A number of 35 fungal isolates were recovered from root tissues of cucumber plants displaying root rot syndromes at Dere'iyah region, Riyadh district. These isolates were classified as belonging to 4 species, namely: Aspergillus niger, Fusarium oxysporum, F. solani and Rhizoctonia solani. The four species were different in their prevalence as well as in their relative pathogenicity to cucumber both in vitro and in vivo. F. oxysporum and F. solani exhibited higher infective potency than the other 2 species. On the other hand, two highly antagonistic isolates belonging to Bacillus subtilis, and Trichoderma viride, were isolated from the rhizosphere of healthy cucumber plants. These prospective antagonists were tested, in vitro and in vivo, for their suppressing potency against the highly virulent F. oxysporum and F. solani isolates. The results revealed that both B. subtilis MB10 and T. viride MT15 were able to eliminate the deteriorative abilities of the two phytopathogens, indicting that these prospective antagonists hold some promise in the biological control of root-rot disease of cucumber.
Key words: Root-rot, cucumber, Fusarium oxysporum, F. solani, Bacillus subtilis, Trichoderma viride.
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