AbstractThe focus of this research is to evaluate the performance of Bacillus, Pseudomonas, Azotobacter, and Azospirillum for their plant growth abilities in vitro and in vivo. The best performing bacterial isolates from preliminary screening (in vitro) were able to produce indole acetic acid (IAA) and gibberellic acid (GA3) of 0.25–22.63 and 5.9–31.8 μg ml–1, respectively, eight best isolates were further tested for their efficacy in promoting crop growth and yield of tomato (Lycopersicon esculentum Mill.) by different application methods namely seed coating, soil application, and seedling root dip method. The factorial data analysis provided evidence that the interaction of bacterial isolates and different inoculation procedures together generated better yield in the greenhouse pot experiment. The findings suggest that the inoculation of Azospirillum strain ASP25 by seedling root dip method produced greater yields. Correlation and regression models hypothesize that all the variables are positively correlated with yield at P < .01 and growth variables like number of fruits per plant (r2 = .886), shoot length (r2 = .695), and root volume (r2 = .554) at P ≤ .0001 contribute to the yield parameter individually and by multiple regression model all the plant growth variables together increased fruit yield per plant by 89% (r2 = .899). These results demonstrate that a high yield is always linked to a healthy vegetative development. However, as technology in agriculture progresses, the proposed method points to the usage and development of computer applications to estimate crop output.