J. BEN YAHMED^1-2*

P. AMIEL²

M. BEN MIMOUN¹

R. MORILLON^2-3

¹ INAT, 43, Avenue Charles Nicolle 1082, Tunis–Mahrajène, Tunisia

² CIRAD, UMR AGAP, Avenue Agropolis, TA A-75/02, 34398 Montpellier cedex 5, France

³ IVIA, Ctra. Moncada-Náquera Km 5, 46113 Moncada, Valencia, Spain

Abstract-Plants are subjected to various abiotic stresses because of environmental conditions which adversely affect their growth and development. Water deficit and salt stress are the main abiotic stresses. These severe environmental stresses may cause dramatic changes at cellular level. Several studies have shown that one of the major physiological damage of the stress at cellular level is related to membranes perturbation leading to ion leakage. Measurements of the dynamics of solute leakage from leaves of different genotypes could thus be used as tool to characterize their properties of tolerance to stress. This work aimed to evaluate the water stress tolerance properties of diploid and tetraploid Citrus as well as Poncirus genotypes using ion leakage method on leaf disc samples. Leaf discs were cut, weighted and immersed in polyethylene glycol (PEG) or salt (NaCl) solutions for 20 hours and were transferred into deionised water to measure ion leakage. The electric conductivity was measured 1h after the introduction of the sample in distilled water and after autoclaving, which leaded to a total ion release and allowed at the end to compare ion leakage rate of the genotypes. For Citrus genotypes, results of ion leakage did not match with the water deficit and salt stress tolerance properties of the same genotypes evaluated in pots. Regarding Poncirus genotype, we were able to show a good correlation between the ion leakage rate of the stressed leaf discs and the two genetic groups we previously revealed by using SSR markers. Also, results of ion leakage matched with water deficit properties of Poncirus genotypes we previously evaluated in pot.

Keywords - ion leakage, conductivity, water deficit, salt stress, diversity.

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H. MEHDI-TOUNSI^1a*

A. CHELLI-CHAABOUNI^2a

D. BOUJNAH ³

M. BOUKRISS¹

¹ Laboratory of Plant Biology, Faculty of Sciences of Sfax, University of Sfax, PB 1171, 3000 Sfax, Tunisia

² National Institute of Agronomic Research of Tunisia, University of Carthage, Ariana, Tunisia

³ Research Laboratory, Improving the productivity of olive tree and product quality, Olive Tree Institute, University of Sousse, PB 14, 4061 Sousse, Tunisia

^a equally contribution.

Abstract-Effects of saline irrigation water were studied on the behaviour of 5-year-old female trees of ‘Mateur’ variety grafted on Pistacia vera L. and Pistacia atlantica Desf. rootstocks for three successive years. Different irrigation water qualities were used: (i) fresh water (ECw: 1.95 dS/m); (ii) moderately saline water (ECw: 5 dS/m); and (iii) saline water (ECw: 12 dS/m). The following parameters were assessed: Individual trunk cross-sectional area, scion shoot growth, stomatal density, leaf area, chlorophylls and water contents. Results showed that scion axillary shoot lengths, internode lengths and bud number decreased significantly at the highest level of saline water treatment mainly in the thrird year of study. Trees grafted on P. atlantica rootstock showed a slight early growth advantage compared to those having P.vera as rootstock. Stomatal density was affected by both salinity and rootstocks. The highest stomata density was obtained with severe saline treatment (ECw: 12 dS/m). During the three years of study, the highest and the lowest stomata density on the abaxial leaf surface were recorded on P. atlantica and P. vera rootstocks, respectively.Leaf chlorophyll content, relative water content and leaf area decreased by increasing salinity. The most important reductions in chlorophyll content, leaf area and relative water content were observed on P.vera rootstock. P. atlantica rootstock induced the lowest decline in chlorophyll content suggesting higher salt tolerance due to the maintenance of higher cell turgor. Agricultural practice based on its use as rootstock may lead to better rusticity of P. vera varieties.

Keywords:pistachio, salinity, rootstocks, growth parameters, chlorophyll content, RWC, leaf area.

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L. Gargouri-Kammoun^1,2

H. Jmii³

B. Essgair³

R. Hajlaoui Mohamed²

N. Sadfi-Zouaoui³

² INRAT, Université de Carthage, Rue Hédi Karray 2049 Ariana, Tunisie.

³ Laboratoire Microorganismes et Biomolécules Actives, Faculté des Sciences de Tunis, Campus Universitaire, 2092 Tunisie.

Abstract-In Tunisia, Maïze is mainly used for the food supply of the cattle in greenery and in silage. The intensification of this cultivation was further developed thanks to the use of hybrid seeds as well as the creation of new irrigated parameters. However, the development of certain fungi in Maïze can affect the grains’ quality by causing mycotoxins’s contamination. The latter are toxic for humans and animals as well, especially in case of a high level of ingestion. Trichothecene is, in fact, a type of mycotoxin produced mainly by Fusarium culmorum and F.pseudograminearum, one of the main factors that lead to maize ear rot. Given that, to fight this disease is difficult and it should be essentially based on the use of fungicides and the conduct of different cultural practices. Therefore, a search for new alternatives strategies based on the microbial antagonism can be explored. The objective of the present paper is to study the growth of bacterial inhibitor of the fungi’s growth, the disease development, as well as the mycotoxins production. A collection of two high-leveled toxine producing strains of Fusarium culmorum and F. pseudograminearum were grown in co-cultivation with Bacillus species. In vitro bio-attempts have demonstrated that Bacillus subtilis has significantly reduced the radial growth of both strains of Fungus. The different in-vivo-attempts were then realized on maize cobs with parallel analysis of the quantification of the trichothecenes deoxynivalenol (DON) type in grain by the ELISA test. These results show the decrease and the deletion of the levels of DON in the grain under study basically due to the opposing bacteria when compared with the specimen.

Keywords: Maïze, deoxynivalenol, Fusarium, Bacillus spp.

Résumé - En Tunisie, la culture du Maïs est destinée principalement à l’alimentation du bétail en verdure et en ensilage. L’intensification de cette culture a été ensuite développée suite à l’utilisation de semences hybrides et à la création de nouveaux paramètres irrigués. Cependant, le développement de certains champignons peut altérer la qualité sanitaire des grains de Maïs par leur contamination par les mycotoxines. Ces dernières peuvent êtres toxiques pour l’homme et les animaux lorsqu’elles atteignent un certain seuil d’ingestion. Parmi ces mycotoxines, figurent les trichothécènes produites principalement par Fusarium culmorum et F. pseudograminearum agents causales de la fusariose de l’épi. Etant donné que la lutte contre cette maladie est difficile et se base essentiellement sur l’emploi des fongicides et des pratiques culturales, la recherche d’autres alternatives de lutte basée sur l’antagonisme microbien peut être explorée. L’objectif du présent travail, est la recherche de bactéries antagonistes capables d’inhiber la croissance du pathogène, le développement de la maladie et la production de mycotoxines. Pour se faire, une collection de F.culmorum et de F.pseudograminearum possédant un pouvoir toxinogène élevé ont été mis en co-culture avec des bactéries du sol du genre Bacillus. A la lumière des bio-essais réalisés in vitro, des souches de Bacillus subtilis ont inhibé significativement la croissance radiale des deux champignons. Des essais in vivo ont été ensuite réalisés sur des épis de Maïs, complétés par une analyse et une quantification des trichothèces de type déoxynivalénol (DON) dans les grains moyennant le test ELISA. Ces résultats montrent la diminution et la suppression de la production des DON dans grains traités par les bactéries antagonistes comparés au témoin inoculé par l'agent pathogène seul.

Mots clés: Maïs, deoxynivalenol, Fusarium, Bacillus spp.

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E. MESSAOUDI¹*

M.T.S GHAIER²

H. AICHI³

M.F. BEJI⁴

L. ZAIBET⁵

¹ Institut National de Agronomisue de Tunisie

² Institut National de Recherche en Géni Rural, Eaux et Forêt

³ Ecole Supérieur de l’Agriculture de Mograne

⁴ Ecole Supérieur de l’Agriculture de Mograne

Abstract-The region of Sidi Thabet is known for its socio-economic problems of farmers. In order to understand the problems of rural development in this region, we aims to analyze the technical efficiency and its determinants to 64 farms in the irrigated area to reveal a general inefficiency of resource use and importance irrigation in the production process.

Keywords: technical efficiency, inefficiency, determinants of efficiency

Résumé - La région de Sidi Thabet est marquée par des problèmes socio économique des agriculteurs. Dans le but de comprendre la problématique de développement rural de cette région, nous avons fait une analyse de l’efficacité technique et ses déterminants pour 64 exploitations agricoles du périmètre irrigué pour révéler une inefficience générale de l’usage des ressources et de l’importance de l’irrigation dans le processus de production.

Mots clés: Efficacité technique, inefficience, déterminants de l’efficacité

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I. BETTAIEB REBEY

F. Z. RAHALI

M. SAIDANI TOUNSI

B. MARZOUK

R. KSOURI

Laboratoire des Plantes Aromatiques et Médicinales, Centre de Biotechnologie de Borj-Cédria, BP 901, 2050 Hammam-Lif, Tunisie

Abstract-Salinity is a severe problem in the entire world and constitutes a serious constraint for crop production; salinity can affect growth, plant production and several aspects of their metabolism, including that of lipids and secondary metabolisms. In this context, this research was, therefore, conducted to determine the effects of salinity on growth, fatty acid and essential oil composition of sweet fennel (Foeniculum vulgarae Mill.) seeds. Plants were treated with different levels of salt stress: 0, 25, 50 and 75 mmol of NaCl. Plant growth was significantly reduced with severity of stress. This last caused also important reductions of the seed yield and yield components. NaCl treatments decreased significantly seed oil content and modified fatty acid composition, particularly the petroselinic acid which the proportion diminished in accordance to the degree of stress. This decrease was accompanied by a concomitant increase of palmitic acid proportion. Besides, NaCl enhances essential oil production in Foeniculum vulgare and induced marked changes on the essentialoil quality. Major changes observed in the essential oil composition were due to the relative proportions of constituents and not to the presence of new or the absence of particular ones. Thus, Tunisian F. vulgare seeds cultivated under NaCl salinity may provide a potential source of volatile substances.

Keywords: Foeniculum vulgare Mill, salinity; yield; fatty acid; essential oil

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S. BACCARI^1*

A. CHAARI RKHIS²

A. CHELLI CHAABOUNI³

M. MAALEJ¹

F. BEN ABDALLAH¹

¹ Faculty of Sciences of Sfax, Tunisia

² Olive Tree Institute Sfax, Tunisia

³ National Institute of Agronomic Research of Tunisia

Abstract-The identification of drought-tolerant rootstocks has become an urgent requirement to overcome the limited availability and poor quality of water .The aim of this study was to select through in vitro conditions drought-tolerant olive seedlings based on growth parameters. Five-month-old olive seedlings (cv. ‘Chetoui’) were subjected to in vitro osmotic stress induced by polyethylene glycol (PEG 4000) during 3 months followed by a rehydration phase during the same period. The liquid nutrient medium (MS) was added with 0, 40 and 80 g/l PEG. Results indicated that mortality rates were markedly increased at 80 g/l PEG. Shoot length, numbers of nodes, axillary shoots and leaves were significantly reduced under water stress. On the other hand, fresh and dry weights of the aerial part and roots were not affected by PEG. During 90 days of rehydration, the mortality rates continue to increase significantly in olive cultivar. However, a partial recovery of axillary shoots was recorded and the aerial part dry weight of tolerant seedlings treated with 40 g/l PEG returned to control level. The aerial part fresh weight of sensitive seedlings showed a significant decrease with respect to the control plants. The percentage of selected tolerant seedlings was 11.4 % and 5.4 %, respectively at 40 and 80 g/l PEG. Therefore, growth parameters may be a good marker for the selection of drought-tolerant seedlings.

Keywords: drought tolerance, growth, olive, selection

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