Control of Chickpea Root Rot Disease by Rhizobacteria in a Greenhouse

Background: Chickpeas are a prevalent and significant crop in the agricultural sectors of northern Iraq. In recent years, production has significantly declined due to diseases affecting chickpea plants. Investigating the pathogenic fungi responsible for these diseases is essential to restore production levels to their prior and improved states. Methods: Samples of diseased chickpea plants were collected from fields in the Erbil, Sulaymaniyah and Salah al-Din governorates in northern Iraq. Isolated associated fungi led to the identification of the dominant pathogenic species. A pathogenicity test was performed on the fungal isolates, showing the most aggressive strain for subsequent antagonism testing against three rhizobacterial isolates: Azotobacter chroococcum, Bacillus cereus and B. pumilus. This testing was conducted both in vitro and in a greenhouse setting, using single treatments and combinations. Result: The results showed that the pathogenic fungus Rhizoctonia solani was predominant, with the strain Srs-21 exhibiting the highest virulence in vitro. The three rhizobacterial isolates, A. chroococcum, B. cereus and B. pumilus, showed high efficacy in inhibiting the pathogenic fungus in vitro on potato dextrose agar (PDA) medium. In the greenhouse, the triple bacterial interaction treatment showed a seed germination rate of 100% and diminished disease incidence and severity to 0%, in contrast to the positive control treatment, which recorded 90% and 70%, respectively. It also showed the highest rate of rise in the dry weight of plants, signifying enhanced growth metrics.