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Abstract Soil salinity is one of the major environmental stresses affecting crop productivity. Effects of salinity on plants vary widely depending on the developmental stage of the plant as well as types and concentrations of salts. Salinity soil becomes the biggest challengers for human life; about 40% of the world land is threatened with salinization over the world. Multi approaches were urgently needed to get ride of salinity, like selective a new salinity resistant plant grains, continuous reclamation of salt-affected soils, chemical treatments of plants and inoculation of the plants with bio-fertilizer salt-tolerant microorganisms. The present work carried out at Sakha Agricultural Research Station, Kafr El- Sheikh. Therefore, the aim of the present study was to isolate nitrogen fixing cyanobacteria from salty soils and using them to increase rice productivity in saline soil and getting rid of soil salinity. Also studying the role of inoculation with different cyanobacterial inoculants Nostoc calcicola, Anabaena variabilis and Nostoc linkia on rice growth parameters in soil at different concentrations of salinity. Growth parameters had been recorded after 40 days. Twenty nine samples were collected from the upper surface layer of the soil (0-15 cm) from different sites at Kafr El-Sheikh Governorate; to sort and isolate some of the most common cyanobacteria isolates inhabited these rice soils. The 13 isolated cyanobacteria isolates were identified morphologically and physiologically. The propagated cyanobacteria isolates were also tested for their biomass accumulation, nitrogen content and their biochemical composition, i.e., carbohydrates, polysaccharides, Protein, lipids, and pigments content. The obtained results can be summarized as in the following: 5.1. Soil analysis: Soils were collected from different salty sites in (Baltim, Elhamoul, El ryaad and Seidy-Salem) at Kafr El-Sheikh. Soil had different characteristics such as EC, pH, CO3 - -, HCO3 -, Cl -, SO4 - -, Mg++, K+, Na+ and Ca++. Cyanobacteria were isolated from soil showed highly adaption and bear salinity from 4 to 73 dS.m-1. 5.2. Identification of the cyanobacteria isolates: Four nitrogen fixing cyanobacteria were isolated and identified as three isolates were used in study Nostoc calcicola {Baltim ,site (1), Seidy salem, site (6, 7, 8, 13), El hamoul, Site (9)} Anabaena variabilis {(El hamoul, Site (2, 4), El ryad, Site (11)}, Nostoc linkia {(El ryad, Site (3), Seidy salem, Site (10)}, the fourth one was toxic isolate which was identified as Nodularia herveyana (Baltim, Site (12). 5.3. Biomass production by the isolated cyanobacteria strains: All the cyanobacterial isolates grow under the continuous illuminated conditions when they cultured for different periods of 1, 2, 3, 4, 5 and 6 weeks under light intensity of 5000 lux and ambient temperature of 28-32oC on BG11 medium. The data indicated that the highest biomass of 0.949 g.L-1 was recorded by N. calcicola after 5 weeks, followed by N. linkia, which produced 0.680 g.L-1 in the same period. While A. variabilis, recorded high dry weight 0.675 g.L-1 in the fourth weeks. 5.4. Pigments Determination: There was ahighly significant difference between chlorophyll a content of all tested cyanobacteria strains. Results revealed that the highest Chlorophyll a content due to N. Calcicola, and Anabaena variabilis, then Nostoc linkia respectively. Aside chloropylls as the primary photosynthetic pigment, microalgae also form various accessory or secondary pigment, such as phycobiliproteins and awide range of carotenoids. Carotenoid and Phycopilin Pigments, the highest contents were due to Nostoc calcicola. 5.5. Nitrogen content: All the isolated cyanobacteria strains had the ability to produce nitrogen. By increasing the incubation period from 1 to 6 weeks the nitrogen activity increased. The highest nitrogen content was recorded by Nostoc calcicola, followed by Anabaena variabilis, then Nostoc linkia. 5.6. Total carbohydrate content: All the tested isolated cyanobacteria strains on at periods of 1 to 6 weeks led to increase the total carbohydrate contents along with increasing the time of incubation respectively, except in case of Nostoc calcicola, which start decreasing in fifth week, also N. calcicola showed the highest total carbohydrate contents of 29.7% followed by 23.107%, 17.837% recorded by Nostoc linkia and A. variabillis respectively. 5.7. Exopolysaccharides content: Results confirmed that the presence of EPS in the isolated cyanobacteria isolates and showed a highly significant difference between all tested cyanobacteria isolates. Exopolysaccharides content of cyanobacteria isolates increase by increasing the incubation periods. Results revealed that the highest ESP content of 0.198 mg. ml-1 due to N. calcicola in the sixth week followed by Anabaena variabilis, which give 0.183 mg. ml-1 in the fifth week followed by Nostoc linkia, which give ESP content of 0.090 mg. ml-1 in the fifth weeks. 5.8. Total protein contents: The highest TPC, 25.850 mg. g -1 had recorded by Nostoc calcicla, followed by Anabaena variabilis, which gave 17.687 mg. g -1, in the fifth week followed by Nostoc linkia, which gave biomass of 17.190 mg. g -1 in the fifth weeks. 5.9. Effect of filtration of cyanobacterial growth on rice seedlings: Salinity had a highly significant decrease of root length and shoot length of rice seeds. The root length and shoot length (cm) of rice seedlings showed a highly significant reduce with rising salinity concentrations (5, 10, 15, 20, 25 ds. m-1), incase of control (without inculant) and also with inoculation with different cyanobacteria inoculant. Otherwise, inoculation showed a highly significant increase in root length rice seeds compared with un-inoculated. 5.10. Pots experiment: The aim of this experiment was to study the role of inoculation with different cyanobacterial inoculant Nostoc calcicola, Anabaena variabilis and Nostoc linkia on rice growth parameters in soil at different concentrations of salinity. Growth parameters had been recorded after 40 days. The shoot and root length (cm) were highly significant reduced with rising salinity concentrations. Otherwise, inoculation showed a highly significant increase in shoot and root length compared with un-inoculated soils. In addition, inoculation with cyanobacterial isolates (Nostoc calcicola, Anabaena variabilis, and Nostoc linkia). A significant positive effect of inoculation with the tested cyanobacterial isolates in EC was detected. Inoculation decreased the EC of soils compared with (un-inoculated control). It is concluded that: - 1- Cyanobacterial isolates under studying are more efficient in salty soils they had the ability to fix nitrogen. 2- The isolates can biosynthesize and secrete a great diversity of primary and secondary metabolites such as polysaccharides, pigments and carbohydrates which are valuable substances with potential applications in the food, pharmaceutical and cosmetics industries. |