Soil salinity and drought are among the environmental stresses that most severely affect plant growth and production around the world. In this study the rhizospheres of Salicornia plants and bulk soils were collected from Sebkhet and Chott hypersaline ecosystems in Tunisia. Depiction of bacterial microbiome composition by Denaturing Gradient Gel Electrophoresis unveiled the occurrence of a high bacterial diversity associated with Salicornia root system. A large collection of 475 halophilic and halotolerant bacteria was established from Salicornia rhizosphere and the surrounding bulk soil, and the bacteria were characterized for the resistance to temperature, osmotic and saline stresses, and plant growth promotion (PGP) features. Twenty Halomonas strains showed resistance to a wide set of abiotic stresses and were able to perform different PGP activities in vitro at 5% NaCl, including ammonia and indole-3-acetic acid production, phosphate solubilisation, and potential nitrogen fixation. By using a gfp-labelled strain it was possible to demonstrate that Halomonas is capable of successfully colonising Salicornia roots in the laboratory conditions. Our results indicated that the culturable halophilic/halotolerant bacteria inhabiting salty and arid ecosystems have a potential to contribute to promoting plant growth under the harsh salinity and drought conditions. These halophilic/halotolerant strains could be exploited in biofertilizer formulates to sustain crop production in degraded and arid lands.

Summary Oases are desert‐farming agro‐ecosystems, where date palm (Phoenix dactylifera L.) plays a keystone role in offsetting the effects of drought and maintaining a suitable microclimate for agriculture. At present, abundance, diversity and plant growth promotion (PGP) of date palm root‐associated bacteria remain unknown. Considering the environmental pressure determined by the water scarcity in the desert environments, we hypothesized that bacteria associated with date palm roots improve plant resistance to drought. Here, the ecology of date palm root endophytes from oases in the Tunisian Sahara was studied with emphasis on their capacity to promote growth under drought. Endophytic communities segregated along a north–south gradient in correlation with geo‐climatic parameters. Screening of 120 endophytes indicated that date palm roots select for bacteria with multiple PGP traits. Bacteria rapidly cross‐colonized the root tissues of different species of plants, including the original Tunisian date palm cultivar, Saudi Arabian cultivars and Arabidopsis. Selected endophytes significantly increased the biomass of date palms exposed to repeated drought stress periods during a 9‐month greenhouse experiment. Overall, results indicate that date palm roots shape endophytic communities that are capable to promote plant growth under drought conditions, thereby contributing an essential ecological service to the entire oasis ecosystem.

17Background Aridification is a worldwide serious threat directly affecting agriculture and crop production. In arid

Salinity has an adverse effect on seed germination of several vegetables crops, by creating an osmotic potential outside the seed inhibiting the absorption of water, or by the toxic effect of Na + and Cl - (Khajeh-Hosseini et al. 2003). Osmotic and saline Abstract Background: Salinity affect germination and seedling growth of several crop species, many techniques are used to improve tolerance and development of plants. Priming is an effective technique that improves germination of several vegetables crop under saline condition. That's why, this experiment was carried to study the effect of seed priming with 5 g/L NaCl and KCl on germination and seedlings growth of safflower (Carthamus tinctorius) exposed to five levels of salinity (0, 5, 10, 15 and 20 g/L). Materials and Methods: Safflower seeds were soaked in solutions of NaCl (5 g/L for 12 h) and KCl (5 g/L for 24 h) at 20°C. Primed and non primed seeds were put to germinate in petri dishes and irrigated with saline solutions of five concentrations of NaCl (0, 5, 10, 15 and 20 g/L). Results: NaCl and KCl priming have improved germination parameters (germination percentage, mean germination time, germination index and coefficient of velocity) and growth parameters (radicle and seedling length, seedling fresh and dry weight and Vigour Index) of safflower under saline condition. Conclusions: The present study revealed that, under salt stress, NaCl and KCl priming could be used as a method to improve safflower seed germination. However, further studies are needed to highlight effects of NaCl and KCl seed priming on future growth and development of the culture.