Influence in vitro de divers facteurs abiotiques (température, pH, salinité) sur la croissance mycélienne de trois souches locales de Trichoderma sp.

Les Trichoderma sont des champignons imparfaits saprophytes que l’on retrouve dans divers milieux comme le sol, le bois mort, les débris des végétaux et les organes aériens des plantes. Ils ont un rôle phytoprotecteur et stimulateur du développement des plantes associées. L’effet de différents facteurs abiotiques (température, pH, salinité) sur la croissance mycélienne de trois souches locales de Trichoderma a été évalué. Ces souches ont été isolées à partir de la rhizosphère de la tomate. Une étude préliminaire a été effectuée sur quatre milieux de culture (PDA, MEA, SB et DOX) pour la sélection du milieu d’étude. Les résultats obtenus montrent que le milieu PDA permet une meilleure croissance des souches de Trichoderma. La température optimale de croissance des différentes souches est de 29 °C et le pH 5 se révèle être le plus adéquat pour la culture des Trichoderma. Cette étude montre également que les souches de Trichoderma résistent à des concentrations de sel (NaCl) allant jusqu’à 3%.© 2016 International Formulae Group. All rights reserved.Mots clés: Trichoderma, facteurs limitant, température, pH, salinité, milieu de cultureEnglish Title:  In vitro influence of various abiotic factors (température, pH, salinity) on mycelium growth of three local strains of Trichoderma sp.English AbstractTrichoderma are saprophytic imperfect fungi that are found in various environments such as soil, dead wood, vegetable fragments and plant aerial organs. They protect and stimulate development of related plants. Effects of various abiotic factors (temperature, pH, salinity) on mycelium growth of three local Trichoderma strains were investigated. These strains were isolated from tomato rhizosphere. A preliminary study was performed on four culture media (PDA, MEA, SB and DOX) for the selection of the best media. The results  showed that PDA medium was highly growth of Trichoderma strains. The optimum temperature for growth of different strains is 29 °C and pH 5 was found to be most suitable for Trichoderma culture. Indeed, Trichoderma strains resistant to salt concentrations (NaCl) up to 3%.© 2016 International Formulae Group. All rights reserved.Keywords: Trichoderma, limiting factors, temperature, pH, salinity, culture medi

Germination Stage Screening of Mutants of Cowpea (Vigna unguiculata L. Walp) to Salinity Tolerance

To test the tolerance of cowpea mutants to salinity, cowpea wilds and mutants were subjected to 50, 100, 150, 200, and 250 mM NaCl to test for tolerance to salinity. Genotype and salt concentration interaction were significant. GxS explained mostly the variation observed. More informative salt concentrations were found in 50 mM (99.08) and C100 mM (72.50) against 26.80 in the control environment. High salt concentrations had the lowest germination rates. Seed germination rate of cowpea genotypes decreased from 56.46 to 20.58 with a mean of 36.28 and a variance of 99.08. Despite strong correlations observed between indices, very weak ones were found between AD and STI, -0.02, -0.44, -0.7, -0.79 and -0.84 respectively at salt concentration of 50, 100, 150, 200 and 250. Mouride wild types were most tolerant to salt with a germination rate of 43 % at 50 mM versus 48 and 551 % for respectively Melakh and Yacine. Six (6) mutants were more tolerant to the weakest checks performance which was the 9th best performance

Effet de la salinité sur la germination graines et la croissance des semis de treize cultivars africains de sésame (Sesamum indicum L.)

Le sésame (Sesamum indicum L.), une plante annuelle autoféconde originaire d’Afrique et d’Inde, est très sensible aux stades de germination et de semis mais modérément tolérant aux stress hydrique et salin. Cette étude menée en serre a pour objectif d’évaluer l’effet de différentes concentrations de NaCl sur la germination des graines et la croissance des semis de treize cultivars africains de sésame provenant du Sénégal, du Burkina Faso, du Cameroun et du Soudan. Un dispositif à blocs randomisés avec deux facteurs et trois répétitions a été utilisé . Les résultats montrent un effet négatif du gradient de salinité sur les taux de germination, de survie, la biomasse fraiche, la biomasse sèche, le diamètre au collet et la longueur de la tige. Les cultivars AS09, AS13, AS14, AS15, AS19 et AS25 ont été moins affectés par la salinité. L’importance de l’effet dépressif dépend de la concentration de sel et de la variété de cultivar de sésame. Sesame (Sesamum indicum L.), an annual self-pollinating plant native to Africa and India, is very sensitive to the stages of germination and sowing but moderately tolerant to water and salt stress. The objective of this greenhouse study is to assess the effect of different NaCl concentrations on seed germination and seedling growth of thirteen African sesame cultivars from Senegal, Burkina Faso, Cameroon and Sudan. A randomized block device with two factors and three replicates was used. The results show a negative effect of the salinity gradient on the germination rate, survival, fresh biomass, dry biomass, diameter at the collar and length of the stem. Cultivars AS09, AS13, AS14, AS15, AS19 and AS25 were less affected by salinity. The magnitude of the depressive effect depends on the concentration of salt and the sesame cultivar. &nbsp

Arbuscular Mycorrhizal Fungi Improve Growth and Phosphate Nutrition of <i>Acacia seyal</i> (Delile) under Saline Conditions

Many plant species adapted to semi-arid environments are grown in the Sahelian region in northern Africa. One such species is Acacia seyal (Delile), a multipurpose leguminous tree grown in various agroecological zones, including saline soils. These challenging arid and semi-arid environments harbor a diversity of arbuscular mycorrhizal fungi (AMF) communities that can develop symbiotic associations with plants to improve their hydromineral nutrition. This study compared the effects of native AMF communities isolated from semi-arid sites (high, moderate, and low salinity zones Ndiafate, Ngane, and Bambey, respectively) and the AMF Rhizoglomus aggregatum on the development and phosphate nutrition of A. seyal seedlings subject to three salinity treatments (0, 340, and 680 mM). Plant height, dry matter weight of the shoots and roots, and phosphorus uptake from the soil were measured. Plants inoculated with AMF native species from each site that were provided with up to 340 mM of NaCl had greater shoot height than plants grown under 680 mM salinity. At NaCl concentrations above 340 mM, shoot and root development of A. seyal seedlings diminished. However, dry matter production of shoots (7%) and roots (15%) improved following AMF inoculation compared with the control (respectively 0.020 and 0.07 g for shoots and roots). When inoculated with AMF isolates from the high salinity zone (Ndiafate), phosphate content/nutrition was increased by 10% around 30 days after inoculation compared with non-inoculated seedlings (2.84 mg/kg of substrate). These results demonstrate that native AMF inoculants are capable of helping plants withstand environmental constraints, especially those exposing plants to harsh climatic conditions. We discuss insights on how AMF influences the interplay between soil phosphorus and perceived salinity that may have implications for broader relationships between plants and symbiotic fungi