TITLE [EFFICIENCY OF SOME TYPES OF BACTERIA ASSOCIATED WITH CUCUMBER ROOTS AGAINST THE RHIZOCTONIA SOLANI]

This study was carried out in the laboratories of the Plant Protection Department, Ministry of Agriculture, to isolate bacteria associated with cucumber roots from greenhouses in Baghdad, Salah al-Din, Sulaymaniyah, and Basra, and to evaluate their ability to inhibit Rhizoctonia solani, the causal agent of cucumber root rot, on Potato dextrose agar ( PDA) medium. A total of 12 bacterial isolates were obtained from healthy cucumber root-associated soil. These isolates varied in type depending on collection site and environmental conditions. All isolates demonstrated high inhibitory activity against R. solani, with fungal colony diameters ranging from 1.17 to 6.63 cm and inhibition rates between 26.3% and 87.0% compared to the control. Molecular identification using Polymerase Chain Reaction (PCR) was performed on three isolates: Bacillus cereus, Bacillus thuringiensis, and Bacillus rugosus. Their nucleotide sequences were submitted to the GenBank database under accession numbers PP935479.1, PP935461.1, and PP934669.1, respectively. These findings highlight the potential of native bacterial isolates as biocontrol agents against cucumber root rot.