Speaker
Description
Climate change is one of the major challenges of the 21st century as the effects on the agricultural sector, are excepted to be massive, therefore jeopardizing food security. Among the climatic constraints, heatwaves have become more intense and more frequent which represent a threat to most crops, particularly during their reproductive stage which is the most critical period for seed yield and quality. Oilseed species such as oilseed rape and camelina are species mostly affected by heat stress, causing significant yield losses and a decreased seed nutritional and physiological quality. In this context, solutions to maintain sustainable productivity of these crops have been explored and rely on different levers. Varietal selection and improvement of crop management techniques are two main current levers to attempt either adapt to heat stress or alleviate its effects. However, they are limiting, especially because of genetic erosion (Esquinas-Alcázar 2005) and because their efficiency relies on the pedoclimatic conditions (Chen et al. 2005; Gao et al. 2021). This prompts agronomists and ecophysiologists to develop additional strategies that would explore the inherent ability of the plants to acclimate. Stress acclimation result from a sensitization to stress that allows organisms to respond to subsequent stresses and eventually overcome their negative effects. This priming effect is triggered by a based on a pre-stress exposure that can be similar or of different nature to the later stress. Thermopriming, which consists of applying moderate heat stress before a more intense heat stress, could help plants to acclimate following several mechanisms (Serrano et al. 2019; Balazadeh 2022; Liu et al. 2022). However, although acclimation has been widely described in terms of impacts on the development of aerial parts and on yield, very few studies have focused so far on its effects on root morphology and functions such as root exudation and the link between exudation and establishment of yield. In this study, we aimed at analyzing the effects of thermopriming not only on seed yield and quality but also on root morphology and exudation in oilseed rape and camelina. For this, at the onset of pod formation, we tested the effects of a moderate heat stress (pre-stress) consisting of a gradual increase in temperatures from 24 to 28°C for 5 days before an intense heat stress consisting of 5 days at 28°C with a daily heat peak of 5 hours at 33°C. First of all, our results showed that oilseed rape and camelina have contrasting strategies in terms of response to heat stress. Indeed, camelina seems to respond to the stress by increasing its investment to the roots by enhancing root prospection and modifying the quality of exudates, unlike oilseed rape, which seems to undergo heat stress by increasing the C exuded. Similar observations were made for seed yield and quality. Indeed, while heat stress had little effect on seed yield and quality in camelina, they were negatively impacted upon heat stress in oilseed rape. Moreover, these two species respond differently to the heat stress when they were previously exposed to the gradual increase, thus meaning they had contrasting acclimation strategies. In oilseed rape, thermopriming reduced C exudation and maintained yield and grain quality in comparison with heat stress alone, whereas it had a more negative impact on exudation and seed yield for camelina as a consequence of cumulated negative impacts of both temperature events.
| Keywords | Heat stress, Thermopriming, Root exudation, Seed yield and quality, Oilseed rape, Camelina |
|---|
