https://doi.org/10.37229/fsa.fja.2024.03.21

The use of Rhizobium strains as plant growth promoting rhizobacteria (PGPR) is rapidly expanding in vegetable crops in recent years. In the current study, three Rhizobium strains were examined as a PGPR in two experiments with zucchini squash (Cucurbita pepo L.) cultivated in the spermosphere model and greenhouse soil respectively. The spermosphere model to ensure that microbial cells enter the zucchini root. This was verified by counting rhizobia cells in a specialized environment. After that, an electron microscope was used to observe the changes that bacteria make when penetrating the plant roots walls. All rhizobial strains were assessed for features that promote plant growth. All strains synthesized indole-3-acetic acid (IAA), with the greatest concentration seen in R. leguminosarumbv. trifolii (61.18 μg mL⁻¹), which also exhibited peak siderophore production (21.58%), phosphate solubilization (92.00 ppm), and ammonia synthesis. All strains exhibited the synthesis of protease and hydrogen cyanide. The results demonstrate that the evaluated rhizobia exhibit various PGPR characteristics and have promise for application as biofertilizers in sustainable agriculture. Additionally, seed inoculation with different Rhizobium strains enhanced both fresh and dry shoot biomass of zucchini in comparison to the uninoculated control and significantly increased the phosphorus concentration, demonstrating the potential of rhizobia as biofertilizers.