Agronomic Value of Mixture of Perennial Rye-Grass Cultivars: Preliminary Results

Mixtures of grass and legume species are commonly used in sown grasslands. Mixtures have been shown to be favourable for stable production over cycles and years due to a succession of species over time (Mosimann & Charles, 1996 ; Nie et al, 2004). However, little is known whether the genetic variation in pure stands has an influence on the agronomic value and its variation over seasons

Performance and quality of tall fescue (Festuca arundinacea Schreb.) and perennial ryegrass (Lolium perenne L.) and mixtures of both species grown with or without white clover (Trifolium repens L.) under cutting management

There is increasing interest in tall fescue (Festuca arundinacea Schreb.) in Western Europe and elsewhere, mainly because of its better drought resistance and yield potential compared with perennial ryegrass (Lolium perenne L.). Important drawbacks of tall fescue, compared with perennial ryegrass, are its lower digestibility and voluntary intake. Mixtures of both species might combine the advantages of each, and species interactions may eventually lead to transgressive overyielding. We compared the agronomic performance of tall fescue, perennial ryegrass and tall fescue-perennial ryegrass mixtures, as pure-grass swards or in association with white clover (Trifolium repens L.). Tall fescue-perennial ryegrass mixtures differed in the proportion and ploidy of the perennial ryegrass component. Yield, feed quality and botanical composition were measured in the 3years after the sowing year. We found significant effects of ploidy of the ryegrass variety and of the proportion of ryegrass in the initial seed mixture on the botanical composition of the swards. Nevertheless, all swards were dominated by tall fescue at the end of the experiment. No overyielding of the mixtures compared with that of single-species swards was found, but feed quality was intermediate between that of the single-species swards. Mixed swards had better drought resistance than L.perenne and higher feeding quality than F.arundinacea swards

Genome-wide genotyping data renew knowledge on genetic diversity of a worldwide alfalfa collection and give insights on genetic control of phenology traits

China’s and Europe’s dependence on imported protein is a threat to the food self-sufficiency of these regions. It could be solved by growing more legumes, including alfalfa that is the highest protein producer under temperate climate. To create productive and high-value varieties, the use of large genetic diversity combined with genomic evaluation could improve current breeding programs. To study alfalfa diversity, we have used a set of 395 alfalfa accessions (i.e. populations), mainly from Europe, North and South America and China, with fall dormancy ranging from 3 to 7 on a scale of 11. Five breeders provided materials (617 accessions) that were compared to the 400 accessions. All accessions were genotyped using Genotyping-by-Sequencing (GBS) to obtain SNP allele frequency. These genomic data were used to describe genetic diversity and identify genetic groups. The accessions were phenotyped for phenology traits (fall dormancy and flowering date) at two locations (Lusignan in France, Novi Sad in Serbia) from 2018 to 2021. The QTL were detected by a Multi-Locus Mixed Model (mlmm). Subsequently, the quality of the genomic prediction for each trait was assessed. Cross-validation was used to assess the quality of prediction by testing GBLUP, Bayesian Ridge Regression (BRR), and Bayesian Lasso methods. A genetic structure with seven groups was found. Most of these groups were related to the geographical origin of the accessions and showed that European and American material is genetically distinct from Chinese material. Several QTL associated with fall dormancy were found and most of these were linked to genes. In our study, the infinitesimal methods showed a higher prediction quality than the Bayesian Lasso, and the genomic prediction achieved high (>0.75) predicting abilities in some cases. Our results are encouraging for alfalfa breeding by showing that it is possible to achieve high genomic prediction quality

High-Throughput Genome-Wide Genotyping To Optimize the Use of Natural Genetic Resources in the Grassland Species Perennial Ryegrass (Lolium perenne L.)

The natural genetic diversity of agricultural species is an essential genetic resource for breeding programs aiming to improve their ecosystem and production services. A large natural ecotype diversity is usually available for most grassland species. This could be used to recombine natural climatic adaptations and agronomic value to create improved populations of grassland species adapted to future regional climates. However describing natural genetic resources can be long and costly. Molecular markers may provide useful information to help this task. This opportunity was investigated for Lolium perenne L., using a set of 385 accessions from the natural diversity of this species collected right across Europe and provided by genebanks of several countries. For each of these populations, genotyping provided the allele frequencies of 189,781 SNP markers. GWAS were implemented for over 30 agronomic and/or putatively adaptive traits recorded in three climatically contrasted locations (France, Belgium, Germany). Significant associations were detected for hundreds of markers despite a strong confounding effect of the genetic background; most of them pertained to phenology traits. It is likely that genetic variability in these traits has had an important contribution to environmental adaptation and ecotype differentiation. Genomic prediction models calibrated using natural diversity were found to be highly effective to describe natural populations for almost all traits as well as commercial synthetic populations for some important traits such as disease resistance, spring growth or phenological traits. These results will certainly be valuable information to help the use of natural genetic resources of other species

Fertility trends by social status

This article discusses how fertility relates to social status with the use of a new dataset, several times larger than the ones used so far. The status-fertility relation is investigated over several centuries, across world regions and by the type of status-measure. The study reveals that as fertility declines, there is a general shift from a positive to a negative or neutral status-fertility relation. Those with high income/wealth or high occupation/social class switch from having relatively many to fewer or the same number of children as others. Education, however, depresses fertility for as long as this relation is observed (from early in the 20th century)

Pour une estimation de la population « sportive »

Surault Pierre. Pour une estimation de la population « sportive ». In: Population, 46ᵉ année, n°1, 1991. pp. 159-164

Les facteurs de différenciation sociale de la mortalité

Factors of Social Differentiation in Mortality Rates Far from narrowing, as could have been expected, the mortality gap connected with social environment has tended to widen fot the past thirty years in industrialized countries. Against a general background of increased life expectancy, differences in working conditions and behaviour (consumption of alcohol, tobacco and food, physical activity...), with behaviour often influenced by working conditions, on the one hand, differences in access to health care, on the other, account for these differentials in mortality and their increase. And yet, their reduction, through an improvement in the situation of the underprivileged, could increase life expectancy in a significant way.Loin de se réduire, comme on aurait pu s'y attendre, les écarts de mortalité suivant le milieu social ont eu tendance à s'accroître depuis une trentaine d'années dans les pays industrialisés. Dans un contexte général d'allongement de l'espérance de vie, les différences de conditions de travail et de comportements (consommation d'alcool, de tabac et alimentaire, activités physiques...), ceux-ci étant souvent liés à celles-là, d'une part, le recours différentiel aux soins, d'autre part, expliquent ces écarts et leur accroissement. Pourtant, leur réduction, par une amélioration de la situation des plus défavorisés, pourrait entraîner une augmentation sensible de l'espérance de vie.Surault Pierre. Les facteurs de différenciation sociale de la mortalité. In: Espace, populations, sociétés, 1984-3. La mortalité adulte dans les pays industrialisés. pp. 131-140

La diffusion du vieillissement dans les campagnes du Poitou-Charentes

Poitou-Charentes is one of the French regions with the highest rise in the average age of the population. The following article is a study of the spreading of this ageing process in rural zones from 1962 to 1982, focusing the analysis on rural districts, that is those consisting exclusively of rural communities, but also taking into account numerous mixed districts where the same process has been at work. This evolution has spread rapidly to a majority of rural districts, while urban and suburban zones are appearing more and more as relatively young enclaves surrounded by ageing zones where the population is decreasing, with the contrastes becoming more clearly marked. The question is asked whether we have to regard as irreversible the sequence of depopulation and rise in the average age which results in nothing less than desertification and will in the short term create problems in maintaining minimal social structures and meeting the needs of the aged population.La région Poitou-Charentes figure parmi les régions les plus vieillies de France. Est ici analysée la diffusion du vieillissement dans les zones rurales de 1962 à 1982, à partir plus particulièrement de l'étude des cantons ruraux, c'est-à-dire ceux constitués uniquement de communes rurales, sans négliger le cas de nombreux cantons mixtes également vieillis. Le vieillissement s'est rapidement étendu à la majorité des cantons ruraux, les zones urbaines et péri-urbaines apparaissant de plus en plus comme des enclaves relativement jeunes environnées de zones vieillissantes et en dépeuplement, avec une accentuation sensible des contrastes. La question se pose de l'irréversibilité ou non de l'enchaînement dépeuplement-vieillissement conduisant à une véritable désertification et posant à court terme le problème du maintien de structures sociales minimales et de la satisfaction des besoins de la population âgée.Surault Pierre. La diffusion du vieillissement dans les campagnes du Poitou-Charentes. In: Norois, n°140, Octobre-Décembre 1988. Populations et sociétés rurales dans l'ouest et le centre-ouest français. Géo-démographie des campagnes. Actes du Colloque de Poitiers (Mars 1988) [En hommage au Professeur Jean Pitié] pp. 443-452

Réflexions sur les perspectives de mortalité

Observations on projections of mortality rates. The rapid increase in life expectancy in recent years has produced optimism among specialists and upward revision of projections. Yet future mortality rates could be significantly affected by a certain number of risk factors relating in particular to the younger generations and increasing among other things stress-producing situations; in the same way drastic changes in family lifestyle are bringing about an increase in cases of breakdown affecting social segments which are characterized by higher mortality rates. For this reason the increase in average life expectancy is perhaps not inevitable even if the great risk undoubtedly lies more in the widening gap in the mortality rates in relation with the polarisation of society.L'accroissement rapide de l'espérance de vie ces dernières années a provoqué l'optimisme des spécialistes et une révision en hausse des perspectives. Pourtant le niveau futur de la mortalité pourrait être sensiblement affecté par un certain nombre de facteurs de risque touchant en particulier les jeunes générations et accroissant notamment les occasions de stress, de même, les profondes transformations en cours des pratiques familiales provoquent un accroissement des situations de rupture et de la part des catégories de population qui se caractérisent par une surmortalité. C'est pourquoi l'augmentation de la vie moyenne n'est peut-être pas inéluctable même si le risque majeur réside sans doute davantage dans un accroissement des écarts sociaux de mortalité en relation avec la dualisation de la société.Surault Pierre. Réflexions sur les perspectives de mortalité. In: Espace, populations, sociétés, 1986-2. Visages de la population de la France - Faces of french population [Changements démographiques et géographiques de la population de la France. Poitiers novembre 1985.] pp. 85-93

Suicide : silence et idées reçues

Surault Pierre. Suicide : silence et idées reçues. In: Espace, populations, sociétés, 1993-1. Mélanges - Miscellanies. pp. 101-103