Morphogenetic responses of Populus alba L. under salt stress

The morphogenetic responses to salt stress of TunisianPopu-lus alba clones were studied in order to promote their plantation in dam-aged saline areas. One year-old plants of threeP. alba clones （MA-104, MA-195 and OG） were subjected to progressive salt stress by irrigation during two consecutive years. The plants were grown in a nursery, inside plastic receptacles containing sandy soil and were irrigated with tap water （control） or 3-6 g/l NaCl solution. During this study, leaf epinasty, elongation rate, vigor, internode length, plant architecture, and number of buds were evaluated. Test clone response was highly dependent on the applied treatment and degree of accommodation.The most pronounced alterations were induced under 6g/l of NaCl treatment including leaf epinasty, leaf elongation rate delay, vigor decrease, internode length shortening, and morphogenetic modifications. These responses were less noticeable in the MA-104 clone with respect to the two other clones. The salt effect induced a delay in the leaf elongation rate on the MA-195 and OG clones leading to an early leaf maturity. The vigour and internode length of the MA-104 clone was less affected than the other clones. The OG clone was the most salt-sensitive thus, it developed shorter branches and more buds number than MA-195 and MA-104. The effect of long-term salt stress was to induce early flowering of theP. alba clones which suggests that mechanism of salt accommodation could be developed.

Decline and dieback of cork oak(Quercus suber L.)forests in the Mediterranean basin:a case study of Kroumirie,Northwest Tunisia

Assessing the vulnerability of forest ecosystems in the climate change context is a challenging task as the mechanisms that determine this vulnerability cannot be directly observed.Based on the ecological interrelationships between forests and climate,the present review focused on providing current information about vulnerability assessments of cork oak(Quercus suber L.)forests in the Mediterranean basin,especially,in the Kroumirie region(northwest Tunisia),currently under historic extreme drought conditions.From comparing recent findings in this region,we synthesized data on cork oak decline and mortality collected during the historic drought years 1988–1995 period.Climate change impacts cork forest decline,with special interest shown in elevated temperatures and drought;cork oak forest regeneration,and the adaptation of the Kroumirie forest to climate change,are reviewed herein.The studied region has been influenced largely by frequent prolonged drought periods,especially from 1988 to 1995.Droughts were found to consistently have a more detrimental impact on the growth and mortality rates of cork oak populations.Cork oak mortality was recorded for up to 63,622 trees.In the future,more research studies and observational data will be needed,which could represent an important key to understand ecosystem processes,and to facilitate the development of better models that project climate change impacts and vulnerability.The study is useful for researchers and forestry decision makers to develop the appropriate strategies to restore and protect ecosystems,and to help anticipate potential future droughts and climate change.

Assessing Sprinkler Irrigation Performance Using Field Evaluations at the Medjerda Lower Valley of Tunisia

Irrigation uniformity and wind drift and evaporation losses (WDEL) are major concerns for the design and management of sprinkler irrigation systems under arid or semi-arid conditions. Field trials were carried out to assess irrigation uniformity and WDEL under various wind velocities, sprinkler spacings and operating pressure heads. Based on experimental data, a frequency analysis was performed to infer the occurrence probability of a given uniformity coefficient (UC). In addition, statistical regressions were used to model WDEL as a function of different climatic variables. Increasing the operating pressure head improved uniformity at low wind speeds. It was shown that UC has been severely impaired at wind speeds above 4 m/s. In the prevailing wind conditions, the frequency analysis showed that a sprinkler spacing of 12 m × 12 m provided the best uniformity. In the local conditions, it is recommended to stop irrigation when wind velocity exceeds 4 m/s. Moreover, it was shown that wind speed and relative humidity were the main significant variables influencing WDEL.

Evaluation of Phenotypic Diversity by Use of Variable Analysis Multi of Various Populations of Oak Cork (<i>Quercus suber</i>L.) in Tunisia

Populations of oak cork (Quercus suber L.) originated from different areas in Tunisia were analysed based on morphological characters to assess the overall degree of phenotypic variability, to detect similarities between the genotypes and to evaluate significant forest features. One-way ANOVA analysis shows a significant difference between oak cork populations and demonstrates that parameters measured on leaves show an important degree of variability and permit to discriminate oak cork individuals. Vegetative variables are leaf length, leaf width, petioles length, number of leaf veins, petioles width, spines number, leaf area, length nipples, diameter nipples, weight nipples, and height trees. Diameter trees were scored and subjected to multivariate analysis. Results showed a considerable diversity among local germoplasme of oak cork. Principal component analysis (PCA) revealed that the characters related to the length and width of the sheets and the nipples accounted for a large proportion of the observed variability. Cluster analysis showed a typically continuous phenotypic diversity among oak cork accessions, and little asso-ciations between accessions from same geographic origin. Also, some heterogeneity within accessions that received the same denomination was evidenced. The variability observed between different populations is attached to phenotypic characters which depend primarily on two factors, gene and environment.

Using Clove Essential Oil to Increase the Nutritional Potential of Industrial Fresh Double Cream Cheese

The present study was a potential application of Clove Essential Oil (CEO) in industrial fresh double cream cheese in order to lengthen its conservation and to improve its antioxidant potential. In this work, CEO was extracted by hydro distillation, and then analyzed by GC-MS;24 components of clove essential oil were identified. Eugenol was the major component (57.66%). Its antimicrobial properties against E. coli, Salmonella enteritidis and Staphylococcus aureus, were evaluated by disc diffusion method and minimal inhibitory concentration (MIC). As for, the antioxidant activity of CEO was evaluated by DPPH assay method. An optimum content of CEO (0.37%) was calculated by mixing plan carried out by Expert design software and then added to studied cheese. The responses, fixed from the beginning, for this mixing plan were: minimum inhibitory concentration (MIC), antioxidant activity (IC50), taste and odor intensity and global appreciation. The results found on the cheese supplemented with the optimum content of CEO showed antioxidant activity (IC50 = 0.146) was relatively important compared to conventional cheese (IC50 = 0.477). In fact, the incorporation of CEO in cheese may strongly improve its oxidative stability. Cheese antioxidant activity was not affected during the storage period for 13 days. Results showed also that the fresh double cream cheese could be stored at refrigerated temperature with good taste and odor during the period of 13 days due to antimicrobial properties given by CEO, that suggest lengthening its shelf life.

Integrating multiple electromagnetic data to map spatiotemporal variability of soil salinity in Kairouan region, Central Tunisia

Soil salinization is a major problem affecting soils and threatening agricultural sustainability in arid and semi-arid regions,which makes it necessary to establish an efficient strategy to manage soil salinity and confront economic challenges that arise from it.Saline soil recovery involving drainage of shallow saline groundwater and the removal of soil salts by natural rainfall or by irrigation are good strategies for the reclamation of salty soil.To develop suitable management strategies for salty soil reclamation,it is essential to improve soil salinity assessment pro cess/mechanism and to adopt new approaches and techniques.T his study mapped a recovered area of 7200 m2 to assess and verify variations in soil salinity in space and time in K airouan region in Central Tunisia,taking into account the thickness of soil materials.Two electromagnetic conductivity meters(EM38 and EM31)were used to measure the electrical conductivity of saturated soil-paste extract(ECe)and apparent electrical conductivity(E Ca).Multiple linear regression was established between ECe and ECa,and it was revealed that ECa-EM38 is optimal for E Ce prediction in the surface soils.Salinity maps demonstrated that the spatial structure of soil salinity in the region of interest was relatively unchanged but varied temporally.Variation in salinity at the soil surface was greater than that at a depth.These findings can not only be used to track soil salinity variations and their significance in the field but also help to identify the spatial and temporal features of soil salinity,thus improving the efficiency of soil management.

Using the Markov Chain for the Generation of Monthly Rainfall Series in a Semi-Arid Zone

Numerous methodologies have been developed in the literature for the generation of rain. However, in semi-arid areas where the irregularity of rain is contrasted, the question of the applicability of these models is still relevant. The objective of this article is to propose a development method of stochastic generator of monthly rainfall series. The present work is based on the modeling of the occurrence and the quantity of rain in a separate way. The occurrence is treated in two stages. The first step considers the Markov chain according to the occurrence of annual statements (dry, average and wet). The second step uses the monthly rankings. The amount of rain is calculated based on historical series according to the monthly rank and the annual statement noted. This method is applied to rainfall data recorded at five rainfall stations in semi-arid region of Central Tunisia. The usual and conventional statistical tests of the generated series have shown the validity of this method.

Chemical Composition and Antioxidant Activity of Date Seeds from Different Tunisian Date Palm Cultivars

Chemical composition,polyphenolic and flavonoid contents,and antioxidant activity were determined in date seeds derived from four Tunisian date palm(Phoenix dactylifera)cultivars namely:Goundi,Chekena,Mnekher and Remtha.Sodium and potassium contents in date seeds were determined by flame photometry,phenolic compounds by the Folin-Ciocalteu method,flavonoids by colorimetric quantification,and the antioxidant activity by the DPPH free radical scavenging method.Crude protein content varied widely(p<0.001)between date seed varieties and ranged from 3.95(Goundi)to 7.51%DM(Chekena).No significant differences(p>0.001)were detected between seed varieties for their dry matter(DM)and ash contents.However,sodium,potassium and phosphorus varied widely(p<0.001)between varieties.The highest phenolic content(p<0.001)was observed in Goundi(39.4 mg gallic acid equivalent(GAE)/g DM)and Remtha(36.6 mg GAE/g DM)seed varieties.Likewise,Goundi had the highest(p<0.001)flavonoid content(16.4 mg quercetin equivalent(QE)/g DM)and antioxidant activity(1,807μM Trolox equivalent antioxidant capacity(TEAC)/g DM);however the lowest values(p<0.001)of phenolic(19.2 mg GAE/g DM),flavonoid(8.8 mg QE/g DM)and antioxidant activity(682μM TEAC/g DM)were observed for Chekena seeds.Further studies are needed to verify the potential of date seeds as alternative for animal nutrition.

Diversity of Botryosphaeriaceae species associated with grapevine and other woody hosts in Italy,Algeria and Tunisia,with descriptions of Lasiodiplodia exigua and Lasiodiplodia mediterranea sp.nov

The diversity of Botryosphaeriaceae species associated with“Botryosphaeria dieback”of grapevine was investigated in 18 vineyards in Sardinia,Italy.Lasiodiplodia isolates obtained from different woody hosts including holm oak,sweet orange and broom bush in Italy,Algeria and Tunisia were also characterized.Morphological and cultural characteristics as well as ITS and EF1-αsequence data were used to identify the fungal isolates.Forty-eight botryosphaeriaceous isolates were obtained from 113 symptomatic grapevine samples,from which ten species were identified.Diplodia seriata was the dominant species(25%of isolates),followed by Neofusicoccum parvum(21.7%).Two species,Diplodia olivarum and D.africana are reported for the first time on grapevine.In addition,two new species namely Lasiodiplodia mediterranea sp.nov.from grapevine,holm oak and sweet orange and Lasiodiplodia exigua sp.nov.from broom bush are described.In artificial inoculation experiments conducted on excised green grapevine shoots and lignified canes as well as holm oak seedlings,L.mediterranea was shown to be an aggressive pathogen.