Tunisian Barley Research Articles

Identification of barley landrace genotypes with contrasting salinity tolerance at vegetative growth stage.

In the present study, we evaluated the behavior of 21 Tunisian barley landraces under salt stress. The evaluation was performed using 14 morphological and physiological traits at vegetative growth stage under severe salt stress (200 and 250 mM). A multivariate analysis was used in order to select the genotypes with contrasting behavior towards salinity and to identify the major traits conferring salinity tolerance. According to the PCA analyses the genotypes exhibited diverse behavior with the salt stress concentration, indeed 3 different clustering profiles were obtained. Eleven quantitative characters were considered the most pertinent for the ranking of genotypes for salt tolerance. Among them the total fresh weight and the net CO2 assimilation rate were the most discriminating descriptors at 250 mM NaCl. These parameters allowed as the identification of the contrasting pair genotypes toward salinity. "Testour" was classified as the most sensitive and "Enfidha" the most tolerant toward salinity stress. These findings would be of great relevance in breeding programs.

Evaluation of the allelopathic potential of water-soluble compounds of barley (Hordeum vulgare L. subsp. vulgare) and great brome (Bromus diandrus Roth.) using a modified bioassay

Description of the subject. The present study focuses on the description of the allelopathic interactions between wild and crop species that may occur in a given ecosystem. Objectives. The objective is the evaluation of the allo- and autoinhibition activity of root exudates of barley (Hordeum vulgare L. subsp. vulgare) and great brome (Bromus diandrus Roth.) seedlings by water-soluble allelochemicals. Method. The allelopathic activities of five Tunisian barley genotypes (modern varieties and landraces), one Saudi Arabian barley landrace and great brome were assessed using a modified laboratory bioassay named “seedling-after-seedling agar method”. Results. The barley or the great brome reduced, to a greater extent, the root growth compared to the shoot growth of receiver species. The response of the root system architecture of the great brome towards barley root exudates was studied in detail. All the measured root traits were highly sensitive to the presence of barley. In our conditions, the allelopathic activity of barley root exudates had no apparent relationship with the size of the root and a prominent action of genetic determinants in the allelopathic potential between genotypes is proposed. The alloinhibitory activity of barley or great brome root exudates deferred between the receiver species but was always higher than the autoinhibition potential. The autoinhibition in barley proved to depend on whether the genotypes used as donor and receiver are identical or different, suggesting a specific interaction of allelochemicals with the receiver plant. These molecules seem to be the main actors in the allelopathic barley potential as external factors such variations of pH have no evident relevance in the inhibition process. Conclusions. Barley and great brome exude molecules in their surroundings. This affects the growth of the receiver plants, suggesting that these compounds might contribute to the plant community dynamics.

Comparative Study of Salinity Effect on Some Tunisian Barley Cultivars at Germination and Early Seedling Growth Stages

In the present study we investigate the effect of two NaCl concentrations (100 and 200 mM) on the germination, growth (dry weight production, leaf area, water content) and physiology (ion content, proline and soluble sugar concentrations), chlorophyll content and fluorescence of three Tunisian barely cultivars: Rihane, Kounouz and Lemsi. Seeds were germinated and grown in Petri dishes on filter paper with solution of the respective treatment, then carried and grown out in pots under semi-controlled conditions. The barley cultivars were grown with 3 different treatments NaCl 0 mM as control, 100 mM and 200 mM of NaCl, added to the Hoagland’s nutrient solution. Salt stress decreased, daily germination, dry weight, leaf area, leaf water content and K+ contents in all varieties. Indeed, as salinity increased, a progressive and a significant increase of proline and Na+ contents were observed. Based on the Germination stress tolerance index (GSI), Kounouz cultivar tolerates the best salinity at germination stage. However, at tillering stage, the Sensitivity index (SI) shows that Rihane is the most tolerant cultivar. Indeed, it accumulates the highest content of proline in leaves as compared with the other cultivars and its accumulation rose with the increasing salt concentration and kept the higher K+/Na+ ratio.

Phytochemical content and antioxidant properties of diverse varieties of whole barley (Hordeum vulgare L.) grown in Tunisia

Four varieties (Rihane, Manel, Roho, and Tej) of Tunisian barley were analysed for their antioxidant activities (AA) using ABTS and DPPH radicals cation, and ferric reducing/antioxidant power (FRAP) methods. The total phenolic (TPC), total flavonoid (TFC) and condensed tannins (CTC) contents were measured. The results indicated that the total phenolic contents ranged from 195.02±0.32 to 220.11±0.32mg gallic acid equivalent/100g fresh weight. Results showed that Rihane has the highest TPC, TFC and CTC compared to other varieties. Roho barley had a lower activity than Tej barley. A significant correlation (p<0.05) was found between TPC, TFC, CTC and AA. This study suggests that Tunisian barley varieties may serve as a good source of natural antioxidants.

The Use of ISSR and RAPD Markers for Genetic Diversity among South Tunisian Barley

Random amplified polymorphic DNA (RAPD) and intersimple sequence repeat (ISSR) were assayed to determine the genetic diversity of 80 barley specimens from South Tunisia. The ISSR primers showed variation in the percentage of polymorphism, band informativeness (Ib), and resolving power (Rp). The percentage of polymorphism is 66.67%, the average Ib ranged from 0.24 to 0.39, while Rp ranged from 0.74 to 1.16. In RAPD analysis, three primers yielded a total of 17 scorable bands, which are all polymorphic. The three polymorphic primers exhibited variation with regard to average band informativeness (AvIb) and resolving power (Rp). RAPD and ISSR marker systems were found to be useful for the genetic diversity among the barley specimens. The two dendrograms obtained through these markers show different clustering of 80 barely specimens, but we noted that some clusters were similar in some cases. A poor correlation () was found between both sets of genetic similarity data, suggesting that both sets of markers revealed unrelated estimates of genetic relationships. Therefore, the ISSR and RAPD molecular markers show two genetic grouping of studied barely specimens.

Deoxynivalenol contamination in Tunisian barley in the 2009 harvest

In Tunisia, barley is commonly used in human consumption in a variety of food forms. In this regard, a high quality of this agricultural product is always demanded by consumers. A survey of the natural occurrence of deoxynivalenol (DON), the most common Fusarium mycotoxin in small grain cereals, in barley harvested in the main cropping regions in Northern Tunisia in the 2009 harvest was conducted. A total of 72 samples were analysed for DON using high-performance liquid chromatography (HPLC) with a UV visible detector set at 220 nm. Between 36% and 100% of the samples were positive for DON with averages ranging from 1.2 to 2.4 mg kg−1. A positive correlation between DON levels and temperature was seen; on the other side no correlation between DON contents and rainfall was observed. In this study we notably showed the effect of regions on DON contamination.

Somatic embryogenesis and organogenesis from mature caryopses of North African barley accession “Kerkena” (Hordeum vulgare L.)

The regeneration ability of a Tunisian barley accession originated from Kerkena islands was monitored through somatic embryogenesis and organogenesis. To prevent or to reduce normal germination, longitudinally bisected as well as base-wounded mature caryopses were cultured on a modified Chee and Pool-based medium (CP) enriched with different phytohormonal combinations. The greatest embryogenesis response was obtained when base-wounded caryopses were cultured on CP enriched with 2 mg/l chlorophenoxyacetic acid + 2.5 mg/l kinetin (76.85%). The same combination coupled to longitudinally bisected caryopses led to the embryogenic induction at the hypocotyl base of the germinated caryopses (61.9%). Embryogenic calluses differentiated into globular, heart-shaped, torpedo, and fully differentiated stages of somatic embryos on hormone-free Murashige and Skoog-based medium. Rooted plantlets were successfully transferred to soil and grown to maturity in the greenhouse and produced fertile seeds within 3 mo. On the other hand, organogenesis was achieved on CP enriched with 2 mg/l 2,4-dichlorophenoxyacetic acid + 2.5 mg/l kinetin. Histological aspects and scanning electron microscopy of both regeneration methods confirmed further the embryogenic and organogenic nature of the established processes. This efficient plant regeneration system provides a foundation for generating transgenic plants and germplasm preservation of “Kerkena” barley accession.

Genotype x environment interactions and heritability of quantitative resistance to net blotch in Tunisian barley

A doubled-haploid barley population derived from a cross between the Tunisian cultivar ‘Roho’ and the local line ‘90’ was used to assess the genotype x environment interaction, heritability estimates and correlations between disease parameters of net blotch resistance at adult growth stage in three environments. Net blotch reaction was evaluated using the mass disease index, the area under the disease progress curve and the apparent infection rate. The DH lines showed different levels of quantitative resistance to Pyrenophora teres under low, moderate and high epidemic conditions. Large variation of the mass disease index, the area under the disease progress curve and the apparent infection rate was obtained under high-pressure conditions that facilitate identifying tolerant lines. Significant genotypic differences were noted, however preponderant genotype x environment interactions were the major sources of variation. Broad sense heritability values were large for all parameters using data from single environment and low for the mass disease index, the area under disease progress curve and the apparent infection rate using estimates from different growing conditions. In a single environment, resistance related parameters were found to be genetically associated. Excepting mass disease index, lack of associations between area under the disease progress curve and apparent infection rate measured on the three field conditions were obtained. The results obtained suggest that loci for mass disease index may be pleiotropic or linked and loci for areas under the disease progress curve and apparent infection rate may be independent. Multi-location screening for quantitative resistance to P. teres should be considered in a breeding program.

Detection of Spontaneous Reciprocal Translocation Lines in Tunisian Barley

Detection of Spontaneous Reciprocal Translocation Lines in Tunisian Barley

Pathotype and microsatellite analyses reveal new sources of resistance to barley scald in Tunisia

We examined the variation and relationships between pathogenicity and a microsatellite-based haplotype in 79 Tunisian Rhynchosporium secalis isolates that were collected from the most commonly cultivated barley populations in Tunisia, Rihane cv. and local landraces, with the goal of finding genes that might be used to monitor resistance to scald. Isolates could be classified into three distinct virulence groups based on artificial inoculation of 19 differential cultivars with known scald resistance genes. The resistance gene BRR2 carried by the Astrix differential cultivar appeared to be the most effective in Tunisia. Pathotypes sampled from the Rihane host were more virulent than those sampled from local barley landraces. Because some differential cultivars that carried the same resistance genes showed different reaction patterns to 48 of the isolates, we postulated that other unknown resistance gene(s) specific to Tunisian isolates may be prevalent and could be used in Tunisian barley breeding programs. Microsatellite fingerprinting allowed the detection of 11 alleles linked to the virulence and pathogenic identification of 52% of the tested isolates. Thus, microsatellite analysis may provide a rapid tool for pathogen detection, without an inoculation step that requires long incubation periods before ultimate disease assessment.

Morphological and molecular variability of some south Tunisian barley accessions

A total of 20 accessions of barley (Hordeum vulgare L.) from arid regions of Tunisia were collected and evaluated ex situ in experimental fields (Medenine, South Tunisia). Morphological traits and molecular marker (Random Amplified polymorphic DNA) were applied to evaluate genetic diversity of these accessions. The study showed the existence of a highly significant phenotypical variability. Some parameters (production of straw and grain yield) appeared as good criteria to differentiate particular accessions. Concerning molecular variability, 49 RAPD bands were used to calculate Jaccard's distance coefficient for cluster analysis using an arithmetic averaging algorithm (UPGMA). The genetic distance of the 20 studied accessions ranged between 0.25–0.68. The analysis of the hierarchical tree shows the presence of four ramifications thus translating great genetic diversity.

Genetic Diversity of Tunisian Barley Accessions Based on Microsatellite Markers

Genetic Diversity of Tunisian Barley Accessions Based on Microsatellite Markers

Effect of Water Deficit on Physiological Behavior of Some Collected Tunisian Barley Ecotypes

Effect of Water Deficit on Physiological Behavior of Some Collected Tunisian Barley Ecotypes

Morpho-Physiological and Molecular Characterization of Some Tunisian Barley Ecotypes

Morpho-Physiological and Molecular Characterization of Some Tunisian Barley Ecotypes

Relationships Between Some Hordein Components and Quality Properties in Two Tunisian Barley Varieties as Influenced by Nitrogen Fertilisation

Two Tunisian barley varieties, Martin and Rihane, differing by their degrees of adaptation to the environmental conditions and grain yield potential, were grown under different levels of nitrogen (N) fertilisation. The effect of nitrogen supply on the hordein components (expressed in mg per albumen) was determined by Nu-PAGE electrophoresis system using the MOBS running buffer and densitometric analysis. Increasing nitrogen fertilisation increased the protein content by increasing the amount of C-hordeins. The sub-fraction BIII of high molecular weight B-hordeins appeared, in the present study, as the best criterion for distinguishing between the two barley varieties genetic adaptation, and its quantification could be recommended for the understanding of the quality properties of the barley response to different environmental conditions particularly nitrogen fertilisation which appears to be the main origin of differences in the protein aggregation mode of different B-hordein sulphur-rich sub-fractions. &amp;nbsp; &amp;nbsp;

Agronomic Characters of Tunisian Barley Germplasm

Agronomic Characters of Tunisian Barley Germplasm