water afterwards. The best result was obtained by changing the substrate or moistening it with GA 3 only for 30 days (G=84.2%). In the last experiment, lower GA 3 and technical gibberellins (A 4 and A 3 ) concentrations were compared (0, 0.1, 1, 5, 10 and 50 mg·L -1 ). A 4 led to higher G than control, even at the lowest concentration, and the best results were achieved from 5 mg·L -1 without significant differences between concentrations (up to G=92.5%). Overall, it can be stated that to improve caper seed germination it is recommended to apply an A 4 solution at low concentrations (minimum 5 mg·L -1 ) or to use a 500 mg·L -1 GA 3 , replacing the germination substrate fortnightly, or to apply such solution for 30 days, and then continue to moisten the substrate with ultra-pure-water.