Inhibitory Activity of Plant Growth Promoting Rhizobacteria in Control The Pathogens of Cucumber Root Rot Disease in Babylon Province

Abstract

The study aimed to identify the Cucumber  Root Rot Diseases in some areas of Babylon Governorate, isolate and diagnose the pathogen. The evaluation of the efficacy of Azotobacter and Azospierillum in disease control under field conditions. The field survey results showed cucumber root rot disease in all areas covered by the survey, with infection rates ranging between 70-90% and severity from 30-68%. The isolation results showed the presence of 10 types of fungi associated with the infested roots of the cucumber plant. Fusarium Solani was the most frequent fungi. It appeared in most samples with varying frequency rates of 75.05%, followed by the fungi Macrophomina Phaseolina 68.75% and  Rhizoctonia Solani with a frequency of 62.05%. The use of Azotobacter Chrococcum as a biological control agent inhibited the growth of the pathogen Rhizoctonia Solani (Rs-1) and Fusarium Solani (Fs-6) and Macrophomina Phaseolina (Mp-2) in the PDA medium. With a high inhibition rate. The field experiment results showed that the agents used might significantly reduce the adverse effects of the pathogenic fungi.  They also provided good protection for cucumber plants from infection with root rot pathogens, with significant differences from pathogenic fungi alone, whose infection rate was 100% and intensity was between 87.67 - 95.67% in the interaction treatment. Chroococcum and Azospirillum Brasiliense were superior in reducing infection incidence and severity with cucumber root rot pathogens under field conditions. It provided good protection from infection so that the disease incidence was between 22.00-27.00% and the infection severity 20.00-21.33%. All the treatments significantly increased the studied cucumber plant growth parameters, increasing plant height, fresh and dry weight, leaf area, and yield weight. Azospirillum and Azotobacter alone and without adding the pathogen to improving plant growth parameters and increasing the yield weight. The interaction treatment between the two types of bacteria surpassed the highest rate of 36.04 kg compared to the control treatment and without any addition, as the yield weight reached 20.12 kgs.