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Salinity is a major threat to crop production and global food security. Algae and their extracts containing bioactive compounds can enhance the salt tolerance of plants, including the salt-sensitive plants. The current study evaluated the efficacy of Dunaliella salina (Dunal) Teodoresco culture and/or its β-carotene extract in improving the salt tolerance of squash (Cucurbita pepo L. cv. Mabrouka). Amendment of C. pepo with D. salina culture and/or its β-carotene extract was more effective in alleviating the impact of moderate salinity imposed by seawater dilution of 2.5 dS m−1 than either low (0.55 dS m−1) or high (3.5 dS m−1) salinity, with a comparable effect to that of salicylic acid (SA). Plants that received a combination of D. salina culture and its β-carotene extract showed significantly higher growth (total biomass, fruit productivity) and physiological attributes (photosynthetic pigments, nitrogen (N), phosphorus (P), and potassium (K+) contents) than those receiving either amendment alone, reaching up to 80–90% of the SA-treated plants at moderate salinity (2.5 dS m−1). The combination could enhance the antioxidant activity of moderately salt-stressed C. pepo via increasing carotenoids and phenolics contents, suggesting that this combination could enhance the adaptation of C. pepo to the moderate salinity. The present study recommends using the blooms of D. salina and its β-carotene that is naturally secreted in situ in natural or synthetic open systems in improving the salt tolerance of C. pepo instead of using the expensive synthetic hormones.

Aims: Evaluation if foliar spray of destructed cells of Spirulina platensis along with urea fertilizer can contribute to cotton (Gossypium barbadense L. cultivar Giza-94) plant growth, contents of photosynthetic pigments, seed cotton yield, seed index, earliness, lint percent, fineness (Micronair) and strength (Pressely). Study Design: Application of ascending rates of N fertilizer in 3 mainplot treatments and foliar spray with destructed cells of Spirulina platensis in 4 subplot treatments (Contained a non-treated control), with 3 replications. Place and Duration of Study: The Departments of Microbiology and Cotton Research, Sakha Agricultural Research Station, Kafr Elsheikh, Egypt (31º18′30″N & 30º48′14″E) during the two cotton cultivation seasons of years 2016 and 2017. Methodology: Urea (46% N) at 96, 144 or 192 kg N/ha was applied in two equal doses as main-plot treatments. Spirulina platensis was grown and total proteins, contents of 16 amino acids and Fe, K, Mn and P of dried destructed cells were determined and used for foliar application in the rates of 6, 12 or 18 g cells/ha, used as sub-plot treatments. Area of each replicated sub-plot was 12.5 m2. Calcium super phosphate (15% P2O5), potassium sulphate (48% K2O) and Insecticides (when necessary) were supplemented as common treatments. Results: Application of destructed Spirulina increased the plant leaf area, chlorophyll a, b, carotenoids and gibberellin contents, plant height, fruiting branches, open bolls/plant, seed cotton yield and seed index after ginning, fiber length, fineness (Micronair) and strength (Pressely) comparing to the corresponding non-sprayed plants. Urea at 192 kg N/ha along with destructed Spirulina exhibited superiority as enhancers of plant growth, yield and fiber qualities. Conclusion: The dual N/Spirulina combination expressed enhanced cotton growth, yield and qualities of fibers. The tested fertilization strategy is promising for enhanced cotton production economy.

This study investigated the effect of foliar application of extract and culture of Nostoc calcicola and Nostoc linckia on the Fusarium oxysporum f. sp. lycopersici (FOL) that infects tomatoes (Solanum lycopersicum) plant in vitro and in vivo. Cyanobacterial isolates were isolated from saline soils at El-Hamoul and Seidy Salem locations Kafr Elsheikh, Egypt, and identified to be N. calcicola and N. linckia Bioactive compounds of extract were analyzed by Gas chromatography-mass spectrometry (GC-MS). Dry weight, carotene, chlorophyll content, and total phenolic compounds of isolates were measured. Plant height, dry weight, fruit number, and fruit weight of tomatoes were estimated. GC/MS analysis showed 49 and 35 bioactive compounds in extracts of N. calcicola and N. linckia, respectively. N. calcicola possesses the highest values of chlorophyll a, carotenoid, and total phenol contents in dry weight compared with N. linckia. After 100 days of tomato growth, the results showed the highest yield of tomato fruits with the application of N. calcicola and N. linckia compared with the untreated plants and the plants which were infected with Fusarium, suggesting that N. calcicola and N. linckia can serve as a new bioagent for biological control of the soil fungus Fusarium oxysporum f. sp. lycopersici (FOL).

Salinity is a major threat to crop production and global food security. Algae and their extracts containing bioactive compounds can enhance the salt tolerance of plants, including the salt-sensitive plants. The current study evaluated the efficacy ofThe online version contains supplementary material available at 10.1007/s12298-022-01176-6.

The present trial was performed to evaluate the effect of dietary incorporation of dried Spirulina, Chlorella and their mixture on the immune status of Nile tilapia (Oreochromis niloticus) before and after artificial infection with pathogenic bacterium Aeromonas hydrophila (A. hydrophila). Two hundred and forty fish were divided into four groups: (a) a control group fed on a basal diet only, (b) a second group fed on a diet containing Spirulina 15%, (c) a third group fed on a diet containing Chlorella 15%, and (d) a fourth group fed on a diet containing a mixture of both Spirulina 15% and Chlorella 15%. At the end of the experiment (9 weeks), the four groups were experimentally infected with A. hydrophila for 7 days. Antioxidant enzymes, lysozyme and bactericidal activities and histopathological changes were determined just before the challenge test and 7 days post‐challenge. Significant (p ≤ 0.05) increases in fish body protein% before the challenge test and increases in serum antioxidant enzymes, lysozyme and bactericidal activity in the Chlorella and algal mixture groups before and after the challenge test were observed. Spirulina, Chlorella and their mixture groups significantly decreased serum malondialdehyde compared to the control group before and after the challenge test. Using Spirulina, Chlorella and their mixture mitigated the necrotic and degenerative changes induced by A. hydrophila and revealed well‐developed and multiple melanomacrophage centres. Thus, dietary Spirulina, Chlorella and their mixture inclusion in Nile tilapia fish proved to have a protective effect against A. hydrophila infection.

The study focuses on the impact of foliar spraying cyanobacterium Spirulina platensis extract and the inoculation with the endophyte N2-fixing Pseudomonas stutzeri, and their mixture in the presence of different nitrogen doses on growth and yield of onion under field conditions. Bioactive compounds of Spirulina and Pseudomonas were analyzed by GC-MC and amino acid production of Spirulina by the amino acid analyzer. Hydrogen cyanide (HCN), indole acetic acid (IAA), ammonia (NH3), pectinase activity, and N2-fixation of Pseudomonas were measured. Plant height (cm), leaf length (cm), number of green leaves, bulb diameter (cm), fresh and dry weight of plant (g), chlorophyll a, b of leaves, bulb weight (g), marketable bulb yield (t. ha-1), cull bulb weight (t. ha-1), total bulb yield (t. ha-1), bulb diameter (cm), total soluble solids (TSS%), dry matter content (DM%), evaluation of storage behavior, and economic feasibility were estimated. Spirulina extract has several bioactive compounds. Pseudomonas can produce HCN, NH3, IAA, pectinase, and nitrogen fixation. The application of mixture with recommended dose of nitrogen increases the onion plant parameters, marketable yield, total bulb yield, bulb weight, bulb diameter, TSS%, DM%, net return, benefit-cost ratio (B:C), lowest cumulative weight loss% of bulbs during storage, and reduce culls weight compared with other treatments in two seasons. Application of S. platensis extract and inoculation with endophyte nitrogen-fixing P. stutzeri enhance the growth and productivity of the onion under different doses of nitrogen fertilizer.

We studied the impact of using fodder enriched with the cyanobacterium Spirulina platensis or the green alga Chlorella vulgaris or a consortium containing both of them on growth, biochemistry profile and immune status of the Nile tilapia (Oreochromis niloticus) fish. A set of 240 males challenged with Aeromonas hydrophila one week before the end of 9 weeks experimental period. The fodder supplemented with 15% (w/w) of Spirulina platensis, 15% of Chlorella vulgaris or 15% of their (1/1) mixture. Growth performance was measured all over 9 weeks. Challenge test was performed by infection with the pathogen after 8 weeks of growth. The serum total contents of protein, albumin, globulin, urea, creatinine and activities of aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase (ALK) and lactate dehydrogenase (LDH) were measured at 7 days before and after the infection. The results revealed significant increases in body weight of the Chlorella and their mixture (Chlorella and Spirulina) treated groups compared with the untreated control and the only Spirulina treated ones (p ≤ 0.05). Without infection, the serum total protein and serum globulin significantly increased by supplementation with the Spirulina, Chlorella and both compared to the uninfected control group. The serum albumin significantly decreased with Chlorella and the mixture supplementations. Lactate dehydrogenase (LDH) in the fish serum generally decreased with application of the enriched feed compared with the control. After infection, serum total protein and globulin significantly increased by the feed supplementations compared with the control group while the serum albumin insignificantly increased by supplementation with Chlorella and Spirulina. ALT, AST, ALK, LDH, urea and creatinine in the fish serum decreased with the microalgae additives compared with the control.

This study isolated and examined the performance of four selected strains of Rhizobium as growth enhancer inoculants of common bean (Phaseolus vulgaris) in saline- and drought-stressed fields located to the east and west of the Egypt Nile delta. Indigenous bean rhizobia were tested for salt tolerance by culturing and for taxonomic status by DNA analysis. Their nodulation and N2-fixation abilities under drought stress and persistence in biofertilizer formulations were evaluated, followed by assessment of their agronomic performance with common bean in 16 salt-affected, drought-stressed fields in combination with different doses of N-fertilizer applications in 2007 and 2008. Population dynamics studies with one model strain indicated good persistence in biofertilizer preparation. Inoculation with a test strain increased plant weight in the greenhouse from 2.718 to 3.314 g and four strains increased seed yield in saline/drought-stressed fields by 2.848⿿3.218 t ha⿿1 during seasons 2007 and 2008, respectively. Inoculation also increased straw production, harvest indices and the agronomic fertilizer N-use efficiency. The corresponding mean seed yields in adjacent uninoculated farmers⿿ fields exposed to the same intensity of aridification were 2.425 and 2.230 t ha⿿1, respectively. The study shows that locally-selected strains of rhizobia can be formulated into biofertilizers that significantly enhances seed yield and the agronomic N-use efficiency while providing a nature-based alleviation of the abiotic water deficit stress of intense aridification in saline- and drought-stressed fields.

Colonization of the rhizoplane habitat is an important activity that enables certain microorganisms to promote plant growth. Here we describe various types of computer-assisted microscopy that reveal important ecological insights of early microbial colonization behavior within biofilms on plant root surfaces grown in soil. Examples of the primary data are obtained by analysis of processed images of rhizoplane biofilm landscapes analyzed at single-cell resolution using the emerging technology of CMEIAS bioimage informatics software. Included are various quantitative analyses of the in situ biofilm landscape ecology of microbes during their pioneer colonization of white clover roots, and of a rhizobial biofertilizer strain colonized on rice roots where it significantly enhances the productivity of this important crop plant. The results show that spatial patterns of immature biofilms developed on rhizoplanes that interface rhizosphere soil are highly structured (rather than distributed randomly) when analyzed at the appropriate spatial scale, indicating that regionalized microbial cell-cell interactions and the local environment can significantly affect their cooperative and competitive colonization behaviors.