Contribution à l’étude transcriptomique de la maladie des feuilles cassantes chez le palmier dattier en Tunisie (Phoenix dactylifera L.)

Introduction Le palmier dattier (Phœnix dactylifera L.) est considéré comme étant l’arbre de vie dans les régions sahariennes des pays de l’Afrique du Nord et du Moyen-Orient. En effet, cette plante dioïque et pérenne, constitue l’axe principal de l’agro-système oasien. A ce sujet, le palmier dattier joue un important rôle socioéconomique en Tunisie. En outre, il constitue la base de la production agricole ainsi que la principale source financière et alimentaire des oasiens. Cependant, en dép..

Exploration of bacterial diversity in leaves and rhizosphere soil of flood affected and unaffected apricot trees

International audiencePlants harbor diverse and taxonomically structured communities of protective microorganisms that confer beneficial characteristics in plant growth and protection against biotic and abiotic stresses. The aim of this study is to characterize the composition of endophytic bacterial communities in leaves and rhizobacterial communities of the flood affected and unaffected apricot trees by 16S rRNA genes metabarcoding. Results showed a slight bacterial diversity reduction in flood affected condition compared to the unaffected one. The relative bacterial abundance analysis showed that the bacterial taxa were almost uniformly distributed between the leaves. However, a clear differential taxa abundance was observed in rhizosphere soil which may be associated with apricot tree environmental status. In fact, the flood affected rhizosphere soil showed a significant increase in several bacterial taxa including particularly Bacillusfrigoritolerans and Pseudoarthrobacterphenanthrenivorans which are known to be beneficial to soil. However, some Actinobacteria genera that promote growth of plants, including Nocardioidessp.,Streptomycessp.,BlastococcusandGeodermatophilus were decreased in abundance. This distribution of abundance and diversity of the bacterial community in the flood affected tree can be correlated to abiotic stress. These results provide new insights into rhizosphere-associated microbes that are likely playing a crucial role in plant growth and survival

Evolution of sex chromosomes prior to speciation in the dioecious Phoenix species

International audienceUnderstanding the driving forces and molecular processes underlying dioecy and sex chromosome evolution, leading from hermaphroditism to the occurrence of male and female individuals, is of considerable interest in fundamental and applied research. The genus Phoenix, belonging to the Arecaceae family, consists uniquely of dioecious species. Phylogenetic data suggest that the genus Phoenix has diverged from a hermaphroditic ancestor which is also shared with its closest relatives. We have investigated the cessation of recombination in the sex-determination region within the genus Phoenix as a whole by extending the analysis of P. dactylifera SSR sex-related loci to eight other species within the genus. Phylogenetic analysis of a date palm sex-linked PdMYB1 gene in these species has revealed that sex-linked alleles have not clustered in a species-dependent way but rather in X and Y-allele clusters. Our data show that sex chromosomes evolved from a common autosomal origin before the diversification of the extant dioecious species

Genetic diversity of Southeastern Nigerien date palms reveals a secondary structure within Western populations

International audienceDate palm (Phoenix dactylifera L.) is mainly cultivated for its edible fruit and is of great socio-economic importance for the populations of arid zones. Analysis of the date palm genetic diversity in the Old World had revealed a strong genetic structure with the existence of two gene pools, one Eastern comprising Asia and Djibouti, and one Western, consisting of North African accessions. So far, mainly date palm populations from countries within the Maghreb and the Middle East were characterized, but no information from the Sahel was included. Here, we present the genetic diversity of date palms from Southeastern Niger. The DNA of 113 date palm accessions were analyzed and compared with a database containing the genetic information of 248 accessions from the Old World. The diversity generated from microsatellite markers was compared to that of the same loci of both the Eastern and Western genetic pools. Our results show that date palms from Southeastern Niger constitute a unique group with a high level of genetic diversity. Moreover, even though this group is included in the Western genetic pool, it shows a specific originality which differentiates it from other Western populations. It also shows one of the lowest admixture levels of the Western pool. Global analysis showed a secondary genetic structure within the Western pool highlighting a new genetic group located in Southeastern Niger that distinguishes itself from the North African group

Sur la nécessité de combiner l'ethnobotanique et la génétique pour évaluer l'agrobiodiversité et son évolution des plantes cultivées : Une étude de cas sur les palmiers dattiers (Phoenix dactylifera L.) dans l'oasis de Siwa, Égypte

International audienceCrop diversity is shaped by biological and social processes interacting at different spatiotemporal scales. Here we combined population genetics and ethnobotany to investigate date palm (Phoenix dactylifera L.) diversity in Siwa Oasis, Egypt. Based on interviews with farmers and observation of practices in the field, we collected 149 date palms from Siwa Oasis and 27 uncultivated date palms from abandoned oases in the surrounding desert. Using genotyping data from 18 nuclear and plastid microsatellite loci, we confirmed that some named types each constitute a clonal line, i.e. a true-to-type cultivar. We also found that others are collections of clonal lines, i.e. ethnovarieties, or even unrelated samples, i.e. local categories. This alters current assessments of agrobiodiversity, which are visibly underestimated, and uncovers the impact of low-intensity, but highly effective, farming practices on biodiversity. These hardly observable practices, hypothesized by ethnographic survey and confirmed by genetic analysis, are enabled by the way Isiwans conceive and classify living beings in their oasis, which do not quite match the way biologists do: a classic disparity of etic vs. emic categorizations. In addition, we established that Siwa date palms represent a unique and highly diverse genetic cluster, rather than a subset of North African and Middle Eastern palm diversity. As previously shown, North African date palms display evidence of introgression by the wild relative Phoenix theophrasti Greuter, and we found that the uncultivated date palms from the abandoned oases share even more alleles with this species than cultivated palms in this region. The study of Siwa date palms could hence be a key to the understanding of date palm diversification in North Africa. Integration of ethnography and population genetics promoted the understanding of the interplay between diversity management in the oasis (short-time scale), and the origins and dynamic of diversity through domestication and diversification (long-time scale).La diversité des plantes cultivées est façonnée par des processus biologiques et sociaux qui interagissent à différentes échelles spatiotemporelles. Nous avons ici combiné la génétique des populations et l’ethnobotanique pour étudier la diversité du palmier-dattier (Phoenix dactylifera L.) dans l’oasis de Siwa, en Égypte. Sur la base d’entretiens avec des agriculteurs et de l’observation des pratiques sur le terrain, nous avons collecté 149 palmiers dattiers de l’oasis de Siwa et 27 palmiers dattiers non cultivés provenant d’oasis abandonnées dans le désert environnant. En utilisant les données de génotypage de 18 loci microsatellites nucléaires et plastidiques, nous avons confirmé que certains types nommés constituent chacun une ligne clonale, c’est-à-dire un « cultivar vrai » (true-to-type). Nous avons également constaté que d’autres sont des collections de lignes clonales, c’est-à-dire des « ethnovariétés », voire même des échantillons non apparentés, c’est-à-dire des « catégories locales ». Cela modifie les évaluations existantes de l’agrobiodiversité, qui sont visiblement sous-estimées, et révèle l’impact des pratiques agricoles de faible intensité, mais très efficaces, sur la biodiversité. Ces pratiques difficilement observables, supposées par l’enquête ethnographique et confirmées par l’analyse génétique, sont rendues possibles par la façon dont les Isiwans conçoivent et classifient les êtres vivants dans leur oasis, qui ne correspond pas tout à fait à la façon dont les biologistes le font : une disparité classique des catégorisations étiques vs. émiques. En outre, nous avons établi que les palmiers dattiers de Siwa représentent un groupe génétique unique et très diversifié, plutôt qu’un sous-ensemble de la diversité des palmiers d’Afrique du Nord et du Moyen-Orient. Comme nous l’avons montré précédemment, les palmiers dattiers d’Afrique du Nord présentent des signes d’introgression par le parent sauvage Phoenix theophrasti Greuter, et nous avons constaté que les palmiers dattiers non cultivés des oasis abandonnées partagent encore plus d’allèles avec cette espèce que les palmiers cultivés de cette région. L’étude des palmiers dattiers de Siwa pourrait donc être une clé pour la compréhension de la diversification des palmiers dattiers en Afrique du Nord. L’intégration de l’ethnographie et de la génétique des populations a permis de comprendre l’interaction entre la gestion de la diversité dans l’oasis (l’échelle du court terme) et les origines et la dynamique de la diversité au travers de la domestication et de la diversification (l’échelle du long terme)

Endemic insular and coastal Tunisian date palm genetic diversity

International audienceThe breeding of crop species relies on the valorisation of ancestral or wild varieties to enrich the cultivated germplasm. The Tunisian date palm genetic patrimony is being threatened by diversity loss and global climate change. We have conducted a genetic study to evaluate the potential of spontaneous coastal resources to improve the currently exploited Tunisian date palm genetic pool. Eighteen microsatellite loci of Phoenix dactylifera L. were used to compare the genetic diversity of coastal accessions from Kerkennah, Djerba, GabSs and continental date palm accessions from Tozeur. A collection of 105 date palms from the four regions was analysed. This study has provided us with an extensive understanding of the local genetic diversity and its distribution. The coastal date palm genotypes exhibit a high and specific genetic diversity. These genotypes are certainly an untapped reservoir of agronomically important genes to improve cultivated germplasm in continental date palm

Endemic insular and coastal Tunisian date palm genetic diversity

The breeding of crop species relies on the valorisation of ancestral or wild varieties to enrich the cultivated germplasm. The Tunisian date palm genetic patrimony is being threatened by diversity loss and global climate change. We have conducted a genetic study to evaluate the potential of spontaneous coastal resources to improve the currently exploited Tunisian date palm genetic pool. Eighteen microsatellite loci of Phoenix dactylifera L. were used to compare the genetic diversity of coastal accessions from Kerkennah, Djerba, GabSs and continental date palm accessions from Tozeur. A collection of 105 date palms from the four regions was analysed. This study has provided us with an extensive understanding of the local genetic diversity and its distribution. The coastal date palm genotypes exhibit a high and specific genetic diversity. These genotypes are certainly an untapped reservoir of agronomically important genes to improve cultivated germplasm in continental date palm