Impact of the microalga Dunaliella salina (Dunal) Teodoresco culture and its ß-carotene extract on the development of salt-stressed squash (Cucurbita pepo L. cv. Mabrouka).

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 ß-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 ß-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 ß-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 ß-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. Supplementary Information: The online version contains supplementary material available at 10.1007/s12298-022-01176-6.

Biological control of Fusarium tomato-wilt disease by cyanobacteria Nostoc spp.

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).

Maximizing growth and productivity of onion (Allium cepa L.) by Spirulina platensis extract and nitrogen-fixing endophyte Pseudomonas stutzeri.

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.