Search

Design and assessment of innovative Mediterranean vegetable cropping systems to manage root-knot nematodes. Description of the subject. A system approach based on co-design and experimental field evaluation of cropping systems (CSs), combining technical and varietal innovations, has been implemented for sustainable management of root-knot nematodes (RKN) in Mediterranean sheltered vegetable systems. Objectives. Cropping systems combining genetic resistance and cultural practices (crop rotations including susceptible, resistant, and non-host plants; intercropping management with nematicidal cover crops or soil solarization) were assessed over a period of 4 years (i) to reduce RKN populations and increase the durability of varietal resistances, (ii) to study the impact of these systems on soil ecology (plant-parasitic and free-living nematode communities), and (iii) to evaluate their acceptability by farmers. Method. Three CS prototypes, resulting from a co-design process with research and development stakeholders, were compared with CSs conventionally implemented in the Mediterranean region. The three prototypes were also evaluated using complementary methods: (i) system experiments in three commercial farms in Southern France; (ii) analytical experiments to decipher the mechanisms of action for some [agroecological??] levers; (iii) surveys to evaluate the acceptability of the prototypes by farmers. Results. All three CSs were found to be effective (90% RKN decrease, protection of partially resistant Solanaceae, no negative effect on non-phytoparasitic nematodes) and sustainable, when application conditions and soil biological equilibrium were favorable (global soil nematofauna diversified and abundant). The acceptability of the three systems depended on the type of farm where they were implemented and the attitude of the farmers towards innovation. Conclusions. These three CSs still need to be improved, in terms of their efficiency, in consultation with participating farmers, by introducing new agroecological levers, as well as innovation costs. Future research will also need to open up to a more comprehensive management of soil health.

L’objectif de cette recherche est d’étudier l’emploi de la pause dans la parole des hommes politiques et d’observer si des variations sont notables dans l’utilisation des silences dans le discours de ces derniers. Pour répondre à cet objectif, cette étude se fonde sur les travaux menés par Duez (1999 ; 2003), qui ont révélé que la durée des pauses varie en fonction de la situation de l’homme politique vis-à-vis du pouvoir (dans l’opposition vs. au pouvoir) et par rapport aux thèmes abordés durant un débat. Afin de poursuivre ces recherches, notre étude vise à vérifier si l’utilisation et les caractéristiques de la pause varient en fonction de la nature du débat. Notre hypothèse est que l’homme politique adapte le rythme de sa parole, et donc les pauses présentes dans ses énoncés, en fonction de son contradicteur et du type de débat. Pour vérifier cette assertion, nous avons fait le choix d’étudier les pauses chez François Hollande, d’abord en situation de débat face à Martine Aubry, durant la primaire socialiste de 2011, puis en situation de discours, lors du discours préélectoral prononcé au Bourget. Ainsi, les deux émissions ont donné lieu à une transcription des propos tenus par François Hollande, puis, après examen de la posture du locuteur, nous avons localisé les pauses et quantifié leur durée à l’aide du logiciel Praat. D’autres paramètres (vitesse d’articulation, nombre de syllabes par groupe rythmique, …), permettant d’observer les variations de rythme, ont également été quantifiés.

Using long-read sequencing, we assembled and unzipped the polyploid genomes of Meloidogyne incognita, M. javanica and M. arenaria, three of the most devastating plant-parasitic nematodes. We found the canonical nematode telomeric repeat to be missing in these and other Meloidogyne genomes. In addition, we find no evidence for the enzyme telomerase or for orthologs of C. elegans telomere-associated proteins, suggesting alternative lengthening of telomeres. Instead, analyzing our assembled genomes, we identify species-specific composite repeats enriched mostly at one extremity of contigs. These repeats are G-rich, oriented, and transcribed, similarly to canonical telomeric repeats. We confirm them as telomeric using fluorescent in situ hybridization. These repeats are mostly found at one single end of chromosomes in these species. The discovery of unusual and specific complex telomeric repeats opens a plethora of perspectives and highlights the evolutionary diversity of telomeres despite their central roles in senescence, aging, and chromosome integrity., (© 2024. The Author(s).)

The soil bacterium Sinorhizobium meliloti can establish a nitrogen-fixing symbiosis with the model legume Medicago truncatula. The rhizobia induce the formation of a specialized root organ called nodule, where they differentiate into bacteroids and reduce atmospheric nitrogen into ammonia. Little is known on the mechanisms involved in nodule senescence onset and in bacteroid survival inside the infected plant cells. Although toxin-antitoxin (TA) systems have been shown to promote intracellular survival within host cells in human pathogenic bacteria, their role in symbiotic bacteria was rarely investigated. S. meliloti encodes several TA systems, mainly of the VapBC family. Here we present the functional characterization, through a multidisciplinary approach, of the VapBC10 TA system of S. meliloti. Following a mapping by overexpression of an RNase in Escherichia coli (MORE) RNA-seq analysis, we demonstrated that the VapC10 toxin is an RNase that cleaves the anticodon loop of two tRNASer. Thereafter, a bioinformatics approach was used to predict VapC10 targets in bacteroids. This analysis suggests that toxin activation triggers a specific proteome reprogramming that could limit nitrogen fixation capability and viability of bacteroids. Accordingly, a vapC10 mutant induces a delayed senescence in nodules, associated to an enhanced bacteroid survival. VapBC10 TA system could contribute to S. meliloti adaptation to symbiotic lifestyle, in response to plant nitrogen status., (© The Author(s) 2024. Published by Oxford University Press on behalf of the International Society for Microbial Ecology.)