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Fusarium head blight is an important disease of durum wheat which requires several fungicide treatments of seeds to achieve satisfactory control. The current study was carried out to evaluate commercially available fungicides in vitro for their efficacy against eighteen Fusarium spp. isolates collected from different fields in the north-eastern part of Algeria. The morphological and molecular characterization reveals the presence in wheat seeds of the main species complexes F. acuminatum, F. equiseti, F. avenaceum, F. solani, F. culomorum, F. incarnatum-equiseti, as well as F. tricinctum species complex and F. chlamydosporum species complex. Antifungal activity of fungicides shows that all triazoles tested have proven their effectiveness in inhibiting the mycelial growth of various strains of Fusarium tested. However, their sensitivity varies between them significantly (p<0.05) depending on the dose applied and period of exposure to each fungicide. The results showed that tebuconazole (Raxil and T?buzole) and the combination fludioxonil + difenoconazole greatly reduced the mycelial growth of Fusarium isolates by 84.31%, 82.94%, 81.33%, respectively, as compared to difenoconazole alone (73.16%) at the recommended dose after five days of exposure. Regarding their effect on conidia germination, tebuconazole was more effective than fludioxonil + difenoconazole, which leads to deformation of cell wall structure and fragmentation of conidia. These results will provide useful information to select suitable fungicides for seed treatment and management of wheat head blight disease.

The present work was carried out to enhance biomass production of Spirulina (Arthrospira platensis Gomont) in a modified medium and to investigate “in vitro” its ability to produce antimicrobial substances against pathogenic bacteria and phytopathogenic fungi. The antibacterial activity was evaluated by the solid medium diffusion method on two pathogenic bacteria (Bacillus cereus & Klebsiella sp.), And the antifungal activity was evaluated on three phytopathogenic fungi (Alternaria solani, Cladosporium sp., Fusarium culmorum). The antibacterial test showed that the aqueous extract produced by S. platensis was more active against Gram-positive than on Gram-negative bacteria, the highest antibacterial activity was recorded against Bacillus cereus. Moreover, the Antifungal test showed that the aqueous extract was active against all three tested fungi and the highest antifungal activity was recorded against F. culmorum with over 90% inhibition of mycelial growth. The results of this research proved that cyanobacteria could be a good source for the production of antimicrobial agents which could be effective when compared with contemporary antimicrobial compounds and it can be used in the Biocontrol of several plant fungal diseases.

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