Thesis (Ph.D.) - Cairo University - Institute of African Research and Studies - Department of Natural Resources

The present study has been conducted to explore the antifungal potency of the crude extracts and powder of seaweeds collected from Alexandria, Port Said and Damietta cities in Egypt. Macroalgae were identified as Ulva fasciata, Gracilaria confervoides and Enteromorpha flexuosa. Three soil borne fungi, Fusarium solani, Rhizoctonia solani and Macrophomina phaseolina infecting cucumber plant were subjected in this study. The extracts of the three algae showed different reduction rates on the mycelial growth of F. solani and R. solani on Potato Dextrose Agar medium (PDA). More clearly, the results indicated that the highest reduction (21.25%) and lowest reduction (9.4%) was showed by G. confervoides on R. solani and by E. flexuosa on F. solani, respectively. However,no reduction rate was noticed on the mycelium growth of M. phaseolina but growth malformation was recorded (arial mycelium and no microsclerotia formation), by the three macroalgae. Under greenhouse experiments, it was noticed that the combination of the three macroalgae powder showed better results. Where, the results indicated that the lowest dead plants was recorded as (8.3%) when combination between the three algal powders was applied in soil infected with M. phaseolina as well as the vitavax fungicide treatments, followed by 16.7% at combined treatment of G. confervoides and E. flexuosa in soil infested with R. solani. Also, application of G. confervoides in infected soil with M. phseolina showed the highest dry weight (43.7g) compared with the control treatment of M. phseolina (15.0g). Most importantly, it is interesting to note that the combined three algae increased cucumber yield as 58.4,177.1 and 160.8g comparing with 25.3, 25.2 and 25.2g for plants inoculated with R. solani, M. phaseolina and F. solani, respectively

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