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Le sesame (Sesamum indicum L.), une plante annuelle autofeconde originaire d’Afrique et d’Inde, est tres sensible aux stades de germination et de semis mais moderement tolerant aux stress hydrique et salin. Cette etude menee en serre a pour objectif d’evaluer l’effet de differentes concentrations de NaCl sur la germination des graines et la croissance des semis de treize cultivars africains de sesame provenant du Senegal, du Burkina Faso, du Cameroun et du Soudan. Un dispositif a blocs randomises avec deux facteurs et trois repetitions a ete utilise . Les resultats montrent un effet negatif du gradient de salinite sur les taux de germination, de survie, la biomasse fraiche, la biomasse seche, le diametre au collet et la longueur de la tige. Les cultivars AS09, AS13, AS14, AS15, AS19 et AS25 ont ete moins affectes par la salinite. L’importance de l’effet depressif depend de la concentration de sel et de la variete de cultivar de sesame. 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.

Parmi les microorganismes de la rhizosphere, figurent les Pseudomonas spp fluorescents qui sont des bacteries d’interet agricole (Plant Growth Promoting Rhizobacteria). Ces Pseudomonas pourraient permettre le developpement de certaines plantes des sols sales et jouer ainsi un role important dans la rehabilitation de ces sols au Senegal. Ainsi l’objectif de cette etude est d’evaluer l’effet de differentes concentrations de NaCl sur la croissance de Pseudomonas spp fluorescents. Des prelevements de sol ont ete effectues au niveau de la rhizosphere de trois speculations (oignon, aubergine, tomate) et sur sol nu. Les souches ont ete isolees par la methode des suspensions dilutions, puis ensemencees sur milieu King B. L’identification des isolats a ete effectuee par observation sur table UV. Trois isolats ont ete selectionnes et purifies sur milieu King B pour chaque echantillon de sol. Afin d’evaluer l’effet de la salinite sur ces souches, les concentrations suivantes ont ete appliquees : 0 M ; 0,17 M ; 0,34 M ; 0,51 M ; 0,70 M ; 0,85 M et 1,03 M. Les resultats obtenus apres 72 h d’incubation montrent que les souches se developpent pour des concentrations en NaCl allant de 0 M a 0,51 M. Les concentrations superieures entrainent une reduction du nombre de colonies pour tous les isolats. Il existe un seuil de tolerance au sel pour chaque souche de Pseudomonas . Cependant, les souches isolees de la rhizosphere de plants d’oignon sont plus resistantes au sel par rapport aux isolats des rhizospheres de plants de tomate et d’aubergine. Ces isolats de Pseudomonas pourraient etre utilises dans les sols sales afin d’ameliorer les rendements des cultures. © 2018 International Formulae Group. All rights reserved. Mots cles: Microorganismes, rhizosphere, PGPR, seuil de tolerance, salinite, resistance English Title: Effect of salinity on the density of fluorescent Pseudomonas spp isolates from the rhizosphere of tomato, eggplant and onion plants in Senegal English Abstract Among the microorganisms of the rhizosphere are the fluorescent Pseudomonas spp. which are bacteria of agricultural interest (Plant Growth Promoting Rhizobacteria). These Pseudomonas could allow the development of some plants of salty soils and play an important role in the rehabilitation of these soils in Senegal. Then the objective of this study is to evaluate the effect of different concentrations of NaCl on the growth of fluorescent Pseudomonas spp. So, soil samples were taken from the rhizosphere of three crops (onion, eggplant, tomato) and on bare soil. The strains were isolated by the dilution suspensions method, then seeded on King B medium. The identification of the isolates was performed by observation on a UV table. And three isolates were selected and purified on King B medium for each soil sample. In order to evaluate the effect of salinity on these isolates, the following concentrations were applied: 0 M; 0.17 M; 0.34 M; 0.51 M; 0.70 M; 0.85 M and 1.03 M. The results obtained, after 72 h of incubation, show that the isolates develop for concentrations between 0 and 0.51M. Higher concentrations lead to significant decrease of colony density for all isolates. There is a salt tolerance limits for each Pseudomonas isolate. However, rhizosphere isolates of onion plants are more resistant to salt than isolates from other rhizospheres. These Pseudomonas isolates could be used in salty soils to improve crop yields. © 2018 International Formulae Group. All rights reserved. Keywords: Microorganisms, rhizosphere, PGPR, salinity, tolerance-limit, resistant

International audience; Intraspecific mitochondrial variability was studied in ten strains of A. bisporus var. bisporus, in a strain representative of A. bisporus var. eurotetrasporus and in a strain of the closely related species Agaricus devoniensis. In A. bisporus, the cox1 gene is the richest in group I introns harboring homing endonuclease genes (heg). This study led to identify group I introns as the main source of cox1 gene polymorphism. Among the studied introns, two groups were distinguished according to the heg they contained. One group harbored heg maintained putatively functional. The other group was composed of eroded heg sequences that appeared to evolve toward their elimination. Low nucleotide substitution rates were found in both types of intronic sequences. This feature was also shared by all types of studied mitochondrial sequences, not only intronic but also genic and intergenic ones, when compared with nuclear sequences. Hence, the intraspecific evolution of A. bisporus mitochondrial genome appears characterized by both an important mobility (presence/absence) of large group I introns and by low nt substitution rates. This stringent conservation of mitochondrial sequences, when compared with their nuclear counterparts, appears irrespective of their apparent functionality and contrasts to what is widely accepted in fungal sequence evolution. This strengthens the usefulness of mtDNA sequences to get clues on intraspecific evolution.

Mushrooms collected from different areas in Senegal were molecularly characterized in order to establish phylogenet ic relationships with previously described species. For this, PCR products were analyzed by electrophoresis and sequenced. Orthologous Sequences were deduced by Blastn analy ses from those available in Gen Bank and belonging to clearly identified taxonomic u nits and species. Phylogenetic analyses were performed by the Maximum likelihood method. These analyses led to determine species belonging to three important genera: Agaricus , Ganoderma and Termitomyces. Moreover, phylogenetic analyses have allowed the loc ation of these Senegalese fungal strains in relation with reference species. However, all these Senegalese strains appeared phylognetically distant from the others species and, consequently can be considered as new and still un - described species.

Moesziomyces penicillariae (Brefield) Vanky is a basidiomycete fungus responsible for smut disease on pearl millet, an important staple food in the sub-Sahelian zone. We revisited the life cycle of this fungus. Unlike other Ustilaginales, mating of sporidia was never observed and monoclonal cultures of monokaryotic sporidia were infectious in the absence of mating with compatible partner. These data argued for an atypical monokaryotic diploid cell cycle of M. penicillariae , where teliospores only form solopathogenic sporidia. After inoculation of monoclonal solopathogenic strains on spikelets, the fungus infects the ovaries and induces the folding of the micropilar lips, as observed during early pollination steps. The infected embryo then becomes disorganized and the fungus invades peripheral ovary tissues before sporulating. We evaluated the systemic growth abilities of the fungus. After root inoculation, mycelium was observed around and inside the roots. As argued by transmission electron microscopy (TEM) observations and polymerase chain reaction (PCR) detection using specific primers for M. penicillariae , the fungus can grow from roots to the caulinar meristems. In spite of this systemic growth, no sori were formed on the varieties of pearl millet tested after root inoculation. All together, these data suggest that the reduced life cycle of M. penicillariae – i.e. dispersal of ‘ready to infect’ solopathogenic sporidia, floral infection – is an adaptation to the aetiology of this disease to short-cycle pearl millet varieties from the sub-Sahel.