الفهرس 
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Abstract
The study aimed to determine the effectiveness of some bacterial and fungal genera as environmentally friendly biological control agents to control the fungus Rhizoctonia solani,
which causes black scurf disease in potatoes, where the potato crop is considered one of the most important export crops. The researcher obtained the results as follows:
1- The fungus R. solani was isolated from potato plants showing symptoms of black scurf disease, collected from governorates El Beheira and Alexandria, and 6 isolates of the causative
fungus were obtained.
2- Some microorganisms were tested in the present study as biocontrol agents against the causal agent of scurf disease, as follows:
a- Bacillus subtilis (Bac1) was isolated from healthy potato plants, and isolate (Bac2) was obtained from potato cultivation soil.
b- An isolation of the fungus Trichoderma album was obtained from Kafr El-Zayyat Company for Organic Technology Compounds.
c - Saccharomyces cerevisiae (a commercial product) was used.
3-a- The fungal isolates were defined morphologically, and the identification of the isolates was confirmed by molecular methods, where the DNA was extracted. A polymerase chain reaction
(PCR) was performed. The result of the PCR reaction showed a bundle of DNA with a length of 629 bp.
- The nucleotide sequence of the samples that gave a specialized band length of DNA was determined. The sequences between the tested isolates of R. solani, and the registered ones in the
98 gene bank (National Center for Biotechnology Information) of the same species were compared.
The molecular identification of the tested isolates was confirmed by 87-98%, then the phylogenetic tree was prepared.