S17 - Session O4 - Impacts of heat stress on seed quality in oilseed rape: analysis of the kinetic development of seed storage compounds.

Authors: Lethicia Magno Massuia de Almeida *, Jean-Christophe Avice, Annette Morvan-Bertrand, Nicolas Elie, Alain Mollier, Sophie Brunel-Muguet

Many studies point out the deleterious effect of high temperatures during the crop reproductive phase on seed yield and quality. However, the response of plants to repeated stressing events remains still poorly understood, especially in a context of climate change characterized by the increased frequency of extreme events, such as spring and summer heat waves. Although genetic improvement and management practices are relevant tools of adaptation strategies, our study aims at providing insights of stress memory effect in acclimation schemes. Indeed, plant acclimation to recurring stresses is likely to occur through a priming process, which corresponds to the exposition to a period of moderate stress preceding a more intense event (Crisp et al., 2016). Our prior results in oilseed rape (Magno et al., 2021) have shown that an effective priming sequence must consider (i) the optimal temperature of the compound biosynthesis process and (ii) the synchrony between the thermo-sensitizing event and the period of biosynthesis of the targeted storage compound (Baud et al., 2002). We observed that an early moderate stress (at the beginning of seed filling) that preceded a more intense stress exposure had a positive effect only on the seed nitrogen concentration and a soluble sugar ratio used as a proxy of seed desiccation tolerance. Based on these conclusions, we performed an additional experiment to further study the kinetics of the seed compounds evolution by combining biochemical and histological approaches, which has never been done before in oilseed rape under heat stress conditions. In the present study, we analyzed the responses of oilseed rape plants subjected to three heat stress sequences that differed in the intensity of the thermal event, the timing of application, the duration and the frequency. Harvests throughout the development and maturation phases were performed to monitor the evolution of the main storage compounds used to determine seed nutritional and physiological quality in oil crops i.e. fatty acids, proteins and soluble sugars which are the major criteria for edible oil and cakes used in human and animal consumption. Our analyses should provide a better understanding of the compound specific critical periods in terms of timing, duration and intensity, in the perspective of providing priming protocols to maintain or even increase seed quality under climate change conditions.