The Concepts of Seed Germination Rate and Germinability: A Re-Evaluation for Cool-Season Grasses

Temperature is one the most influential environmental factors for the germination and establishment of grass species. The specific objective of this study was to determine the effects of low constant temperature on the time needed to express the full germination capacity of nondormant seedlots. Fifteen accessions, comprising seven of Lolium perenne L., three of Festuca arundinacea Schreb., three of Dactylis glomerata L. and two of Triticum aestivum L., were evaluated at constant temperatures of 5 and 21 °C. As expected, the germination rates were faster at 21 °C than at 5 °C. Indeed, at 5 °C seeds needed up to twenty-one times longer to reach the maximum germination than when tested at 21 °C. The genotypic variability found for the ratio of germination rates between the two temperatures (i.e., germination rate at 5 °C/germination rate at 21 °C) was much more variable than what is found in the literature for perennial cool-season grasses. On the other hand, in most cases, no significant differences were observed in the germinability (the capacity to germinate) response to 5 °C and 21 °C. Within the four species, twelve of the fifteen studied accessions expressed the same germinability at 5 °C and 21 °C, when given enough time. Only three accessions had final germination percentages higher at 21 °C than at 5 °C. Our results suggest that, in general, nondormant seeds at low temperatures germinate as well as nondormant seeds at near-optimal temperatures, provided they have enough time to express their germination capacity. These findings cast doubts on the validity of conclusions drawn in many studies where germination experiments were performed for a period insufficient to obtain full germination at low temperatures. Another major finding in this work concerns the risk of wrongly estimating germinability at low temperatures

Analysis of the genetic diversity of the germinative response to temperature of populations of Lolium perenne L., Festuca arundinacea Schreb and Dactylis glomerata L.

La germination des graines est une étape importante dans le cycle biologique de la plante, car elle affecte le développement, la survie et la dynamique des populations de semis. La germination commence par l'absorption de l'eau par la graine et se termine par l'allongement de l'axe embryonnaire en dehors du tégument.Elle est influencée par des facteurs environnementaux et le patrimoine génétique de la graine. La température est l'une des factures les plus importants, car elle régule la germination de trois façons: en déterminant la capacité germinative et la vitesse de germination, en enlevant la dormance primaire et/ou secondaire, et en induisant la dormance secondaire.L'objectif de ce travail est d'analyse de la diversité génétique de la réponse germinative à la température de populations de Lolium perenne L., Festuca arundincea Schreb et Dactylis glomerata L.Dans cette étude, nous avons distingué différents types de réponses à la température, ce qui indique que de la diversité génétique existe entre les lots de chaque espèce. Ces différences dans les réponses, aux températures constantes entre 5 et 32 °C, ont été observées au niveau du pourcentage de germination maximale, de la vitesse de germination (α), lu temps de début de germination (tc) et du temps nécessaire pour attendre 95 % de germination finale (t95%). Des sélections divergentes ont été réalisées sur la capacité à germer à des températures non optimales chez des populations de Lolium perenne L. Sur une population issue de la région de Reims, il ressort un effet important de la sélection pour la capacité à germer à 10 °C qui pourrait être expliqué par la présence d'un gène majeur dominant de dormance des graines à faible température, en ségrégation au sein de la population.La comparaison des fréquences alléliques pour de nombreux marqueurs répartis sur le génome entre les individus germant et ceux ne germant pas à différentes températures a permis d'identifier de nombreux gènes potentiellement impliqués dans la capacité des individus à germer à ces températures. L'effet de ces gènes reste à être validé, par exemple par des études d'expression ou par l'étude de populations crées par sélection pour porter des allèles contrastés.Seed germination is an important step in the plant's life cycle, affecting the development, survival and dynamics of seedling populations. Germination begins with the absorption of water by the seed and ends with the elongation of the embryonic axis outside the integument.It is influenced by environmental factors and the genetic heritage of the seed. Temperature is one of the most important factors, which regulates germination in three ways: by determining germination capacity and germination rate, by removing primary and/or secondary dormancy, and by inducing secondary dormancy.The objective of this work is to analyze the genetic diversity of the germinative response to temperature of populations of Lolium perenne L, Festuca arundinacea Schreb, and Dactylis glomerata L.In this study, we distinguished different types of temperature responses, indicating that genetic diversity exists between lots of each species. In this study, we distinguished different types of responses to temperature, indicating that genetic diversity exists between lots of each species. These differences in responses, at constant temperatures between 5 and 32°C, were observed in terms of maximum germination percentage, germination rate (α), germination start time (tc) and time required to reach 95 % of final germination (t95%).Divergent selections were made on the capacity to germinate at sub-optimal temperatures in populations of Lolium perenne L. In a population from the Reims region, there is an important effect of selection for the capacity to germinate at 10 °C, which could be explained by the presence of a major dominant gene for seed dormancy at low-temperature, in segregated within the population. The comparison of allelic frequencies for many markers distributed over the genome between individuals germinating and those not germinating at different temperatures has identified many genes potentially involved in the ability of individuals to germinate at these temperatures. The effect of these genes has yet to be validated, for example by expression studies or by the study of populations created by selection to carry contrasting alleles

Analyse de la diversité génétique de la réponse germinative à la température de populations de Lolium perenne L., Festuca arundinacea Schreb et Dactylis glomerata L.

Seed germination is an important step in the plant's life cycle, affecting the development, survival and dynamics of seedling populations. Germination begins with the absorption of water by the seed and ends with the elongation of the embryonic axis outside the integument.It is influenced by environmental factors and the genetic heritage of the seed. Temperature is one of the most important factors, which regulates germination in three ways: by determining germination capacity and germination rate, by removing primary and/or secondary dormancy, and by inducing secondary dormancy.The objective of this work is to analyze the genetic diversity of the germinative response to temperature of populations of Lolium perenne L, Festuca arundinacea Schreb, and Dactylis glomerata L.In this study, we distinguished different types of temperature responses, indicating that genetic diversity exists between lots of each species. In this study, we distinguished different types of responses to temperature, indicating that genetic diversity exists between lots of each species. These differences in responses, at constant temperatures between 5 and 32°C, were observed in terms of maximum germination percentage, germination rate (α), germination start time (tc) and time required to reach 95 % of final germination (t95%).Divergent selections were made on the capacity to germinate at sub-optimal temperatures in populations of Lolium perenne L. In a population from the Reims region, there is an important effect of selection for the capacity to germinate at 10 °C, which could be explained by the presence of a major dominant gene for seed dormancy at low-temperature, in segregated within the population. The comparison of allelic frequencies for many markers distributed over the genome between individuals germinating and those not germinating at different temperatures has identified many genes potentially involved in the ability of individuals to germinate at these temperatures. The effect of these genes has yet to be validated, for example by expression studies or by the study of populations created by selection to carry contrasting alleles.La germination des graines est une étape importante dans le cycle biologique de la plante, car elle affecte le développement, la survie et la dynamique des populations de semis. La germination commence par l'absorption de l'eau par la graine et se termine par l'allongement de l'axe embryonnaire en dehors du tégument.Elle est influencée par des facteurs environnementaux et le patrimoine génétique de la graine. La température est l'une des factures les plus importants, car elle régule la germination de trois façons: en déterminant la capacité germinative et la vitesse de germination, en enlevant la dormance primaire et/ou secondaire, et en induisant la dormance secondaire.L'objectif de ce travail est d'analyse de la diversité génétique de la réponse germinative à la température de populations de Lolium perenne L., Festuca arundincea Schreb et Dactylis glomerata L.Dans cette étude, nous avons distingué différents types de réponses à la température, ce qui indique que de la diversité génétique existe entre les lots de chaque espèce. Ces différences dans les réponses, aux températures constantes entre 5 et 32 °C, ont été observées au niveau du pourcentage de germination maximale, de la vitesse de germination (α), lu temps de début de germination (tc) et du temps nécessaire pour attendre 95 % de germination finale (t95%). Des sélections divergentes ont été réalisées sur la capacité à germer à des températures non optimales chez des populations de Lolium perenne L. Sur une population issue de la région de Reims, il ressort un effet important de la sélection pour la capacité à germer à 10 °C qui pourrait être expliqué par la présence d'un gène majeur dominant de dormance des graines à faible température, en ségrégation au sein de la population.La comparaison des fréquences alléliques pour de nombreux marqueurs répartis sur le génome entre les individus germant et ceux ne germant pas à différentes températures a permis d'identifier de nombreux gènes potentiellement impliqués dans la capacité des individus à germer à ces températures. L'effet de ces gènes reste à être validé, par exemple par des études d'expression ou par l'étude de populations crées par sélection pour porter des allèles contrastés

The Concepts of Seed Germination Rate and Germinability: A Re-Evaluation for Cool-Season Grasses

Temperature is one the most influential environmental factors for the germination and establishment of grass species. The specific objective of this study was to determine the effects of low constant temperature on the time needed to express the full germination capacity of nondormant seedlots. Fifteen accessions, comprising seven of Lolium perenne L., three of Festuca arundinacea Schreb., three of Dactylis glomerata L. and two of Triticum aestivum L., were evaluated at constant temperatures of 5 and 21 °C. As expected, the germination rates were faster at 21 °C than at 5 °C. Indeed, at 5 °C seeds needed up to twenty-one times longer to reach the maximum germination than when tested at 21 °C. The genotypic variability found for the ratio of germination rates between the two temperatures (i.e., germination rate at 5 °C/germination rate at 21 °C) was much more variable than what is found in the literature for perennial cool-season grasses. On the other hand, in most cases, no significant differences were observed in the germinability (the capacity to germinate) response to 5 °C and 21 °C. Within the four species, twelve of the fifteen studied accessions expressed the same germinability at 5 °C and 21 °C, when given enough time. Only three accessions had final germination percentages higher at 21 °C than at 5 °C. Our results suggest that, in general, nondormant seeds at low temperatures germinate as well as nondormant seeds at near-optimal temperatures, provided they have enough time to express their germination capacity. These findings cast doubts on the validity of conclusions drawn in many studies where germination experiments were performed for a period insufficient to obtain full germination at low temperatures. Another major finding in this work concerns the risk of wrongly estimating germinability at low temperatures

Latest public research on forage and turf and update on CLIMAGIE

National audienc

Latest public research on forage and turf and update on CLIMAGIE

National audienc

SARS-CoV-2 vaccination modelling for safe surgery to save lives: data from an international prospective cohort study

Background: Preoperative SARS-CoV-2 vaccination could support safer elective surgery. Vaccine numbers are limited so this study aimed to inform their prioritization by modelling. Methods: The primary outcome was the number needed to vaccinate (NNV) to prevent one COVID-19-related death in 1 year. NNVs were based on postoperative SARS-CoV-2 rates and mortality in an international cohort study (surgical patients), and community SARS-CoV-2 incidence and case fatality data (general population). NNV estimates were stratified by age (18-49, 50-69, 70 or more years) and type of surgery. Best- and worst-case scenarios were used to describe uncertainty. Results: NNVs were more favourable in surgical patients than the general population. The most favourable NNVs were in patients aged 70 years or more needing cancer surgery (351; best case 196, worst case 816) or non-cancer surgery (733; best case 407, worst case 1664). Both exceeded the NNV in the general population (1840; best case 1196, worst case 3066). NNVs for surgical patients remained favourable at a range of SARS-CoV-2 incidence rates in sensitivity analysis modelling. Globally, prioritizing preoperative vaccination of patients needing elective surgery ahead of the general population could prevent an additional 58 687 (best case 115 007, worst case 20 177) COVID-19-related deaths in 1 year. Conclusion: As global roll out of SARS-CoV-2 vaccination proceeds, patients needing elective surgery should be prioritized ahead of the general population