Role of Plant Growth-Promoting Rhizobacteria (PGPR) in Inducing Systemic Resistance in potato Plants Against The Fungal Pathogen Fusarium oxysporum f. sp. lycopersici

Abstract

This study aimed to evaluate the efficiency of rhizobacteria mixtures as biofertilizers in reducing the incidence of Fusarium wilt caused by the fungus Fusarium oxysporum f. sp. lycopersici in potato plants cv. Sponta, and determine the best control treatment. Three fertilizers were prepared using eight isolates of PGPR rhizobacteria, added at planting, after germination, and at ovulation. Readings of study samples were taken 45 days after infection. The activity of the peroxidase enzyme, the amount of total phenols, and the content of salicylic acid in the leaves were measured. In addition, peroxidase activity, total phenols, and salicylic acid content in the leaves were also measured. The severity of infection, disease index and reduction in disease incidence rate were also determined. The results showed the effectiveness of the studied biofertilizers in increasing the activity of the peroxidase enzyme and the leaf content of total phenols and salicylic acid in the leaves of potato plants infected with Fusarium wilt following all treatments, with significant differences compared to the infected control, and reduced disease index and severity of infection with Fusarium wilt. The treatment with the mixture of eight bacterial isolates and repeated addition (M3D4) outperformed the rest of the treatments and gave the highest values in peroxidase activity (0.19 µmol/mg), and the highest content of total phenols (79.69 mg/100g) and salicylic acid (176.61 μg/mg) in the leaves of potato plants compared to the infected control (0.1, 45.01, 107.12, respectively). The infection rate and disease severity were also reduced with significant differences compared to the infected control, and the M3D4 treatment produced the highest infection reduction rate of 82.33%. These results confirmed the effectiveness of mixed inoculation with eight isolates of PGPR rhizobacteria, upon repeated addition, stimulating systemic resistance in infected potato plants infected with F. oxysporum, thus the possibility of using these types of rhizobacteria in biocontrol programs against this fungus is recommended.

Keywords:

Rhizobacteria, plant growth promoting rhizobacteria, PGPR, bacterial biofertilizers, potato, Solanum tuberoseum, productivity.