Discovering new genes for alfalfa (Medicago sativa) growth and biomass resilience in combined salinity and Phoma medicaginis infection through GWAS.

Salinity and Phoma medicaginis infection represent significant challenges for alfalfa cultivation in South Africa, Europe, Australia, and, particularly, Tunisia. These constraints have a severe impact on both yield and quality. The primary aim of this study was to establish the genetic basis of traits associated with biomass and growth of 129 Medicago sativa genotypes through genome-wide association studies (GWAS) under combined salt and P. medicaginis infection stresses. The results of the analysis of variance (ANOVA) indicated that the variation in these traits could be primarily attributed to genotype effects. Among the test genotypes, the length of the main stem, the number of ramifications, the number of chlorotic leaves, and the aerial fresh weight exhibited the most significant variation. The broad-sense heritability (H²) was relatively high for most of the assessed traits, primarily due to genetic factors. Cluster analysis, applied to morpho-physiological traits under the combined stresses, revealed three major groups of accessions. Subsequently, a GWAS analysis was conducted to validate significant associations between 54,866 SNP-filtered single-nucleotide polymorphisms (SNPs) and seven traits. The study identified 27 SNPs that were significantly associated with the following traits: number of healthy leaves (two SNPs), number of chlorotic leaves (five SNPs), number of infected necrotic leaves (three SNPs), aerial fresh weight (six SNPs), aerial dry weight (nine SNPs), number of ramifications (one SNP), and length of the main stem (one SNP). Some of these markers are related to the ionic transporters, cell membrane rigidity (related to salinity tolerance), and the NBS_LRR gene family (associated with disease resistance). These findings underscore the potential for selecting alfalfa genotypes with tolerance to the combined constraints of salinity and P. medicaginis infection.

Essential Oils and Biological Activities of Eucalyptus falcata, E. sideroxylon and E. citriodora Growing in Tunisia.

Many plants are able to synthesize essential oils (EOs), which play key roles in defense against weeds, fungi and pests. This study aims to analyze the chemical composition and to highlight the antioxidant, antimicrobial and phytotoxic properties of the EOs from Eucalyptus falcata, E. sideroxylon and E. citriodora growing in Tunisia. EOs were analyzed by gas chromatography coupled to mass spectrometry (GC/MS) and their antioxidant properties were determined by total antioxidant capacity (TAC), DPPH and ABTS assays. The phytotoxic potential was assessed against weeds (Sinapis arvensis, Phalaris canariensis) and durum wheat crop (Triticum durum) and compared to chemical herbicide glyphosate. The antifungal activity was investigated in vitro against eight target fungal strains. All EOs displayed a specific richness in oxygenated monoterpenes (51.3-90%) and oxygenated sesquiterpenes (4.8-29.4%), and 1,8-cineole, citronellal, citronellol, trans-pinocarveol, globulol, spathulenol and citronellyl acetate were the main constituents. Eucalyptus EOs exhibited remarkable antioxidant activity and E. citriodora oil exhibited significant activity when compared with E. falcata and E. sideroxylon EOs. The phytotoxic potential of the tested oils had different efficacy on seed germination and the growth of seedlings and varied among tested herbs and their chemical composition variability. Their effectiveness was better than that of glyphosate. At the post-emergence stage, symptoms of chlorosis and necrosis were observed. Furthermore, a decrease in chlorophyll and relative water content, electrolyte leakage and high levels of MDA and proline were indicators of the oxidative effects of EOs and their effectiveness as bioherbicides. Moreover, all the EOs exhibited moderate fungitoxic properties against all the tested fungal strains. Therefore, according to the obtained results, Eucalyptus EOs could have potential application as natural pesticides.

NaCl effect on Cd accumulation and cell compartmentalization in barley.

The effect of sodium chloride (NaCl) on cadmium (Cd) tolerance, uptake, translocation, and compartmentation was investigated in 3 barley genotypes. Seedlings were cultivated hydroponically in the absence of NaCl and Cd (control), in the presence of 50 mM NaCl alone, in the presence of 10 µM Cd alone, and in the combined addition of NaCl (50 mM) and Cd (10 µM). Plants were cultivated during one month under 16 h light period at a minimal light intensity of 250 µmol m-2 s-1, a temperature of 25 ± 3 °C, and 70-80% of relative humidity. Results showed that NaCl alone did not significantly affect plant development and biomass production; however, Cd alone reduced plant development rate leading to a decline in biomass production in Raihane and Giza 127 but did not affect that in Amalou. NaCl addition in Cd-treated plants accentuated the Cd effect on plant growth. NaCl limited Cd accumulation in the roots and in the shoots in all tested barley varieties by reducing Cd-absorption efficiency and the translocation of Cd from the root to the shoot. In all Cd-treated plants, cell Cd compartmentalization showed the following gradient: organelles < cell wall < vacuole. NaCl in the medium increased Cd accumulation in the soluble fraction and reduced that in organelle and cell wall fractions. Globally our results showed that, although NaCl reduces Cd accumulation in barley, it accentuates the Cd toxic effects, hence limiting the plant yield. We advise farmers to avoid barley cultivation near mine sites and its irrigation with moderately salty water, although this plant is considered as salt tolerant.

Improved growth and tuber quality of transgenic potato plants overexpressing either NHX antiporter, CLC chloride channel, or both.

The nutritional enhancement of potato plants (Solanum tuberosum L.,) is highly critical. As it is considered a worldwide basic vegetarian nutrition to maintain health. S. tuberosum is one of the foremost staples and the world's fourth-largest food crop. In advance, its need is increasing because of its high-industrial value and population blast. To improve both potato growth and behavior under harsh environmental conditions, we produced transgenic potato plants overexpressing either VvNHX (a sodium proton antiporter from Vitis vinifera), VvCLC (a chloride channel from Vitis vinifera), or both. Control and transgenic plants were grown in greenhouse and field under non-stressed conditions for 85 days in order to characterize their phenotype and evaluate their agronomical performance. To this aim, the evaluation of plant growth parameters, tuber yields and characteristics (calibers, eye number and color), the chemical composition of tubers, was conducted and compared between the different lines. The obtained results showed that transgenic plants displayed an improved growth (flowering precocity, gain of vigor and better vegetative growth) along with enhanced tuber yields and quality (increased protein and starch contents). Our findings provide then insight into the role played by the VvNHX antiport and the VvCLC channel and a greater understanding of the effect of their overexpression in potato plants.

Integration of Innovative Technologies in the Agri-Food Sector: The Fundamentals and Practical Case of DNA-Based Traceability of Olives from Fruit to Oil.

Several socio-economic problems have been hidden by the COVID-19 pandemic crisis. Particularly, the agricultural and food industrial sectors have been harshly affected by this devastating disease. Moreover, with the worldwide population increase and the agricultural production technologies being inefficient or obsolete, there is a great need to find new and successful ways to fulfill the increasing food demand. A new era of agriculture and food industry is forthcoming, with revolutionary concepts, processes and technologies, referred to as Agri-food 4.0, which enables the next level of agri-food production and trade. In addition, consumers are becoming more and more aware about the origin, traceability, healthy and high-quality of agri-food products. The integration of new process of production and data management is a mandatory step to meet consumer and market requirements. DNA traceability may provide strong approach to certify and authenticate healthy food products, particularly for olive oil. With this approach, the origin and authenticity of products are confirmed by the means of unique nucleic acid sequences. Selected tools, methods and technologies involved in and contributing to the advance of the agri-food sector are presented and discussed in this paper. Moreover, the application of DNA traceability as an innovative approach to authenticate olive products is reported in this paper as an application and promising case of smart agriculture.

Comparative Analysis and Structural Modeling of Elaeis oleifera FAD2, a Fatty Acid Desaturase Involved in Unsaturated Fatty Acid Composition of American Oil Palm.

American oil palm (Elaeis oleifera) is an important source of dietary oil that could fulfill the increasing worldwide demand for cooking oil. Therefore, improving its production is crucial and could be realized through breeding and genetic engineering approaches aiming to obtain high-yielding varieties with improved oil content and quality. The fatty acid composition and particularly the oleic/linoleic acid ratio are major factors influencing oil quality. Our work focused on a fatty acid desaturase (FAD) enzyme involved in the desaturation and conversion of oleic acid to linoleic acid. Following the in silico identification and annotation of Elaeis oleifera FAD2, its molecular and structural features characterization was performed to better understand the mechanistic bases of its enzymatic activity. EoFAD2 is 1173 nucleotides long and encodes a protein of 390 amino acids that shares similarities with other FADs. Interestingly, the phylogenetic study showed three distinguished groups where EoFAD2 clustered among monocotyledonous taxa. EoFAD2 is a membrane-bound protein with five transmembrane domains presumably located in the endoplasmic reticulum. The homodimer organization model of EoFAD2 enzyme and substrates and respective substrate-binding residues were predicted and described. Moreover, the comparison between 24 FAD2 sequences from different species generated two interesting single-nucleotide polymorphisms (SNPs) associated with the oleic/linoleic acid contents.

Halophytes.tn: an innovative database for Tunisian halophyte plant identification, distribution and characterization.

Halophytes.tn (http://halophytes.rnrt.tn/) is a web-based database of Tunisian halophyte species. Halophytes are salt-tolerant plants able to grow above 85 mM of salt, even up to 2 M as for Tecticornia spp. Tunisia, a North African country located on the Mediterranean border, covering ∼165 000 km2, harbors several types of saline habitats and biotopes where halophytes preferably vegetate. With ∼6000 worldwide and over 420 Tunisian species, halophytes represent a huge potential in several fields, including desalination, phytoremediation, agrofarming, medicinal use, industrial applications, pharmacology and even nanotechnology. We describe the practical and technical steps followed and bioinformatics tools used to conceive and design the first Tunisian halophytes database, enabling species identification and characterization. As a first version, information about botany, morphology, ecophysiology and biochemistry were provided for the identified species with their sites of growing in Tunisia, first step of biodiversity conservation, management and valorization. The database will be regularly maintained, updated and enriched to achieve the goal of whole Tunisian halophyte species and fit the needs of scientists and all category of users.Database URL: http://halophytes.rnrt.tn/.

SNP discovery and structural insights into OeFAD2 unravelling high oleic/linoleic ratio in olive oil.

Fatty Acid Desaturase 2 (FAD2), a key enzyme in the fatty acid biosynthesis pathway, is involved in the desaturation and conversion of oleic acid to linoleic acid. Therefore, it plays a crucial role in oleic/linoleic acid ratio and the quality of olive oil. DNA sequencing of 19 FAD2 genes from a set of olive oil varieties revealed several single-nucleotide polymorphisms (SNPs) and highlighted associations between some of the SNPs and saturated fatty acids contents. This was further confirmed by SNP-interaction and machine learning approach. Haplotype diversity analysis led to the discovery of three highly polymorphic SNPs and four haplotypes harboring differential oleic/linoleic acid ratios. Moreover, a combination of molecular modeling and docking experiments allowed a deeper and better understanding of the structure-function relationship of the FAD2 enzyme. Sequence patterns and variations involved in the regulation of the FAD2 activity were also identified. Furthermore, S82C and H213N substitutions in OeFAD2 make the Oueslati variety more interesting in terms of fatty acid profile and oleic acid level.

Assessment of population structure, genetic diversity and relationship of Mediterranean olive accessions using SSR markers and computational tools.

Olive tree is an emblematic crop of the Mediterranean region, mainly renowned for its fruit oil, although the species provides several industrial purposes. The Mediterranean basin constitutes the origin of olive species diversification and represents a valuable source of genetic variability of olive germplasm. Therefore, the evaluation of the diversity and the population structure of this Mediterranean germplasm is a challenge for olive species preservation, crop breeding and genetic improvement. In this context, our study aims to analyze the genetic diversity and the population structure of 79 Mediterranean olive accessions using 15 genomic SSRs and by applying computational model-based approaches. The used SSRs revealed a total number of 225 alleles with a mean of 15 alleles per locus. Observed and expected heterozygosity (Ho = 0.79, He = 0.805) with a Polymorphism Information Content value of 0.775 indicate high level of genetic diversity. All results of the Unweighted Pair Group Method with Arithmetic (UPGMA), Jaccard similarity index, Principal Coordinate Analysis (PCoA) and the Bayesian analyses supported the separation of the Mediterranean varieties in two sub-populations, one of which mainly composed by Spanish accessions.

Evaluation of the Morpho-Physiological, Biochemical and Molecular Responses of Contrasting Medicago truncatula Lines under Water Deficit Stress.

Medicago truncatula is a forage crop of choice for farmers, and it is a model species for molecular research. The growth and development and subsequent yields are limited by water availability mainly in arid and semi-arid regions. Our study aims to evaluate the morpho-physiological, biochemical and molecular responses to water deficit stress in four lines (TN6.18, JA17, TN1.11 and A10) of M. truncatula. The results showed that the treatment factor explained the majority of the variation for the measured traits. It appeared that the line A10 was the most sensitive and therefore adversely affected by water deficit stress, which reduced its growth and yield parameters, whereas the tolerant line TN6.18 exhibited the highest root biomass production, a significantly higher increase in its total protein and soluble sugar contents, and lower levels of lipid peroxidation with greater cell membrane integrity. The expression analysis of the DREB1B gene using RT-qPCR revealed a tissue-differential expression in the four lines under osmotic stress, with a higher induction rate in roots of TN6.18 and JA17 than in A10 roots, suggesting a key role for DREB1B in water deficit tolerance in M. truncatula.

Morpho-Physiological, Biochemical, and Genetic Responses to Salinity in Medicago truncatula.

We used an integrated morpho-physiological, biochemical, and genetic approach to investigate the salt responses of four lines (TN1.11, TN6.18, JA17, and A10) of Medicago truncatula. Results showed that TN1.11 exhibited a high tolerance to salinity, compared with the other lines, recording a salinity induced an increase in soluble sugars and soluble proteins, a slight decrease in malondialdehyde (MDA) accumulation, and less reduction in plant biomass. TN6.18 was the most susceptible to salinity as it showed less plant weight, had elevated levels of MDA, and lower levels of soluble sugars and soluble proteins under salt stress. As transcription factors of the APETALA2/ethylene responsive factor (AP2/ERF) family play important roles in plant growth, development, and responses to biotic and abiotic stresses, we performed a functional characterization of MtERF1 gene. Real-time PCR analysis revealed that MtERF1 is mainly expressed in roots and is inducible by NaCl and low temperature. Additionally, under salt stress, a greater increase in the expression of MtERF1 was found in TN1.11 plants than that in TN6.18. Therefore, the MtERF1 pattern of expression may provide a useful marker for discriminating among lines of M. truncatula and can be used as a tool in breeding programs aiming at obtaining Medicago lines with improved salt tolerance.

Genome Wide Identification, Molecular Characterization, and Gene Expression Analyses of Grapevine NHX Antiporters Suggest Their Involvement in Growth, Ripening, Seed Dormancy, and Stress Response.

Plant NHX antiporters are critical for cellular pH, Na+, and K+ homeostasis and salt tolerance. Even though their genomic and functional studies have been conducted in many species, the grapevine NHX family has not been described yet. Our work highlights the presence of six VvNHX genes whose phylogenetic analysis revealed their classification in two distinct groups: group I vacuolar (VvNHX1-5) and group II endosomal (VvNHX6). Several cis-acting regulatory elements related to tissue-specific expression, transcription factor binding, abiotic/biotic stresses response, and light regulation elements were identified in their promoter. Expression profile analyses of VvNHX genes showed variable transcription within organs and tissues with diverse patterns according to biochemical, environmental, and biotic treatments. All VvNHXs are involved in berry growth, except VvNHX5 that seems to be rather implicated in seed maturation. VvNHX4 would be more involved in floral development, while VvNHX2 and 3 display redundant roles. QPCR expression analyses of VvNHX1 showed its induction by NaCl and KNO3 treatments, whereas VvNHX6 was induced by ABA application and strongly repressed by PEG treatment. VvNHX1 plays a crucial role in a bunch of grape developmental steps and adaptation responses through mechanisms of phyto-hormonal signaling. Overall, VvNHX family members could be valuable candidate genes for grapevine improvement.

Quality selection and genetic diversity of Tunisian durum wheat varieties using SSR markers / Seleção de qualidade e diversidade genética de vari edades de trigo duro da tunísia usando marcadores SSR

Our study focuses on the molecular analysis of the genetic diversity within 15 Tunisian durum wheat varieties and the assessment of the efficiency of some available markers to select valuable genotypes for technological proprieties of semolina (i.e. parameters related to SDS-sedimentation, mixing time and breakdown resistance of mixograph, grain protein content and yellow colour). While several markers were validated, others were not informative within the genotypes used. A high level of polymorphic information content (PIC) was detected, with an average of 5.2 polymorph alleles per locus and 0.6 average. Old varieties have high protein content however; modern varieties display strong gluten strength. Our results thus open the opportunity to choose valuable parents on the base of pedigrees, technological properties and genetic distances; and lead us to select efficient markers for the Regional Indigenous Land Strategy (Rils) selection strategy

Nosso estudo enfoca a análise molecular da diversidade genética em 15 variedades de trigo duro tunisiano e a avaliação da eficiência de alguns marcadores disponíveis para selecionar genótipos valiosos para propriedades tecnológicas de semolina (ou seja, parâmetros relacionados à sedimentação sds, tempo de mistura e resistência à degradação do mixógrafo, teor de proteína dos grãos e cor amarela). Enquanto vários marcadores foram validados, outros não foram informativos dentro dos genótipos utilizados. Foi detectado um alto nível de conteúdo de informação polimórfica (pic), com uma média de 5,2 alelos polimórficos por locus e 0,6 média. Variedades antigas têm alto teor de proteína no entanto; variedades modernas exibem forte força de glúten. Nossos resultados abrem, assim, a oportunidade de escolher pais valiosos com base em pedigrees, propriedades tecnológicas e distâncias genéticas; e nos levam a selecionar marcadores eficientes para a estratégia de seleção da estratégia regional de terras indígenas (rils).

Computational Approach for Structural Feature Determination of Grapevine NHX Antiporters.

Plant NHX antiporters are responsible for monovalent cation/H+ exchange across cellular membranes and play therefore a critical role for cellular pH regulation, Na+ and K+ homeostasis, and salt tolerance. Six members of grapevine NHX family (VvNHX1-6) have been structurally characterized. Phylogenetic analysis revealed their organization in two groups: VvNHX1-5 belonging to group I (vacuolar) and VvNHX6 belonging to group II (endosomal). Conserved domain analysis of these VvNHXs indicates the presence of different kinds of domains. Out of these, two domains function as monovalent cation-proton antiporters and one as the aspartate-alanine exchange; the remaining are not yet with defined function. Overall, VvNHXs proteins are typically made of 11-13 putative transmembrane regions at their N-terminus which contain the consensus amiloride-binding domain in the 3rd TM domain and a cation-binding site in between the 5th and 6th TM domain, followed by a hydrophilic C-terminus that is the target of several and diverse regulatory posttranslational modifications. Using a combination of primary structure analysis, secondary structure alignments, and the tertiary structural models, the VvNHXs revealed mainly 18 α helices although without ß sheets. Homology modeling of the 3D structure showed that VvNHX antiporters are similar to the bacterial sodium proton antiporters MjNhaP1 (Methanocaldococcus jannaschii) and PaNhaP (Pyrococcus abyssi).

Nutraceutical potentialities of Tunisian Argan oil based on its physicochemical properties and fatty acid content as assessed through Bayesian network analyses.

BACKGROUND: Argan oil is traditionally produced by cold pressing in South-western Morocco where rural population uses it as edible oil as well as for its therapeutic properties which give them in counterpart valuable income. Given the economical interest of this oil, several attempts of fraudulency have been registered in the world global market leading to loss of authenticity. Our purpose is to launch a program of Tunisian Argan oil valorization since trees from this species have been introduced sixty years ago in Tunisia. The first step was thus to characterize the physicochemical properties and determine the chemical composition of Tunisian Argan oil in order to assess its quality. METHODS: Physicochemical parameters of oil quality were determined according to the international standard protocols. Fatty acid content analysis of Argan oils was performed by gas chromatography coupled to mass spectrophotometry. A comparative study was realized among Tunisian, Moroccan and Algerian samples differing also by their extraction procedure. The impact of geographical localisation on the fatty acids composition was studied by statistical and modeling Bayesian analyses. RESULTS: Physicochemical parameters analysis showed interestingly that Tunisian Argan oil could be classified as extra virgin oil. Argan oil is mainly composed by unsaturated fatty acids (80%), mainly oleic and linoleic acid (linoleic acid was positively influenced by the geographical localization (r = 0.899, p = 0.038) and the P/S index (r = 0.987, p = 0.002)) followed by saturated fatty acids (20%) with other beneficial compounds from the unsaponifiable fraction like polyphenols and carotenoids. Together with fatty acid content, these minor components are likely to be responsible for its nutraceutical properties and beneficial effects. CONCLUSION: Tunisian Argan oil displayed valuable qualitative parameters proving its competitiveness in comparison with Moroccan and Algerian oils, and could be therefore considered as extra virgin edible oil for nutraceutical purposes as well as for cosmetic use.

The grapevine VvWRKY2 gene enhances salt and osmotic stress tolerance in transgenic Nicotiana tabacum.

Our study aims to assess the implication of WRKY transcription factor in the molecular mechanisms of grapevine adaptation to salt and water stresses. In this respect, a full-length VvWRKY2 cDNA, isolated from a Vitis vinifera grape berry cDNA library, was constitutively over-expressed in Nicotiana tabacum seedlings. Our results showed that transgenic tobacco plants exhibited higher seed germination rates and better growth, under both salt and osmotic stress treatments, when compared to wild type plants. Furthermore, our analyses demonstrated that, under stress conditions, transgenic plants accumulated more osmolytes, such as soluble sugars and free proline, while no changes were observed regarding electrolyte leakage, H2O2, and malondialdehyde contents. The improvement of osmotic adjustment may be an important mechanism underlying the role of VvWRKY2 in promoting tolerance and adaptation to abiotic stresses. Principal component analysis of our results highlighted a clear partition of plant response to stress. On the other hand, we observed a significant adaptation behaviour response for transgenic lines under stress. Taken together, all our findings suggest that over-expression of VvWRKY2 gene has a compelling role in abiotic stress tolerance and, therefore, would provide a useful strategy to promote abiotic stress tolerance in grape via molecular-assisted breeding and/or new biotechnology tools.

First study of correlation between oleic acid content and SAD gene polymorphism in olive oil samples through statistical and bayesian modeling analyses.

BACKGROUND: Virgin olive oil is appreciated for its particular aroma and taste and is recognized worldwide for its nutritional value and health benefits. The olive oil contains a vast range of healthy compounds such as monounsaturated free fatty acids, especially, oleic acid. The SAD.1 polymorphism localized in the Stearoyl-acyl carrier protein desaturase gene (SAD) was genotyped and showed that it is associated with the oleic acid composition of olive oil samples. However, the effect of polymorphisms in fatty acid-related genes on olive oil monounsaturated and saturated fatty acids distribution in the Tunisian olive oil varieties is not understood. METHODS: Seventeen Tunisian olive-tree varieties were selected for fatty acid content analysis by gas chromatography. The association of SAD.1 genotypes with the fatty acids composition was studied by statistical and Bayesian modeling analyses. RESULTS: Fatty acid content analysis showed interestingly that some Tunisian virgin olive oil varieties could be classified as a functional food and nutraceuticals due to their particular richness in oleic acid. In fact, the TT-SAD.1 genotype was found to be associated with a higher proportion of mono-unsaturated fatty acids (MUFA), mainly oleic acid (C18:1) (r = - 0.79, p < 0.000) as well as lower proportion of palmitic acid (C16:0) (r = 0.51, p = 0.037), making varieties with this genotype (i.e. Zarrazi and Tounsi) producing more monounsaturated oleic acid (C18: 1) than saturated acid. These varieties could be thus used as nutraceuticals and functional food. CONCLUSION: The SAD.1 association with the oleic acid composition of olive oil was identified among the studied varieties. This correlation fluctuated between studied varieties, which might elucidate variability in lipidic composition among them and therefore reflecting genetic diversity through differences in gene expression and biochemical pathways. SAD locus would represent an excellent marker for identifying interesting amongst virgin olive oil lipidic composition.

Identification and characterization of single nucleotide polymorphism markers in FADS2 gene associated with olive oil fatty acids composition.

BACKGROUND: Genotyping of the FAD2.1 and FAD2.3 polymorphisms in the fatty acid desaturase 2 gene (FADS2) shows that they are associated with the fatty acids composition of olive oil samples. However, these associations require further confirmation in the Tunisian olive oil cultivars, and little is known about the effect of polymorphisms in fatty acid-related genes on olive oil mono- and poly- unsaturated fatty acids distribution. METHODS: A set of olive oils from 12 Tunisian cultivars was chosen. The fatty acid composition of each olive oil sample was determined by gas chromatography. Statistical and modeling Bayesian analyses were used to assess whether the FAD2.1 and FAD2.3 genotypes were associated with fatty acids composition. RESULTS: The TT-FAD2.1 and the GG-FAD2.3 genotypes were found to be associated with a lower proportion of oleic acid (C18:1) (r = -0.778, p = 0.003; r = -0.781, p= 0.003) as well as higher proportion of linoleic (C18:2) (r = 0.693, p = 0.012; r = -0.759, p= 0.004) and palmitic acids (C16:0) (r = 0.643, p = 0.024; r = -0.503, p= 0.095), making varieties with this haplotype (i.e. Chemlali Sfax and Meski) producing more saturated (C16: 0) and polyunsaturated acids than oleic acid. The latter plays a major role in preventing several diseases. CONCLUSION: The two associations FADS2 FAD2.1 and FADS2 FAD2.3 with the fatty acid compositions of olive oil samples were identified among the studied olive cultivars. These associations differed between studied cultivars, which might explain variability in lipidic composition among them and consequently reflecting genetic diversity through differences in gene expression and biochemical pathways. FADS2 locus would constitute thus a good marker for detecting interesting lipidic chemotypes among commercial olive oils.

Study of allelopathic effects of Eucalyptus erythrocorys L. crude extracts against germination and seedling growth of weeds and wheat.

Allelopathic materials inside a tree can produce positive or negative change in the survival, growth, reproduction and behaviour of other organisms if they escape into the environment. To assess these effects, this work was carried out to evaluate the allelopathic impact of Eucalyptus erythrocorys L. on seed germination and seedling growth of two weeds: Sinapis arvensis L. and Phalaris canariensis L.; on one cultivated crop: Triticum durum L. Aqueous; and on ethanolic leaf extracts of E. erythrocorys L. The study was effected using four concentrations (10, 20, 25 and 30 µL/mL) while distilled water was used as a control. The results showed that the E. erythrocorys L. crude extracts had an inhibitory effect on seed germination and seedling growth of both studied weeds and wheat. The inhibition rate was increased by the increase in extract concentration. Only ethanolic extracts of E. erythrocorys L. induced a significant inhibition of seed germination of durum wheat. The effect of E. erythrocorys L. crude extracts was more severe on weeds than on durum wheat. These results indicate that the seedling growth, especially radicle elongation, was the more sensitive indicator to evaluate the effects of extracts than was the seed germination.