Modelling Memory: do crop models need to become nostalgic?

International audienceIncreased frequency of stress events such as heat waves has been observed for the last decades. Based on the last IPCC report, they are expected to be more frequent, to last longer and to increase in intensity during the reproductive phase of economically important crops. Many recent studies pointed out induced memory effects of stressing events when plants are challenged several times with similar stresses throughout the crop season. These memory effects were shown to be potentially beneficial since the plants are 'primed' and thus more prepared to develop an earlier, more rapid, intense and/or sensitive response when the stress recurs [1]. Therefore, the new climatic patterns prompts to take into account stress memory into predictive crop modelling approaches so as to estimate the effects of repeated stresses and their consequences on crop yield, quality of harvested products. During the last decades, the use of crop models have been enlarged to climate change driven predictions [2]. While evidence for improving crop climate models and especially the temperature response functions in order to reduce uncertainty in yield simulations before any decision making in agriculture, no modelling studies have attempted to decipher and interpret simulation bias in the light of stress memory nor they focused on methodologies to take into account stress memory effects

Modelling Memory: do crop models need to become nostalgic?

International audienceIncreased frequency of stress events such as heat waves has been observed for the last decades. Based on the last IPCC report, they are expected to be more frequent, to last longer and to increase in intensity during the reproductive phase of economically important crops. Many recent studies pointed out induced memory effects of stressing events when plants are challenged several times with similar stresses throughout the crop season. These memory effects were shown to be potentially beneficial since the plants are 'primed' and thus more prepared to develop an earlier, more rapid, intense and/or sensitive response when the stress recurs [1]. Therefore, the new climatic patterns prompts to take into account stress memory into predictive crop modelling approaches so as to estimate the effects of repeated stresses and their consequences on crop yield, quality of harvested products. During the last decades, the use of crop models have been enlarged to climate change driven predictions [2]. While evidence for improving crop climate models and especially the temperature response functions in order to reduce uncertainty in yield simulations before any decision making in agriculture, no modelling studies have attempted to decipher and interpret simulation bias in the light of stress memory nor they focused on methodologies to take into account stress memory effects

Effets des stress thermiques répétés sur le rendement et la qualité grainière du colza : caractérisation écophysiologique et modélisation

Many studies have shown the deleterious effects of heat stress during the reproductive phase of plants, which are particularly detrimental on the yield and quality of harvested products in field crops. However, in a context of climate change characterised by the increased frequency of spring and summer heat waves, the response of crops to repeated heat stresses remains poorly studied and the interpretation of their effects scarcely consider the possibility of stress memory effects which modify crop responses to later stresses. These memory effects can be either positive owing to a priming effect or negative as a consequence of amplified effects of successive stresses. Indeed, it has been shown that it is possible to sensitise plants through a period of exposition to a moderate stress preceding a more intense stress by the beneficial effect of stress memory. In this work, we tested several thermal stress protocols in oilseed rape differing in intensity, period of exposure, duration and frequency under controlled conditions, with the aim of characterising the plant responses to repeated stresses during the crop cycle (intragenerational effects) and over two generations of stressed plants (intergenerational effects). Our ecophysiological characterisation works show that the effects of repeated heat stresses are not significant on total yield due to compensation phenomena reflecting the plasticity of the oilseed rape, in contrast to the effects on seed quality criteria. These effects decrease the fatty acid content, modify the proportion of monounsaturated fatty acids at the expense of polyunsaturated fatty acids (i.e. increase in the ω6:ω3 ratio) and lead to a degradation of the physiological quality of the seeds (i.e. loss of membrane integrity, acceleration of germination and increase of dormancy). Our results also indicated that a moderate stress preceding a more intense late stress had a beneficial effect only on seed nitrogen content and a ratio of oligosaccharides of the raffinose family, which is an indicator of seed desiccation tolerance. With the aim of improving crop performances in the context of climate change, thermopriming protocols could be proposed to targeted major seed quality compounds. Therefore, these protocols must consider (i) the optimal temperature for the compound synthesis process and (ii) the synchronisation between the thermal event which is expected to have a priming effect and the synthesis/maturation period of the targeted compound. In parallel to this ecophysiological characterisation, we tested three modelling approaches (i.e. ecoclimatic indicators, a (semi-) mechanistic crop model and two data mining methods) which highlighted (i) the non-additive effects of repeated thermal stresses and (ii) the need to improve the temperature functions within mechanistic crop models. Our modelling study is a proof of concept of the need to consider stress memory in predictive crop models, which demonstrates the need to implement the current models in order to better estimate the effects of repeated thermal stresses and their consequences on the yield and quality of harvested products.De nombreuses études font le constat des effets délétères du stress thermique pendant la phase reproductrice des végétaux, ce qui est préjudiciable au rendement et à la qualité des produits récoltés chez les espèces de grandes cultures. Cependant, dans un contexte de changement climatique caractérisé par une fréquence accrue des vagues de chaleur printanières et estivales, la réponse des cultures à la répétition des stress thermiques reste encore peu étudiée et leur interprétation ne prend pas souvent en compte la possibilité d’un effet mémoire du stress modifiant la réponse des cultures à des stress ultérieurs. Cet effet mémoire peut être bénéfique grâce à un effet priming atténuant ou négatif par un effet amplificateur des stress successifs. En effet, il a été démontré qu’il était possible de sensibiliser les plantes grâce à une période de stress modéré précédant un stress plus intense par l’effet bénéfique de la mémoire du stress. Dans le cadre de cette thèse, nous avons testé plusieurs protocoles des stress thermiques chez le colza, différant par leur intensité, la période d’exposition, la durée et la fréquence en conditions contrôlées, dans l’objectif de caractériser les réponses des plantes aux stress répétés pendant le cycle de la culture (effets intragénérationnels) et au cours de deux générations de plantes stressées (effets intergénérationnels). Nos travaux de caractérisation écophysiologique montrent que les effets des stress thermiques répétés ne sont pas significatifs sur le rendement total du fait des phénomènes de compensation reflétant la plasticité du colza, à la différence des effets sur les critères de qualité grainière. Ces effets diminuent la teneur en acides gras, modifient les proportion d’acides gras monoinsaturés au détriment des acides gras polyinsaturés (i.e. augmentation du ratio ω6:ω3) et conduisent à une dégradation de la qualité physiologique des graines (i.e. perte de l'intégrité membranaire, accélération de la germination et augmentation de la dormance). Nos résultats ont également indiqué qu’un stress modéré précédant un stress tardif plus intense avait un effet bénéfique, mais uniquement sur la teneur en azote des graines et un ratio d’oligosaccharides de la famille du raffinose, indicateur de la tolérance à la dessiccation. Dans des perspectives d’amélioration des performances des cultures face au changement climatique, des protocoles thermo-sensibilisants pourraient être proposés en ciblant des composés majeurs de la qualité grainière. Ainsi, les protocoles thermo-sensibilisants envisageables doivent prendre en compte (i) la température optimale au processus de synthèse du composé ; et (ii) la synchronisation entre l’événement thermique ayant un effet bénéfique et la période de synthèse/maturation du composé ciblé. En parallèle à ce travail de caractérisation écophysiologique, nous avons testé trois approches de modélisation (i.e. indicateurs écoclimatiques, un modèle de culture (semi-) mécaniste et deux méthodes de fouille de données) qui ont mis en évidence (i) les effets non additifs des stress thermiques répétés et (ii) la nécessité d’améliorer les fonctions de température au sein des modèles de culture mécanistes. Notre travail de modélisation est une preuve de concept sur la nécessité de considérer la mémoire du stress dans les modèles prédictifs des performances culturales, qui démontre le besoin de faire évoluer les modèles actuels pour mieux estimer les effets des stress thermiques répétés et leurs conséquences sur le rendement et la qualité des produits récoltés

Εffects of repeated heat stress on yield and seed quality in Brassica napus L. : ecophysiological characterization and modelling

De nombreuses études font le constat des effets délétères du stress thermique pendant la phase reproductrice des végétaux, ce qui est préjudiciable au rendement et à la qualité des produits récoltés chez les espèces de grandes cultures. Cependant, dans un contexte de changement climatique caractérisé par une fréquence accrue des vagues de chaleur printanières et estivales, la réponse des cultures à la répétition des stress thermiques reste encore peu étudiée et leur interprétation ne prend pas souvent en compte la possibilité d’un effet mémoire du stress modifiant la réponse des cultures à des stress ultérieurs. Cet effet mémoire peut être bénéfique grâce à un effet priming atténuant ou négatif par un effet amplificateur des stress successifs. En effet, il a été démontré qu’il était possible de sensibiliser les plantes grâce à une période de stress modéré précédant un stress plus intense par l’effet bénéfique de la mémoire du stress. Dans le cadre de cette thèse, nous avons testé plusieurs protocoles des stress thermiques chez le colza, différant par leur intensité, la période d’exposition, la durée et la fréquence en conditions contrôlées, dans l’objectif de caractériser les réponses des plantes aux stress répétés pendant le cycle de la culture (effets intragénérationnels) et au cours de deux générations de plantes stressées (effets intergénérationnels). Nos travaux de caractérisation écophysiologique montrent que les effets des stress thermiques répétés ne sont pas significatifs sur le rendement total du fait des phénomènes de compensation reflétant la plasticité du colza, à la différence des effets sur les critères de qualité grainière. Ces effets diminuent la teneur en acides gras, modifient les proportion d’acides gras monoinsaturés au détriment des acides gras polyinsaturés (i.e. augmentation du ratio ω6:ω3) et conduisent à une dégradation de la qualité physiologique des graines (i.e. perte de l'intégrité membranaire, accélération de la germination et augmentation de la dormance). Nos résultats ont également indiqué qu’un stress modéré précédant un stress tardif plus intense avait un effet bénéfique, mais uniquement sur la teneur en azote des graines et un ratio d’oligosaccharides de la famille du raffinose, indicateur de la tolérance à la dessiccation. Dans des perspectives d’amélioration des performances des cultures face au changement climatique, des protocoles thermo-sensibilisants pourraient être proposés en ciblant des composés majeurs de la qualité grainière. Ainsi, les protocoles thermo-sensibilisants envisageables doivent prendre en compte (i) la température optimale au processus de synthèse du composé ; et (ii) la synchronisation entre l’événement thermique ayant un effet bénéfique et la période de synthèse/maturation du composé ciblé. En parallèle à ce travail de caractérisation écophysiologique, nous avons testé trois approches de modélisation (i.e. indicateurs écoclimatiques, un modèle de culture (semi-) mécaniste et deux méthodes de fouille de données) qui ont mis en évidence (i) les effets non additifs des stress thermiques répétés et (ii) la nécessité d’améliorer les fonctions de température au sein des modèles de culture mécanistes. Notre travail de modélisation est une preuve de concept sur la nécessité de considérer la mémoire du stress dans les modèles prédictifs des performances culturales, qui démontre le besoin de faire évoluer les modèles actuels pour mieux estimer les effets des stress thermiques répétés et leurs conséquences sur le rendement et la qualité des produits récoltés.Many studies have shown the deleterious effects of heat stress during the reproductive phase of plants, which are particularly detrimental on the yield and quality of harvested products in field crops. However, in a context of climate change characterised by the increased frequency of spring and summer heat waves, the response of crops to repeated heat stresses remains poorly studied and the interpretation of their effects scarcely consider the possibility of stress memory effects which modify crop responses to later stresses. These memory effects can be either positive owing to a priming effect or negative as a consequence of amplified effects of successive stresses. Indeed, it has been shown that it is possible to sensitise plants through a period of exposition to a moderate stress preceding a more intense stress by the beneficial effect of stress memory. In this work, we tested several thermal stress protocols in oilseed rape differing in intensity, period of exposure, duration and frequency under controlled conditions, with the aim of characterising the plant responses to repeated stresses during the crop cycle (intragenerational effects) and over two generations of stressed plants (intergenerational effects). Our ecophysiological characterisation works show that the effects of repeated heat stresses are not significant on total yield due to compensation phenomena reflecting the plasticity of the oilseed rape, in contrast to the effects on seed quality criteria. These effects decrease the fatty acid content, modify the proportion of monounsaturated fatty acids at the expense of polyunsaturated fatty acids (i.e. increase in the ω6:ω3 ratio) and lead to a degradation of the physiological quality of the seeds (i.e. loss of membrane integrity, acceleration of germination and increase of dormancy). Our results also indicated that a moderate stress preceding a more intense late stress had a beneficial effect only on seed nitrogen content and a ratio of oligosaccharides of the raffinose family, which is an indicator of seed desiccation tolerance. With the aim of improving crop performances in the context of climate change, thermopriming protocols could be proposed to targeted major seed quality compounds. Therefore, these protocols must consider (i) the optimal temperature for the compound synthesis process and (ii) the synchronisation between the thermal event which is expected to have a priming effect and the synthesis/maturation period of the targeted compound. In parallel to this ecophysiological characterisation, we tested three modelling approaches (i.e. ecoclimatic indicators, a (semi-) mechanistic crop model and two data mining methods) which highlighted (i) the non-additive effects of repeated thermal stresses and (ii) the need to improve the temperature functions within mechanistic crop models. Our modelling study is a proof of concept of the need to consider stress memory in predictive crop models, which demonstrates the need to implement the current models in order to better estimate the effects of repeated thermal stresses and their consequences on the yield and quality of harvested products

Effets des stress thermiques répétés sur le rendement et la qualité grainière du colza : caractérisation écophysiologique et modélisation

Many studies have shown the deleterious effects of heat stress during the reproductive phase of plants, which are particularly detrimental on the yield and quality of harvested products in field crops. However, in a context of climate change characterised by the increased frequency of spring and summer heat waves, the response of crops to repeated heat stresses remains poorly studied and the interpretation of their effects scarcely consider the possibility of stress memory effects which modify crop responses to later stresses. These memory effects can be either positive owing to a priming effect or negative as a consequence of amplified effects of successive stresses. Indeed, it has been shown that it is possible to sensitise plants through a period of exposition to a moderate stress preceding a more intense stress by the beneficial effect of stress memory. In this work, we tested several thermal stress protocols in oilseed rape differing in intensity, period of exposure, duration and frequency under controlled conditions, with the aim of characterising the plant responses to repeated stresses during the crop cycle (intragenerational effects) and over two generations of stressed plants (intergenerational effects). Our ecophysiological characterisation works show that the effects of repeated heat stresses are not significant on total yield due to compensation phenomena reflecting the plasticity of the oilseed rape, in contrast to the effects on seed quality criteria. These effects decrease the fatty acid content, modify the proportion of monounsaturated fatty acids at the expense of polyunsaturated fatty acids (i.e. increase in the ω6:ω3 ratio) and lead to a degradation of the physiological quality of the seeds (i.e. loss of membrane integrity, acceleration of germination and increase of dormancy). Our results also indicated that a moderate stress preceding a more intense late stress had a beneficial effect only on seed nitrogen content and a ratio of oligosaccharides of the raffinose family, which is an indicator of seed desiccation tolerance. With the aim of improving crop performances in the context of climate change, thermopriming protocols could be proposed to targeted major seed quality compounds. Therefore, these protocols must consider (i) the optimal temperature for the compound synthesis process and (ii) the synchronisation between the thermal event which is expected to have a priming effect and the synthesis/maturation period of the targeted compound. In parallel to this ecophysiological characterisation, we tested three modelling approaches (i.e. ecoclimatic indicators, a (semi-) mechanistic crop model and two data mining methods) which highlighted (i) the non-additive effects of repeated thermal stresses and (ii) the need to improve the temperature functions within mechanistic crop models. Our modelling study is a proof of concept of the need to consider stress memory in predictive crop models, which demonstrates the need to implement the current models in order to better estimate the effects of repeated thermal stresses and their consequences on the yield and quality of harvested products.De nombreuses études font le constat des effets délétères du stress thermique pendant la phase reproductrice des végétaux, ce qui est préjudiciable au rendement et à la qualité des produits récoltés chez les espèces de grandes cultures. Cependant, dans un contexte de changement climatique caractérisé par une fréquence accrue des vagues de chaleur printanières et estivales, la réponse des cultures à la répétition des stress thermiques reste encore peu étudiée et leur interprétation ne prend pas souvent en compte la possibilité d’un effet mémoire du stress modifiant la réponse des cultures à des stress ultérieurs. Cet effet mémoire peut être bénéfique grâce à un effet priming atténuant ou négatif par un effet amplificateur des stress successifs. En effet, il a été démontré qu’il était possible de sensibiliser les plantes grâce à une période de stress modéré précédant un stress plus intense par l’effet bénéfique de la mémoire du stress. Dans le cadre de cette thèse, nous avons testé plusieurs protocoles des stress thermiques chez le colza, différant par leur intensité, la période d’exposition, la durée et la fréquence en conditions contrôlées, dans l’objectif de caractériser les réponses des plantes aux stress répétés pendant le cycle de la culture (effets intragénérationnels) et au cours de deux générations de plantes stressées (effets intergénérationnels). Nos travaux de caractérisation écophysiologique montrent que les effets des stress thermiques répétés ne sont pas significatifs sur le rendement total du fait des phénomènes de compensation reflétant la plasticité du colza, à la différence des effets sur les critères de qualité grainière. Ces effets diminuent la teneur en acides gras, modifient les proportion d’acides gras monoinsaturés au détriment des acides gras polyinsaturés (i.e. augmentation du ratio ω6:ω3) et conduisent à une dégradation de la qualité physiologique des graines (i.e. perte de l'intégrité membranaire, accélération de la germination et augmentation de la dormance). Nos résultats ont également indiqué qu’un stress modéré précédant un stress tardif plus intense avait un effet bénéfique, mais uniquement sur la teneur en azote des graines et un ratio d’oligosaccharides de la famille du raffinose, indicateur de la tolérance à la dessiccation. Dans des perspectives d’amélioration des performances des cultures face au changement climatique, des protocoles thermo-sensibilisants pourraient être proposés en ciblant des composés majeurs de la qualité grainière. Ainsi, les protocoles thermo-sensibilisants envisageables doivent prendre en compte (i) la température optimale au processus de synthèse du composé ; et (ii) la synchronisation entre l’événement thermique ayant un effet bénéfique et la période de synthèse/maturation du composé ciblé. En parallèle à ce travail de caractérisation écophysiologique, nous avons testé trois approches de modélisation (i.e. indicateurs écoclimatiques, un modèle de culture (semi-) mécaniste et deux méthodes de fouille de données) qui ont mis en évidence (i) les effets non additifs des stress thermiques répétés et (ii) la nécessité d’améliorer les fonctions de température au sein des modèles de culture mécanistes. Notre travail de modélisation est une preuve de concept sur la nécessité de considérer la mémoire du stress dans les modèles prédictifs des performances culturales, qui démontre le besoin de faire évoluer les modèles actuels pour mieux estimer les effets des stress thermiques répétés et leurs conséquences sur le rendement et la qualité des produits récoltés

Modelling Memory: do crop models need to become nostalgic?

International audienceIncreased frequency of stress events such as heat waves has been observed for the last decades. Based on the last IPCC report, they are expected to be more frequent, to last longer and to increase in intensity during the reproductive phase of economically important crops. Many recent studies pointed out induced memory effects of stressing events when plants are challenged several times with similar stresses throughout the crop season. These memory effects were shown to be potentially beneficial since the plants are 'primed' and thus more prepared to develop an earlier, more rapid, intense and/or sensitive response when the stress recurs [1]. Therefore, the new climatic patterns prompts to take into account stress memory into predictive crop modelling approaches so as to estimate the effects of repeated stresses and their consequences on crop yield, quality of harvested products. During the last decades, the use of crop models have been enlarged to climate change driven predictions [2]. While evidence for improving crop climate models and especially the temperature response functions in order to reduce uncertainty in yield simulations before any decision making in agriculture, no modelling studies have attempted to decipher and interpret simulation bias in the light of stress memory nor they focused on methodologies to take into account stress memory effects

Modelling Memory: do crop models need to become nostalgic?

International audienceIncreased frequency of stress events such as heat waves has been observed for the last decades. Based on the last IPCC report, they are expected to be more frequent, to last longer and to increase in intensity during the reproductive phase of economically important crops. Many recent studies pointed out induced memory effects of stressing events when plants are challenged several times with similar stresses throughout the crop season. These memory effects were shown to be potentially beneficial since the plants are 'primed' and thus more prepared to develop an earlier, more rapid, intense and/or sensitive response when the stress recurs [1]. Therefore, the new climatic patterns prompts to take into account stress memory into predictive crop modelling approaches so as to estimate the effects of repeated stresses and their consequences on crop yield, quality of harvested products. During the last decades, the use of crop models have been enlarged to climate change driven predictions [2]. While evidence for improving crop climate models and especially the temperature response functions in order to reduce uncertainty in yield simulations before any decision making in agriculture, no modelling studies have attempted to decipher and interpret simulation bias in the light of stress memory nor they focused on methodologies to take into account stress memory effects

To what extent can ecoclimatic indicators assist crop performance predictions in oilseed rape upon repeated heat stresses?

International audienceModelling is an obligate approach to predict crop yield under a wide range of environmental conditions. The present work aims to improve predictions of crop performance under repeated high temperature events by (i) demonstrating that ecoclimatic indicators (i.e. calculated for a given phenological stage) allow a finer description of the plant critical stages, and (ii) highlighting the non-additive effects of these successive stressful events. For this purpose, statistical models based on large datasets in oilseed rape were developed to look for correlations between ecoclimatic indicators and the plant performance-related variables (i.e. seed yield, lipid and protein content), as follows: (i) the plant cycle was divided into four intervals after flowering, according to the physi-ological stages of development in oilseed rape; (ii) the number of warm days (i.e. above 25 ???C and 30 ???C, respectively) in each interval for 26 combinations of location x year in France was scored; (iii) several statistical models that differed from the combination of ecoclimatic indicators were evaluated; and (iv) the best fit model for each plant performance-related variable was selected following a stepwise approach based on the Akaike Information Criterion. The results highlighted that contrasting final crop performances were tightly related to the timing, frequency and intensity of high temperature events after flowering. In addition, specific combinations of these ecoclimatic indicators were much more predictive of the crop performance-related variables than a single cumulative indicator which reflects the sum of all stresses in the same period. These results support our prior assumption that the outcome of several successive stressful events is not equal to the sum of each individual effect. The proposed approach is a proof of concept of the need to consider stress memory (i.e. the capacity of plants to store and retrieve information acquired during an initial exposure to stress) in predictive crop models, so as to better estimate the effects of repeated stresses and their consequences on crop yield and quality of harvested products

Towards a better characterization of heat stress recurrence: a case study in oilseed rape

International audienc

Towards a better characterization of heat stress recurrence: a case study in oilseed rape

International audienc