Speciation Success of Polyploid Plants Closely Relates to the Regulation of Meiotic Recombination

Polyploidization is a widespread phenomenon, especially in flowering plants that have all undergone at least one event of whole genome duplication during their evolutionary history. Consequently, a large range of plants, including many of the world’s crops, combines more than two sets of chromosomes originating from the same (autopolyploids) or related species (allopolyploids). Depending on the polyploid formation pathway, different patterns of recombination will be promoted, conditioning the level of heterozygosity. A polyploid population harboring a high level of heterozygosity will produce more genetically diverse progenies. Some of these individuals may show a better adaptability to different ecological niches, increasing their chance for successful establishment through natural selection. Another condition for young polyploids to survive corresponds to the formation of well-balanced gametes, assuring a sufficient level of fertility. In this review, we discuss the consequences of polyploid formation pathways, meiotic behavior and recombination regulation on the speciation success and maintenance of polyploid species

Genetic diversity in Mediterranean Brassica vegetables: seed phenotyping could be useful for sustainable crop production

The European BrasExplor project aims to explore the genetic diversity present in two economically important Brassica crop species, Brassica oleracea and B. rapa, for sustainable crop production. This diversity is present in wild populations but also in cultivated landraces and has been shaped by contrasting environments. An international consortium of 11 partners has begun to collect and multiply wild populations extending from the French North Atlantic coast to the southern Algerian desert as well as local cultivars from 6 contributing countries in order to characterize the genetic diversity available over a wide soil-climate gradient. A total of 100 populations has been obtained for each species. Identifying the genetic variation and understanding the basis for it will allow the development of breeding strategies for a better adaptation of turnip (Brassica rapa) and cabbage (Brassica oleracea var. capitata) to climate change. One third of the collection has been already phenotyped for its germination traits of native seeds harvested in 2020 for wild populations or of local landraces provided by farmers and seed banks. In favourable conditions, a high diversity in germination capacity and germination rate was observed independently of seed age. The two species have a different germination profile: some turnip seeds can stand higher temperature and lower water potential than most cabbage seeds. Variation in flowering time has also been documented in these plants.We are grateful to Benjamin Foltran for his contribution to the project during his internship, Anne-Sophie Grenier for her input in communication and project website. We also thank Hakima Arrar, Fariza Boussad, Thouraya Rhim, Ilahy Riadh who are involved in field phenotyping. BrasExplor project is funded by the PRIMA programme supported under Horizon ? ? ? ? the European Union’s framework programme for research and innovation.Peer reviewe

Scientists’ Warning to Humanity: Rapid degradation of the world\u27s large lakes

Large lakes of the world are habitats for diverse species, including endemic taxa, and are valuable resources that provide humanity with many ecosystem services. They are also sentinels of global and local change, and recent studies in limnology and paleolimnology have demonstrated disturbing evidence of their collective degradation in terms of depletion of resources (water and food), rapid warming and loss of ice, destruction of habitats and ecosystems, loss of species, and accelerating pollution. Large lakes are particularly exposed to anthropogenic and climatic stressors. The Second Warning to Humanity provides a framework to assess the dangers now threatening the world\u27s large lake ecosystems and to evaluate pathways of sustainable development that are more respectful of their ongoing provision of services. Here we review current and emerging threats to the large lakes of the world, including iconic examples of lake management failures and successes, from which we identify priorities and approaches for future conservation efforts. The review underscores the extent of lake resource degradation, which is a result of cumulative perturbation through time by long-term human impacts combined with other emerging stressors. Decades of degradation of large lakes have resulted in major challenges for restoration and management and a legacy of ecological and economic costs for future generations. Large lakes will require more intense conservation efforts in a warmer, increasingly populated world to achieve sustainable, high-quality waters. This Warning to Humanity is also an opportunity to highlight the value of a long-term lake observatory network to monitor and report on environmental changes in large lake ecosystems

Stable epidemic control in crops based on evolutionary principles: Adjusting the metapopulation concept to agro-ecosystems

In agro-ecosystems, epidemics reduce crop yield. Disease development depends on interactions in time and space between host plants, pathogens, the environment and humans. There is an urgent need to reconsider disease control tactics by linking ecological and evolutionary concepts at the landscape scale, as achieved for natural ecosystems. The aim of our work is to adjust the geographic mosaic of coevolution theory between hosts and pathogens to agro-ecosystems. In agro-ecosystems, adaptation dynamics at the landscape scale depend jointly on annual epidemics, the flow between demes, and human actions, which exacerbate homogeneities in time and space. We describe a framework to take into account these direct and indirect human actions on host agro-metapopulations, which influence the size and composition of pathogen agro-metapopulation demes. By linking disciplinary concepts it becomes possible to optimize the stabilization of disease control efficacy by designing management strategies to selectively apply evolutionary costs. At present, the pathogen agro-metapopulation adapts to its host and the other way around does not occur. However, these evolutionary costs can be used to maintain the pathogen agro-metapopulation locally non-adapted to the host agro-metapopulation. The use of this framework will allow crop protection approaches to be redesigned by modifying the host agro-metapopulation dynamics depending on the observed state of the pathogen agro-metapopulation. (C) 2012 Elsevier B.V. All rights. reserved

Optimization of Recombination in Interspecific Hybrids to Introduce New Genetic Diversity into Oilseed Rape (Brassica napus L.)

International audienceBrassica napus (oilseed rape, rapeseed, canola) is an agriculturally important allotetraploid (2n = AACC) species in the Brassica genus. However, due to its recent origin from only a few hybridization events between progenitor diploid species B. rapa (2n = AA) and B. oleracea (2n = CC), and due to stringent breeding selection pressure for oil-quality traits, B. napus has very narrow genetic diversity. This creates a problem for breeders, who need genetic diversity for continual improvement of agronomic traits. Innovative strategies can be proposed using homologous recombination to generate more stable material from crosses with progenitor species B. rapa and B. oleracea as well as related allopolyploids B. juncea (2n = AABB) and B. carinata (2n = BBCC), as all share a genome or subgenome (set of chromosomes) in common with B. napus. These methods are useful for trait introgression into B. napus, whatever their genetic control, as higher recombination frequencies allow a smaller genomic region to be introgressed with less chance of linkage drag. However, useful traits can be also transferred via homeologous pairing (between chromosomes from different genomes) in interspecific hybrids between B. napus and close relatives. This method is difficult and generally results in large genomic introgression regions, with an increased chance of linkage drag (co-introgression of genes with a negative effect on yield traits), but is relevant for traits under monogenic control. The advantages and limitations of each strategy according to the ploidy level of the hybrids are presented

La domestication, un frein à l'invasion ?

National audienc

Consequences of gene flow between oilseed rape and wild radish

International audienceGene flow and introgression from crops to wild species can modify the adaptive potential and weediness of arable-land plant species. It gained recent importance with the release of genetically modified (GM) crops because of the risk of transfer of herbicide-resistance genes to related weeds. It is also a permanent possibility that could have occurred in the past with any conventional variety. In order to investigate this “normal” phenomenon and its impact, we developed three approaches in the framework of the study of gene flow between oilseed rape (Brassica napus) and wild radish (Raphanus raphanistrum). First, we compared the growth and reproduction of progeny of advanced backcross generations of interspecific hybrids (stabilized BC9 at 2n=18 chromosomes) displaying various levels of molecular markers of the crop parent. Lower fitness accompanies the presence of introgression. Second, we compared morphology and growth of weedy populations of wild radish belonging to regions where the crop was present or absent for long time. Evidence for neutral introgression in wild radish is presented. Third, we developed a simulation model to predict the fate of an advantageous transgene in a population of wild radish following hybridization with a GM crop. We present the generic model structure, comprising stage-structure (from F1 to BC2), spatial realism (i.e. including field borders and waste places) and stochasticity. By focusing on the most influencing parameters, we show that the large uncertainty on input parameters led to unpredictability for the fate of the transgene in the wild radish population