Morphological and physiological behaviour of sea barley (Hordeum marinum ssp marinum) genotypes originating from Soliman Sebkha under increasing salinity

Evaluation of germplasm in salt stress environment may help identifying salt-tolerant genotypes. In this study, we analyzed the genetic diversity of Hordeum marinum, genotypes originated from Soliman Sebkha in response to salinity (0, 250 and 400 mM) by measuring a set of parameters related to growth, water statue and photosynthetic activity. Results of ANOVA showed that variability of measured parameters was explained by the effects genotypes, treatment and their interaction, with treatment factor recorded the highest values. Salinity significantly reduced the photosynthetic rate and related parameters, including stomatal conductance (gs), intercellular CO2 concentration (Ci), and transpiration (E). Several indices for salt tolerance indices comprising tolerance index (TOL), stress tolerance index (STI) and Salt Tolerance (ST) were calculated based on drought biomass (ADW) under non-stressed and under stress conditions. Results showed that lower values of TOL and higher values of ST and STI indicate the superiority of the genotypes having enough plasticity to respond to extreme conditions. Principal Component Analysis clustered genotypes into sensitive (21.43%), moderately tolerant (50%), and highly tolerant (28.57%) groups, depending on their relative potential to sustain good growth under high salinity. Results indicating sufficient genetic variability for salinity tolerance among the studied genotypes, hence tolerant genotypes can be good candidates in future breeding programs

Agronomic and molecular analyses for the characterisation of accessions in Tunisian olive germplasm collections

In this study, a total of 14 agronomic traits, five AFLP primer combinations and ten SSR loci were used to describe and to classify a group of Tunisian olive genotypes into groups based on molecular profiles and agronomic traits. The analysis of variance of the agronomical data revealed significant differences among accessions for all measured traits. The mean phenotypic dissimilarity (0.34 with a range of 0.08-0.6) was low in comparison to dissimilarity calculated using AFLP (0.50 with a range of 0.16-0.70) and SSR markers (0.76 with a range 0.35-0.94). The correlation between the agronomical dissimilarity matrix and the matrices of genetic dissimilarity based on SSR and AFLP markers was very weak: 0.156 (p = 0.05) and 0.185 (p = 0.05), respectively. The SSR-AFLP dendrogram based on unweighted pair-group cluster analysis using Jaccard\u2019s index revealed that the genetic diversity was predominantly structured according to fruit size. A trend of clustering together of accessions originating from the same or adjacent regions was also observed. The data obtained can be used for the varietal survey and construction of a database of all olive varieties grown in Tunisia and providing also additional information that could form the basis for the rational design of breeding programs

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

Cross-Priming Approach Induced Beneficial Metabolic Adjustments and Repair Processes during Subsequent Drought in Olive

Cross-tolerance to abiotic stresses is a typical phenomenon in plants which occurs when exposure to one form of stress confers tolerance to a variety of stresses. Our study aims at investigating whether salinity priming could induce, after a recovery period (2 months), drought tolerance in olive cv. Chétoui. Here, our results revealed that this method of cross-adaptation had further enhanced the olive’s subsequent response to drought. In fact, relative to the non-pretreated plants, the salt-pretreated ones displayed an enhancement in terms of shoot biomass accumulation, photosynthetic performance, water-use efficiency, and hydration status. Furthermore, the attenuation of oxidative stress and the maintenance of structural lipid contents, as well as their fatty acid composition in salt-pretreated plants, also supported the beneficial effect of this method. From our results, it seems that salt priming substantially modulated the physiological and biochemical responses of olive plants to subsequent drought. Accordingly, metabolite adjustments (soluble sugars and proline), the enzymatic antioxidant system (superoxide dismutase (SOD), catalase (CAT), and guaiacol peroxidase (GP) activities) as well as the nonenzymatic one (phenols), and the increase in leaf density together with the raise of structural lipids content, to a lesser extent, seemed to perform a major role in the development of this improved tolerance to drought. The ameliorative response found in salt-primed olive plants, when subsequently exposed to drought, indicates an efficient cross-tolerance reaction. This could be particularly important in the Mediterranean area, where olive orchards are mainly cultivated under dry-land farming management

Agronomic and molecular analyses for the characterisation of accessions in Tunisian olive germplasm collections

In this study, a total of 14 agronomic traits, five AFLP primer combinations and ten SSR loci were used to describe and to classify a group of Tunisian olive genotypes into groups based on molecular profiles and agronomic traits. The analysis of variance of the agronomical data revealed significant differences among accessions for all measured traits. The mean phenotypic dissimilarity (0.34 with a range of 0.08-0.6) was low in comparison to dissimilarity calculated using AFLP (0.50 with a range of 0.16-0.70) and SSR markers (0.76 with a range 0.35-0.94). The correlation between the agronomical dissimilarity matrix and the matrices of genetic dissimilarity based on SSR and AFLP markers was very weak: 0.156 (p = 0.05) and 0.185 (p = 0.05), respectively. The SSR-AFLP dendrogram based on unweighted pair-group cluster analysis using Jaccard’s index revealed that the genetic diversity was predominantly structured according to fruit size. A trend of clustering together of accessions originating from the same or adjacent regions was also observed. The data obtained can be used for the varietal survey and construction of a database of all olive varieties grown in Tunisia and providing also additional information that could form the basis for the rational design of breeding programs

Monitoring the volatile and hydrophilic bioactive compounds status of fresh and oxidized Chemlali virgin olive oils over olive storage times

The virgin olive oils (VOOs) under examination were from the main Tunisian cultivar ‘Chemlali’. Olive fruits used for oil production were stored in plastic containers for four weeks at ambient temperature. Hydrophilic bioactive compounds and volatile profiles of the corresponding oils were analyzed. Chemometric analysis showed that VOO obtained from fruits stored during one week is similar to that of freshly harvested fruits. They preserved their bioactive and volatile molecular markers of freshness with the predominance of the secoiridoid aldehydic form of oleuropeine aglycon, and the C6⁠ lipoxygenase products. However, VOO obtained from fruits stored for a long time, showed degradation of the derivatives of oleuropeine and ligstro- side aglycons, a decrease in the lignan, and flavonoid groups, whereas phenolic acids showed a remarkable in- crease. The volatile profile was characterized by a decrease in the LOX products, and biosynthesis of the volatile molecular markers of oxidation C7⁠ -C1⁠ 0 aldehydes (nonanal, decanal, (Z) and (E)-2-heptenal, (E)-2-octenal, and (E,E)-2,4-heptadienal), and hydrocarbons (n-dodecane, and n-tetradecane). Mono and sesquiterpenes showed also an increase over storage time. Consequently, and in order to avoid deterioration of VOO composition, chemometric analysis showed that the olive fruits should be processed as soon as possible after being harvested, with a maximum storage time of one week

Phenolic composition as measured by liquid chromatography/mass spectrometry and biological properties of Tunisian barley

In this work, phenolic composition, antioxidant and antibacterial activities of selected Tunisian barley varieties were studied. Swihli barley exhibited the highest total phenolic content and the strongest antioxidant and antibacterial activities. Liquid chromatography/mass spectrometry analysis revealed significant qualitative and quantitative differences in phenolic composition among the different varieties. Procyanidin B3 and catechin were the most abundant. Pearson\u2019s correlation test revealed significant correlations between the antioxidant activities of barley extracts and both hydroferuloyl glucose and catechin-3-glucose

Oil fatty acid composition of eighteen Mediterranean olive varieties cultivated under the arid conditions of Boughrara (southern Tunisia)

In this study, eighteen olive varieties, originating from Spain, France, Italy, Greece and Algeria, and maintained at the olive experimental station of Boughrara (arid region of Tunisia) were evaluated for their oil yield and fatty acid composition. The analysis of variance revealed significant differences among varieties for all traits (p < 0.01). The Hierarchical Cluster Analysis (HCA) classified the varieties into three main groups. The first group included a subgroup which is composed of seven olive varieties (Cornezuelo, Verdial de Vélez-Málaga, Leccino, Coratina, Koroneiki, Lechín de Granada and Changlot Real) characterized by high oil yield with high oleic, low palmitic and linoleic acid contents. The fatty acid compositions of the oils from these varieties comply with international standards and show more beneficial characteristics than the oil obtained from Chemlali: the most abundant olive cultivar in Tunisia. Finally, the main fatty acids (palmitic (C16:0), oleic (C18:1) and linoleic (C18:2)) of nine of the studied virgin olive oils were compared to those sampled from their traditional areas. Except for Koroneiki and Olivière oils which showed an unchanged fatty acid composition and for Cornezuelo oil in which the level of oleic acid raised and the level of linoleic acid decreased, most of oils showed a decrease in oleic acid rates and an increase in palmitic and linoleic acid percentages as compared to those from their original sites.<br><br>En este estudio, dieciocho variedades de aceituna procedentes de España, de Francia, de Italia, de Grecia y de Argelia, cultivadas en la estación experimental del olivo de Boughrara (región árida de Túnez), fueron evaluadas para el rendimiento en aceite y la composición de ácidos grasos. El análisis de la varianza mostró diferencias significativas entre todas las variedades (p < 0.01). El análisis de “clusters” jerárquico clasificó las variedades en tres grandes grupos. El primer grupo incluía un subgrupo compuesto por siete variedades de aceituna Changlot Real, Koroneiki, Verdial de Vélez- Málaga, Coratina, Lechín de Granada, Cornezuelo y Leccino, que se caracterizan por su alto rendimiento en aceite, alto contenido en oleico y bajo contenido en ácidos palmítico y linoleico. Las composiciones de ácidos grasos de aceites provenientes de estas variedades se conforman con estándares internacionales y son mejores si las comparamos con la de Chemlali (el cultivo más abundante en Túnez). Finalmente, los ácidos grasos mayoritarios (palmítico (C16:0), oleico (C18:1) y linoleico (C18:2)) de nueve de los aceites de oliva virgen estudiados fueron comparados con los de las mismas variedades cultivadas en sus áreas originarias. A excepción de los aceites Koroneiki y Olivière que mostraron una composición de ácidos grasos inalterable y del aceite Cornezuelo en el que se observó un aumento del nivel de ácido oleico y un descenso del nivel de ácido linoleico, la mayoría de los aceites mostró disminución de ácido oleico y aumento de los porcentajes de ácido palmítico y linoleico, comparándolos con los obtenidos de las aceitunas cultivadas en su lugares de origen