Microenvironmental conditions drive the differential Cyanobacterial community composition of biocrusts from the Sahara Desert

The Sahara Desert is characterized by extreme environmental conditions, which are a unique challenge for life. Cyanobacteria are key players in the colonization of bare soils and form assemblages with other microorganisms in the top millimetres, establishing biological soil crusts (biocrusts) that cover most soil surfaces in deserts, which have important roles in the functioning of drylands. However, knowledge of biocrusts from these extreme environments is limited. Therefore, to study cyanobacterial community composition in biocrusts from the Sahara Desert, we utilized a combination of methodologies in which taxonomic assignation, for next-generation sequencing of soil samples, was based on phylogenetic analysis (16S rRNA gene) in parallel with morphological identification of cyanobacteria in natural samples and isolates from certain locations. Two close locations that differed in microenvironmental conditions were analysed. One was a dry salt lake (a “chott”), and the other was an extension of sandy, slightly saline soil. Differences in cyanobacterial composition between the sites were found, with a clear dominance of Microcoleus spp. in the less saline site, while the chott presented a high abundance of heterocystous cyanobacteria as well as the filamentous non-heterocystous Pseudophormidium sp. and the unicellular cf. Acaryochloris. The cyanobacteria found in our study area, such as Microcoleus steenstrupii, Microcoleus vaginatus, Scytonema hyalinum, Tolypothrix distorta, and Calothrix sp., are also widely distributed in other geographic locations around the world, where the conditions are less severe. Our results, therefore, indicated that some cyanobacteria can cope with polyextreme conditions, as confirmed by bioassays, and can be considered extremotolerant, being able to live in a wide range of conditions

Analyse des méthodes et de la fiabilité de la prévision des ventes

Supply chain managementDans le contexte économique actuel, les entreprises du monde moderne s’appuyent sur plusieurs leviers pour répondre aux demandes des clients: elles cherchent à développer leurs stratégie commerciale à travers de nouvelles opportunités afin d’accroître leur rentabilité, elles doivent également passer par la réduction des coûts et notamment ceux liées à la chaine logistique. L’objectif étant de mieux satisfaire les besoins des clients, il est donc indispensable de répondre aux exigences d’une qualité de service et au respect du délai de livraison dans un contexte concurrentiel accru, une bonne gestion des stocks est donc la clé de la réussite pour une entreprise. Pour sa prospérité, il est donc primordial d’élaborer une prévision des ventes. L’étude dans ce mémoire permet d’expliquer l’importance d’établir une prévision des ventes fiable; cela passe par plusieurs critères qui sont développés dans les textes issus de recherche scientifique. Nous allons mettre en évidence les solutions et les méthodes appropriées à l’aide de plusieurs éléments tels que l’historique, la saisonnalité, la fréquence de mise à jour etc. La prévision des ventes doit être régulièrement améliorée afin de maintenir sa fiabilité

Effect of sowing dates on the vegetative growth and yield parameters of two quinoa (Chenopodium quinoa Willd.) genotypes

The aim of the present study was to select the best sowing time for two quinoa genotypes (Chenopodium quinoa Willd) grown in Ouargla, located in the Saharan region of Algeria. The adopted experimental device is of the random block type, comparing the effect of three sowing dates in 2018: October 16th, October 31st, and November 15th, on some vegetative growth parameters (number of seedlings raised, total number of plants, total fresh weight of plants, height of plants at panicle stage, number of branches per plant, average weight per plant), and yield parameters (number of panicles per plant, weight of the main panicle, weight of 1000 grains, and total weight of grains per square meter) of two quinoa genotypes: "Q102" Amarilla saccaca and "Giza". The obtained results show that the best sowing date for the "Q102" genotype is the first date (October 16th), which ranked first for most of the parameters studied. On the other hand, the best grain yield was observed by the second sowing date (October 31st). As for the "Giza1" genotype, no yield was observed for the first and second sowing dates, while a very low grain yield was observed only by the third sowing date. The results obtained make it possible to conclude the strong capacity of adaptation of genotype "Q102" to the edapho-climatic conditions of the south of Algeria compared to genotype "Giza1". In fact, this study shows that the production potential of quinoa in the Saharan regions is linked to both the genotype and the sowing date

Yield, growth development and grain characteristics of seven Quinoa (Chenopodium quinoa Willd.) genotypes grown in open-field production systems under hot-arid climatic conditions

Abstract Quinoa is an important Andean crop that can play a strategic role in the development of degraded lands in hot arid regions due to its high nutritional value, genetic diversity and its high adaptability to stressful environments. The aim of this work was to evaluate the agronomic performance (growth development, grain yield and grain quality characteristics) of seven quinoa genotypes (Giza1, Sajama, Santa Maria, Q102, Q29, Q27 and Q18) cultivated under open field conditions in the Sahara Desert of Algeria. Using randomized complete block design (4 blocks), field trials were conducted during two cropping seasons (2017–2018 and 2018–2019) from November to April. The measured parameters included: plant height, number of panicles per plant, 1000-grain weight (TGW), grain yield (GYd), grain protein content (GPt), grain saponin content (GSC), and maturity indicators. The genotype effect was statistically the main source of variation in most parameters investigated as compared to the effect of cropping year. The Q102 genotype produced the highest GYd (2.87 t/ha) and GPt (16.7 g/100 g DM); and it required medium period (149 days) to reach harvest maturity as compared to other genotypes. The genotype Giza1 showed the lowest GYd and also low values for most of traits measured. However, it had the shortest harvest maturity (139 days) and the lowest GSC (0.62 g/100 g DM). The variety Santa Maria recorded the highest TGW (2.68 g), but it took 164 days to reach harvest maturity and it had high GSC (1.92 g/100 g DM). Though the best yield and grain quality characteristics were not reunited in single genotype, our findings showed that quinoa has multi-benefit potentials as a new crop for the arid agriculture in particular in hot-arid regions of North Africa