Tunisian Barley Research Articles

Chloroplast DNA Diversity of Tunisian Barley Landraces as Revealed by cpSSRs Molecular Markers and Implication for Conservation Strategies.

In Tunisia, barley local landraces are still cropped for human and animal consumption in some subsistence farming systems under marginal and stressed conditions. These high-value genetic resources present a potential source of resistance genes to biotic and abiotic stresses useful for both national and international breeders. Actually, they are represented by threatened small populations, which face a high risk of genetic erosion and progressive substitution by modern varieties. In this study, the genetic diversity of 60 Tunisian barley landraces was assessed using six chloroplast microsatellites. All loci were found polymorphic, with 2 or 3 alleles per locus. Thirteen alleles were detected across the studied sample, which were combined into 8 haplotypes, giving a haplotype diversity (Hd) of 0.847. High punctual and haplotype genetic diversity was observed for Tunisian barley landraces when compared to other germplasms from other regions of the world. The genetic structure analysis revealed two major clusters of Tunisian barley landraces, which confirms their multiorigin. This result was corroborated by the median-joining network showing the genetic relationships among the eight detected haplotypes. The AMOVA analysis revealed that 83% of the genetic variation is between populations, which requires the in situ and ex situ conservation of plant material for all Tunisian populations of barley landraces. Information on genetic variation within the chloroplast genome is of great interest to ensure an efficient conservation strategy that takes into account the preservation of the various maternal lineages of Tunisian barley.

Physicochemical characterization, antioxidant activity and phenolic acids profile of Tunisian whole cereal grains

Six varieties of Tunisian durum wheat, barley and oat cultivars namely Maali, Karim, Rihane, Manel, Meliane and Ghzella were analyzed for their physicochemical properties, antioxidant activities and phenolic acids profile. Results showed that there are significant (p < 0.05) differences in moisture (11.8-12.8%), proteins (10.98-12.09%), neutral detergent fibre (NDF) (47.67-67.39%), ash (2.4-3.93%), fat (2.6- 6.75%), and carbohydrates (64.78-70.95%) contents between all studied varieties. Cereal grains were also a good source of potassium, sodium, calcium, zinc and iron. The results revealed that oat Meliane (5.9%) and barley Rihane (5.4%) varieties are good sources of dietary fiber β-glucan compared to the other varieties. Rihane, Meliane and Maali varieties had the highest total phenolic, total flavonoids and total condensed tannin contents. Antioxidant activity of whole grain extracts was performed using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) test and revealed that barley Rihane had the best radical scavenging activity compared to oat and durum wheat varieties. The RP-HPLC analysis revealed that Tunisian barley, oat and durum wheat varieties are a good source of phenolic components and natural antioxidants.

Assessment of the physio-biochemical performance of Tunisian barley landraces under deficit saline-irrigation during grain filling stage

Salinity is one of the main and important abiotic stresses that adversely affects crop growth, development and production. In this study, two barley (Hordeum vulgare L.) landraces were subjected to three treatments of deficit saline-irrigation (12 dS/cm) (T0 = 100%ETc, T1 = 75%ETc, and T2 = 50%ETc) during grain filling stage. Carbon isotope discrimination (Δ13C) was associated with some physio-biochemical parameters to evaluate barley response to saline conditions. Results of this study showed that deficit saline-irrigation significantly (p < 0.05) decreases Δ13C in both barley landraces. Moreover, photosynthetic rate (A), transpiration (E), stomatal conductance (gs), and instantaneous water use efficiency (iWUE) were significantly affected by treatments. Relative water content (RWC), chlorophyll a, and chlorophyll (SPAD) value were significantly (p < 0.01 and p < 0.001) were affected by deficit saline-irrigation. In addition, phenolic compounds were affected by treatments and landraces (except syringic and p-coumaric acids), and their interactions (except syringic acid). Moreover, high correlations were noticed between Δ13C and physio-biochemical parameters. Results suggested that both barley landraces make a higher iWUE, and a weak variation in phenolic compounds. Moreover, Δ13C associated with physio-biochemical traits can also be good criteria for screening of salt-tolerance of barley during grain filling stage. Taken together, our study suggests that the response to deficit saline-irrigation in barley landraces involves an interplay between various physiological and biochemical mechanisms mainly related to Δ13C.

A Nutritional Survey of Local Barley Populations Based on the Mineral Bioavailability, Fatty Acid Profile, and Geographic Distribution of Fusarium Species and the Mycotoxin Zearalenone (ZEN)

Knowledge about the extent of nutrient variability in local barley germplasm is an important prerequisite for efficient crop improvement. The present study is one of the first to assess the potential of Tunisian barley populations (named Testour, Gergis, and Enfidha) as sources of desirable traits for barley improvement and for the prevalence of Fusarium species and the mytoxin zearalenone (ZEN). Analysis of variance revealed highly significant differences between barley populations for nutrients density. The lowest phytate/zinc molar ratios were observed in Testour and Enfidha populations with 7.23 and 9.97, respectively. However, the bioavailability of iron of most barley populations (95.4%) was inhibited mainly by the high phytate content. Oleic acid (15.2–18.7%), linoleic acid (13.8–16.01%), and palmitoleic acid (4.7–14.2%) were identified as predominant fatty acid constituents in all three barley populations. Based on morphologic and molecular characterization, Fusarium graminearum and Fusarium culmorum were the predominant species that infected Testour, Gergis, and Enfidha populations. The concentration of zearalenone ranged between 0 and 140 µg kg−1. The highest levels of zearalenone, 92 μg kg−1 and 60 μg kg−1, were detected in Testour populations that were infected with F. graminearum and F. culmorum, respectively. These relatively low amounts of zearalenone in barley populations can be attributed to the Tunisian climate and the resistance of local genotypes. Testour and Enfidha barley populations could potentially be used to improve breeding programs for biofortification.

The Efficiency of Different Priming Agents for Improving Germination and Early Seedling Growth of Local Tunisian Barley under Salinity Stress.

The current work aimed to investigate the effect of seed priming with different agents (CaCl2, KCl, and KNO3) on germination and seedling establishment in seeds of the barley species of both Hordeum vulgare (L. Manel) and Hordeum maritimum germinated with three salt concentrations (0, 100, and 200 mM NaCl). The results showed that under unprimed conditions, salt stress significantly reduced the final germination rate, the mean daily germination, and the seedling length and dry weight. It led to a decrease in the essential nutrient content (iron, calcium, magnesium, and potassium) against an increase in sodium level in both of the barley species. Moreover, this environmental constraint provoked a membrane injury caused by a considerable increase in electrolyte leakage and the malondialdehyde content (MDA). Data analysis proved that seed priming with CaCl2, KCl, and KNO3 was an effective method for alleviating barley seed germination caused by salt stress to varying degrees. Different priming treatments clearly stimulated germination parameters and the essential nutrient concentration, in addition to increasing the seedling growth rate. The application of seed priming reduced the accumulation of sodium ions and mitigated the oxidative stress of seeds caused by salt. This mitigation was traduced by the maintenance of low levels of MDA and electrolyte leakage. We conclude that the priming agents can be classed into three ranges based on their efficacy on the different parameters analyzed; CaCl2 was placed in the first range, followed closely by KNO3, while the least effective was KCl, which placed in the third range.

Proteomic analysis of salt-responsive proteins in the leaves of two contrasting Tunisian barley landraces

Proteomic analysis of salt-responsive proteins in the leaves of two contrasting Tunisian barley landraces

Allelic variations at the HvSNF2 and HvBM5 loci are associated with the heading date and growth habit of barley (Hordeum vulgare L.) under a semi-arid climate

The heading date and growth habit are key factors that regulate the transition from the vegetative to the reproductive stage in barley. In this study, we used PCR based markers to identify the allelic variations in the Vrn-H1 (HvMB5) and Vrn-H2 (HvSNF2) genes and to predict the heading date and growth habit of a collection of Tunisian barley assessed under a semi-arid climate. The allelic variation at HvBM5 revealed two PCR fragments at 830 and 344 bp. Primer sets used to amplify the HvSNF2 gene have resulted in different alleles size of 543, 623, and 700 bp. Different allelic combinations of HVBM5 and HvSNF2 were associated with the heading date and growth habit. The spring and early heading accessions were only characterised by the amplification of the HvSNF2 fragment at 700 bp. All the winter accessions yielded the PCR product HvBM5 at 830 bp, but the variation in the heading date was determined by the HvSNF2 alleles. These DNA markers will be a powerful tool to predict the heading date and growth habit and can be used as markers for the assisted selection to speed up the national breeding programme.

Genotype by Environment Interactions for Yield-Related Traits in Tunisian Barley (Hordeum vulgare L.) Accessions Under a Semiarid Climate

Genotype by environment interaction and stability analyses are among the most important evaluations conducted in plant breeding. In this study, we evaluated the yield-related traits of 32 Tunisian barley (<em>Hordeum vulgare </em>L.) accessions over three consecutive cropping seasons in a semi-arid environment. Phenotypic analysis identified heading date and spike length as the two major traits contributing most to the total phenotypic variation under a semiarid climate. Hierarchical clustering grouped the 32 accessions into four groups. Although the effect of the interaction between genotype and environment was important for yield (48%), it had comparatively little influence on heading date (9.9%) and plant height (8.14%). Stability analysis identified the djebali accession, with the smallest coefficient of variability, as a stable genotype across the three assessed environments. Overall, based on the higher yield and small coefficient of variance, we selected 11 promising genotypes. In addition, varieties developed by the Tunisian breeding program were found to show high mean yield, stability across all environments, and greater adaptability. Accessions with superior adaptation and stability will be introduced into the national breeding program for further evaluation and characterization.

Assessment of Genetic Diversity and Population Structure of Tunisian Barley Accessions (Hordeum vulgare L.) Using SSR Markers

In barley breeding programs, information about genetic dissimilarity and population structure is very important for genetic diversity conservation and new cultivar development. This study aimed to evaluate the genetic variation in Tunisian barley accessions (<em>Hordeum</em><em> </em><em>vulgare </em>L.) based on simple sequence repeat (SSR). A total of 89 alleles were detected at 26 SSR loci. The allele number per locus ranged from two to five, with an average of 3.4 alleles per locus detected from 32 barley accessions, and the average value of polymorphic information content was 0.45. A cluster analysis based on genetic similarity was performed, and the 32 barley resources were classified into five groups. Principal coordinates (PCoA) explained 12.5% and 9.3% of the total variation, and the PCoA was largely consistent with the results of cluster separation of STRUCTURE software analysis. The analysis of genetic diversity in barley collection will facilitate cultivar development and effective use of genetic resources.

Changes in phytase activity, phosphorus and phytate contents during grain germination of barley (Hordeum vulgare L.) cultivars

Phytase activity, phosphorus and phytate contents in hydroponic fodder (up to 12 days of grain germination) of four Tunisian barley (Hordeum vulgare L.) cultivars (Arbi, Ardhaoui, Souihli, and Rihane) were studied. Barley cultivars differed significantly in their phytase activity (0.6–1.6 U/g), phosphorus (3.2–5.0 mg/g DM) and phytate (4.2–4.7 mg/g DM) contents. Phytase increased significantly up to 8 days of germination and decreased steadily thereafter. The phytase activity after 8 days of germination was increased up to tenfold in Arbi and Ardhaoui cultivars, eightfold in Souihli and fivefold in Rihane. The increase in phytase activity during germination was accompanied by a significant decrease in phytate content for all barley cultivars (reduced by 92–97%). The decrease in phytate content of sprouted barley by germination should improve phosphorus availability of the grain. Based on their phytase activity and phosphorus contents before germination, barley cultivars are ranked as Rihane > Ardhaoui > Souihli > Arbi. However, after germinating for 12 days the differences among varieties in phytase activity, phytate and phosphorus contents became non-significant. Further research is warranted to highlight the effect of germination on other nutritional attributes of hydroponic sprouted barley and its suitability as a feedstuff for farm animals.

Assessment water productivity of barley varieties under water stress by AquaCrop model

Drought is the major a biotic stress that reduces plant growth and crop productivity worldwide. AquaCrop model is one of the most widely used simulation models, which simulates the growth, yield and water productivity of the crops. Field experiment was carried out in the Experimental Research Station of Nubaria, during two seasons of 2016/2017 and 2017/2018. The study to assess water productivity of Mediterranean barley (Egyptian, Tunisian, Algerian and Morocco) varieties grown under water stress condition (40% of water holding capacity) compared to normal one (75% of water holding capacity) by AquaCrop model. Deviations (%) between observed under normal irrigation water and observed water deficit (stress), AquaCrop model normal and AquaCrop model stress, data obtained were (2.36, 1.84, 2.25 and 1.59%) for Egyptian barley varieties, respectively. For Tunisian barley varieties, deviations (%) were (2.06, 1.59, 2.78 and 3.62%), respectively. For Algerian barley varieties, were (2.12, 1.66, 2.88 and 3.71%), respectively. The percentage of absolute difference between the percentage of variation in the case of water stress and the case without water stress treatment was 5.36% under Egyptian varieties, followed by Morocco varieties (12.78%). Egyptian varieties are the least tolerant of water stress treatment where the percentage difference in the absolute difference between the cases is equal to 25%.

Distribution, population dynamics and damage potential of barley stem gall midge, Mayetiola hordei (Diptera: Cecidomyiidae) on cultivated barley in two semi-arid areas of North Tunisia

Barley stem gall midge, Mayetiola hordei (Kieffer) (Diptera: Cecidomyiidae) is among the most destructive pests of barley (Hordeum vulgare L.) in the Mediterranean region of southern Europe and northern Africa. In Tunisia, the biology and ecology of this pest are not well documented. In addition to a management study, a study of M. hordei distribution, frequency of occurrence and population dynamics in barley crops was conducted in two semi-arid regions of North Tunisia. The pest was detected in 84% of all sampled fields across two years. Zaghouan region was identified as a high spot region with economic infestations registered in 67 and 56% of surveyed fields in 2013 and 2014, respectively. Three annual generations occurred at both sites, with two complete and one incomplete generation. The second generation (winter generation) is the most important one in terms of crop damage. The study showed that damage from this pest affects host plant growth at different developmental stages. The highest infestation was observed during tillering and elongation. The impact of different sowing date of barley on M. hordei infestation was also conducted. The infestation rate of barley by M. hordei increased by delaying sowing date. We demonstrate that M. hordei is a serious biosecurity threat to Tunisian barley's production and industry.

Identification and characterization of phenolic compounds extracted from barley husks by LC-MS and antioxidant activity in vitro

Phenolic compounds were extracted from Tunisian barley husks obtained through a pearling process, by using two different extraction solvents: acid treatment with sulfuric acid and alkaline delignification with sodium hydroxide. Their antioxidant properties in vitro were investigated using 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging test and butylated hydroxyanisole (BHA). Antioxidants composition was evaluated with LC-MS analysis. Results suggest that the best yield of crude extracts with high level of phenolic compounds exhibiting strong antioxidant activities were found after pre-hydrolysis and delignification step of barley husks. The lowest average total phenolic content found was 763.665 mg/100 g, presenting an EC50 value of 0.93 g/L, four higher antioxidant levels than BHA (0.24 g/L). All extracted fractions showed high contents of p-coumaric acid (≥491.189 mg/100 g), trans-ferulic acid (≥501.475 mg/100 g) and syringic acid (≥192.228 mg/100 g). These results contribute to enhancing the value of barley husks as a good source of natural antioxidants, which serve as new functional food ingredients and dietary supplements.

Variable Levels of Tolerance to Water Stress (Drought) and Associated Biochemical Markers in Tunisian Barley Landraces.

Due to its high tolerance to abiotic stress, barley (Hordeum vulgare) is cultivated in many arid areas of the world. In the present study, we evaluate the tolerance to water stress (drought) in nine accessions of “Ardhaoui” barley landraces from different regions of Tunisia. The genetic diversity of the accessions is evaluated with six SSR markers. Seedlings from the nine accessions are subjected to water stress by completely stopping irrigation for three weeks. A high genetic diversity is detected among the nine accessions, with no relationships between genetic distance and geographical or ecogeographical zone. The analysis of growth parameters and biochemical markers in the water stress-treated plants in comparison to their respective controls indicated great variability among the studied accessions. Accession 2, from El May Island, displayed high tolerance to drought. Increased amounts of proline in water-stressed plants could not be correlated with a better response to drought, as the most tolerant accessions contained lower levels of this osmolyte. A good correlation was established between the reduction of growth and degradation of chlorophylls and increased levels of malondialdehyde and total phenolics. These biochemical markers may be useful for identifying drought tolerant materials in barley.

Fingerprinting and genetic purity assessment of F1 barley hybrids and their salt-tolerant parental lines using nSSR molecular markers.

Hybridity and the genuineness of hybrids are prominent characteristics for quality control of seeds and thereby for varietal improvement. In the current study, the cross between two local barley genotypes (Ardhaoui: female; Testour: male) previously identified as susceptible/tolerant to salt stress in Tunisia was achieved. The hybrid genetic purity of the generated F1 putative hybrids and the fingerprinting of the parents along with their offspring were assessed using a set of 17 nuclear SSR markers. Among the analyzed loci, 11 nSSR were shown polymorphic among the parents and their offspring. Based on the applied 11 polymorphic SSR loci, a total of 28 alleles were detected with an average of 2.54 alleles per locus. The locus HVM33 presented the highest number of alleles. The highest polymorphism information content value was detected for the locus HVM33 (0.6713) whereas the lowest PIC value (0.368) was revealed by the loci BMAC0156, EBMAC0970 and BMAG0013 with a mean value of 0.4619. The probabilities of identical genotypes PI for the 11 microsatellite markers were 8.63×10-7. Banding patterns among parents and hybrids showed polymorphic fragments. The 11 SSR loci had produced unique fingerprints for each analyzed genotype and segregate between the two parental lines and their four hybrids. Parentage analysis confirms the hybrid purity of the four analyzed genotypes. Six Tunisian barley accessions were used as an outgroup in the multivariate analysis to confirm the efficiency of the employed 11 nSSR markers in genetic differentiation among various barley germplasms. Thus, neighbor joining and factorial analysis revealed clearly the discrimination among the parental lines, the four hybrids and the outgroup accessions. Out of the detected polymorphic 11 nuclear SSR markers, a set of five markers (HVM33, WMC1E8, BMAC0154, BMAC0040 and BMAG0007) were shown to be sufficient and informative enough to discriminate among the six genotypes representing the two parental lines and the four hybrids from each others. These five nSSR markers presented the highest number of alleles per locus (An), expected heterozygosity (He), PIC values and the lowest probabilities of identity (PI). These nSSR loci may be used as referral SSR markers for unambiguous discrimination and genetic purity assessment in barley breeding programs.

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

ABSTRACTIn 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’s correlation test revealed significant correlations between the antioxidant activities of barley extracts and both hydroferuloyl glucose and catechin-3-glucose.

Low Genetic Differentiation and Evidence of Gene Flow among Barley Landrace Populations in Tunisia

Tunisian barley (Hordeum vulgare L.) landraces, representing the oldest cultivated accessions, are growing in scattered populations across drought‐ and salt‐stressed environments and constitute a precious reservoir of potentially useful traits for breeding programs. The objective of this study was to elucidate genetic diversity and population structure of barley landraces across the landscape of Tunisia. Populations from 11 geographic zones were genotyped using 21 nuclear microsatellites. A high level of genetic polymorphism with 170 detected alleles was recorded among the studied genotypes. The average allelic richness was 8.095 alleles per locus. The index of genetic diversity (He) showed an average of 0.741. Genetic diversity was very high within populations, whereas differences among populations were difficult to detect. Only 0.15% of the DNA variation was apportioned among landraces (P < 0.001), whereas 99.85% of the DNA variation was maintained within these landraces. A high gene flow (Nm) was revealed among the investigated populations, which has been facilitated by exchange of barley seeds between Tunisian cereal farmers of different regions. Genetic diversity within Tunisian barley landrace germplasms may help to maintain adaptation to a broad range of environmental conditions and provide genetically diverse resources for barley breeders. Both ex situ (seed banks) and in situ (on‐farm) conservation strategies may be required to maintain barley landrace genetic resources.

Introgression of barley yellow dwarf virus resistance into Tunisian barley varieties

The original objective of cross breeding was to develop high-yielding spring barley with high barley yellow dwarf virus resistance. Imen is an F5-derived line with the original experimental number 137. A single seed selection breeding method was used to develop the cultivar. Imen is well adapted to semi-arid areas, carrying the resistant gene Yd2.

BIOCHEMICAL COMPOSITION AND NUTRITIONAL EVALUATION OF BARLEY RIHANE (HORDEUM VULGARE L.).

Background:Many experimental studies have suggested an important role for barley Rihane(BR)in the prevention of colon cancer and cardiovascular diseases. The objective of this study was to evaluate the physico-chemical properties and nutritional characterizations of BR compared to other varieties grown in Tunisia (Manel, Roho and Tej).Material and Methods:Total, insoluble and soluble dietary fiber(β-glucan), total protein, ash and some minerals of BR and Tunisian barley varieties were determined.Results:The results revealed that BR is good source of dietary fiber mainly β-glucan compared to the other varieties. This variety is a relatively rich source of phosphorous and potassium and it contains many important unsaturated fatty acids. BR has higher nutritional value than other varieties.Conclusion:Barley Rihane has significant nutritional characterizations compared to others Tunisian barleys varieties.Abbreviations: BR, Barley Rihane; LDL, low density lipoprotein; HDL, high density lipoprotein; AOM, azoxymethane; TBV, Tunisian barley varieties; TGW, thousand grain weight; SW, weight specific; TDF, total dietary fiber; IDF, insoluble dietary fiber; SDF, soluble dietary fiber; DM, Dry Matter.

Incorporation of β-Glucans into Pasta Extracted from Two Tunisian Barley Cultivars

Abstract The main objective of this study is to extract water-soluble barley (1→3) and (1→4)-β-d-glucans (β-glucans) from milled seeds of two common Tunisian barley cultivars (Manel and Rihane). A mixture of these barley β-glucans was added to spaghetti made with semolina of durum wheat. Cooking quality related traits of functional spaghetti made with durum wheat semolina was investigated. Four spaghetti samples prepared from semolina added with β-glucan ratios: 1, 3, 5 and 7 g/100 g; were developed and compared to the check. Samples were assessed for water absorption, optimal cooking time, cooking loss, swelling index, colour, carotenoids pigments, hardness, moisture, proteins and ash content. Results indicated that spaghetti added with Tunisian barley β-glucans have a good brightness and acceptable general aspect compared to the check. Spaghetti samples showed lower moisture and proteins contents and higher mineral contents and cooking loss. Lower swelling index and hardness properties were noted in incorporated pasta.