Environmental variation and geographic distribution of the Brachypodium distachyon grass complex species’ in Tunisia.

The Brachypodium genus contains the model grasses B. distachyon, B. stacei and B. hybridum, that are useful for molecular and physiological studies relevant to grain, pasture and bioenergy crops, as well as ecology. In this paper, we analyze the natural variation in climate/geographical diversity that exists within these species in the Tunisian territory. To capture the genetic diversity within this species complex in relation to their geographic distribution in Tunisia, 360 of Brachypodium accessions from the Tunisian territory were collected and genotyped by ALB165 marker. Overall, 314 samples were classified into hybridum and the rest as diploid for one of the two progenitor’s species (B. distachyon and B. stacei). Environmental niche analysis indicated that, generally, B. distachyon grows in higher, cooler, and wetter places north of 36°; B. stacei in lower, warmer, and drier places; nd B. hybridum in places with intermediate ecological features and across latitudinal boundaries but also overlapping with those of its parents, more often with those of B. stacei

Insertion/Deletion markers for assessing the genetic variation and the spatial genetic structure of Tunisian Brachypodium hybridum populations

The wild annual grass Brachypodium hybridum, an allotetraploid species derived from the natural hybridization between the diploid species B. distachyon (2n=10) and B. stacei (2n=20). This trio of species has been suggested as a model system for polyploidy. Brachypodium hybridum is the most widespread Brachypodium species in Tunisia. Natural diversity can be used as a powerful tool to uncover gene function and, in the case of B. hybridum, to understand the functional consequences of polyploidy. Here, we examined the spatial distribution of genetic variation of B. hybridum across its entire range in Tunisia and tested underlying factors that shaped its genetic variation. Population genetic analyses were conducted on 145 individuals from 9 populations using 8 InDel markers. Results indicated a relatively high level of within-population genetic diversity (He = 0.35) and limited among-population differentiation (FPT = 0.20) for this predominantly self-pollinating grass. UPGMA cluster analyses, PCoA and Bayesian clustering supported the demarcation of the populations into 3 groups that were not correlated with location or altitude, suggesting a loose genetic affinity of B. hybridum populations in relation to their geographical locations, and no obvious genetic structure among populations across the study area. This pattern was associated with a considerable amount of an asymmetric gene flow between populations. Overall, the obtained results suggest that the long-distance seed-dispersal is the most important factor in shaping the spatial genetic structure of B. hybridum in Tunisia. They also provide key guidelines for on-going and future work including breeding programs and genome-wide association studies

Abiotic Stress Response in <em>Brachypodium</em>

Understanding the mechanisms of physiological response in plants is crucial to building sustainable agriculture, especially under the current worldwide climate and environmental crises. Thus, plants that successfully acclimate to stress can decrease growth under stressful conditions. Brachypodium, an undomesticated grass species with close evolutionary relationships to wheat and barley, is a promising model organism of crop research. It can grow under various conditions and possess specific adaptations or tolerance mechanisms. Hence, it promises to greatly accelerate the process of gene discovery in the grasses and to serve as bridges in the exploration of panicoid and pooid grasses, arguably two of the most important clades of plants from a food security perspective. Brachypodium could hence efficaciously acclimate to the drought, salinity, cold, heat, and nutrient stress variations by reversible hypo (hyper)-activation of specific genes or sustaining transcription states as well as by reducing growth and osmotic adjustment. Nonetheless, B. stacei and B. hybridum have more plasticity and more adaptiveness than B. distachyon to abiotic stress. This review will describe advancements in knowledge of the physiological and metabolic adjustments that are needed for abiotic stress tolerance

Environmental variation and geographic distribution of the Brachypodium distachyon grass complex species’ in Tunisia.

The Brachypodium genus contains the model grasses B. distachyon, B. stacei and B. hybridum, that are useful for molecular and physiological studies relevant to grain, pasture and bioenergy crops, as well as ecology. In this paper, we analyze the natural variation in climate/geographical diversity that exists within these species in the Tunisian territory. To capture the genetic diversity within this species complex in relation to their geographic distribution in Tunisia, 360 of Brachypodium accessions from the Tunisian territory were collected and genotyped by ALB165 marker. Overall, 314 samples were classified into hybridum and the rest as diploid for one of the two progenitor’s species (B. distachyon and B. stacei). Environmental niche analysis indicated that, generally, B. distachyon grows in higher, cooler, and wetter places north of 36°; B. stacei in lower, warmer, and drier places; nd B. hybridum in places with intermediate ecological features and across latitudinal boundaries but also overlapping with those of its parents, more often with those of B. stacei

Morphological evaluation of cork oak (Quercus suber): Mediterranean provenance variability in Tunisia

Twenty-six provenances (2 340 plants) of cork oak (Quercus suber spp.) originating from Portugal, Spain, Italy, Morocco, Algeria, and Tunisia were tested for genetic variation among and within provenances by growth traits. Seven morphometrical characters were measured in 90 plants from each provenance. Analysis of variance showed highly significant differences for all characters. The phenotypic coefficient of differentiation reached 0.24 for the form and 0.22 for height, thus revealing a strong structuring between the provenances. Comparative study of growth among the provenances revealed more vigorous growth and better survival rate for those from Morocco, Spain, and Portugal, which may constitute better materials for afforestation. Furthermore, this variability appeared to be geographically structured and would be mainly genetically controlled, as cork oak provenances were cultivated under the same environmental conditions. Our results should be helpful for guide forest managers in afforestation.Évaluation morphologique chez le chêne liège (Quercus suber) : variabilité des provenances méditerranéennes en Tunisie. La variabilité génétique inter et intra-provenances a été étudiée pour des caractères de croissance chez Quercus suber spp. 26 provenances (2 340 individus) de chêne liège originaires d'Espagne, du Portugal, d'Italie, du Maroc, d'Algérie et de la Tunisie ont été implantées et testées. Sept caractères morphométriques, jugés discriminants, ont été mesurés chez 90 individus par provenance. L'analyse statistique des résultats a montré des différences hautement significatives entre ces provenances. Le plus haut coefficient de différentiation Qst est trouvé pour les caractères forme (0,24 %) et hauteur (0,22 %). L'étude comparative a en outre révélé une croissance plus vigoureuse associée à une moindre mortalité chez les provenances originaires du Portugal, d'Espagne et du Maroc, leur conférant ainsi un intérêt potentiel pour le reboisement. La variabilité observée chez le chêne liège apparaît structurée selon l'origine géographique et serait essentiellement de nature génétique, puisque toutes les provenances ont été cultivées dans les mêmes conditions pédoclimatiques

Genetic variability of morpho-physiological response to phosphorus deficiency in Tunisian populations of Brachypodium hybridum

Brachypodium hybridum (Poaceae) is widely distributed in the dry environments in Mediterranean basin, due to its high tolerance to drought. Investigating the natural variation of B. hybridum in response to environmental stresses is crucial for unraveling the genetic network of its stress tolerance. 79 B. hybridum lines from eight Tunisian populations were screened for their performance to low P availability using morpho-physiological parameters. ANOVA showed that treatment and population*treatment factors were the most contributors in the explained variance for the majority of parameters. A considerable population differentiation was detected in control and under P level (Qst = 0.77 vs Qst = 0.62). This suggests that B. hybridum exhibit an adaptive differential response to P deficiency related environmental conditions. Results revealed that Raouad and Sejnen lines were the most tolerant to P deficiency followed by Haouaria and Enfidha lines. The remaining populations were classified as sensitive. This pattern suggests that coastal populations were more tolerant to P deficiency than the inland ones. A slightly higher heritability was evidenced under low P level for most of traits, indicating that the direct selection under P deficiency is more reliable than an indirect one under optimal P supply.SCOPUS: ar.jDecretOANoAutActifinfo:eu-repo/semantics/publishe